DOCTORJL DISSERTATION SERIES

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N itltlSM STATS COiL d a t e

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u UNIVERSITY MICROFILMS

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ANN ARBOR ■ MICHIGAN

THE INFLUENCE OF SOIL FIXTURES ON
TURF GRC,;TH AND

SOIL STABILITY FOR IIIu KV.'AY

SHOULDERS Ai'ID AIRPORTS

by

SAIL C. BLCLftUIST

A THESIS
Submitted tc the School of Graduate Studies of Llchi
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the cegroe of
DOCT O R OF PHILOSOPHY
Department of Agricultural Engineering

AC LDOV- LED G. SLIT

The author wishes to exp re s s his appreciation to
Professor E. H. Kinder t
*ind Dr. C. L. Harrison for their
guidance and assistance throughout the
investigation.

c o a r s e

He Is also indebted to hr.

of this

E. A. Finney,

LI chi fan State Highway Department and tne Soils department
of Lichifan State College for their assistance in conduct­
ing, preparing

.*01d

main tain Inf the grasp plots and the

accomplishment of the tests.

TABLE OF CONTENTS
pa^e

I

Introduction ........................................

1

II

Review of Literature

5

III

Test Plot E x p e r i m e n t s ............................... 10

...............................

1.

Experimental Test Plots
Description of Soil m a t e r i a l s .................14

2.

Turf (Growth........................................ 19

3.

Turf C o v e r a g e ...................................... 25

4.

Stability of Turf P l o t s ........................ 30
a.

Plate Bearing Plots

b.

Rutiing T e s t s ................................. 34

c.

Penetrometer Tests and Correlation . . .

a.

(Graphical C o r r e l a t i o n s ......................51

.....................

51

38

IV

C o n c l u s i o n s ........................................

59

V

Suggestions for Future Study ......................

63

VI

Literature Cited ...................................

64

VII

A p p e n d i x ............................................

57

INTRODUCTION
There has b e e n widesore&d
uses of grasses,

interest

of varying characteristics,

struction and maintenance of highway
also

in the specialized,

shoulders and berms and

for the construction of landing,' strips,

small air parks.

The value of

been r e c o i l zed for many years,

for trie con­

on itirf ield s and

turf for h i g h w a y shoulders lias
but v a r ying results have lead

to d issat isfaction on performance and maintenance.
the World W a r II emergency,
was recognized and practiced

During

value of turf lan ding
from necessity and its

strips

success

will un doubtedly lead to w i d e r civilian use of turn* for lanc­
ing strips and small air parks.
W i t h the wide variation of climatic conditions and soil
types encountered

throughout

very close a t t ention need

trie country

be given

species of grasses or legumes best

it is obvious

to trie selection of the
suited

for revegetating

hi g h w a y shoulders and berms as well as a i r f i e l d sites.
widespre ad

Interest

struction materials

that

The

in the use of {grasses as valuable con­
is evidenced by t.neir use in experimental

as well as functional projects by the B u r e a u of P u b l i c Roads
and various State Highway organ!zations.
W i t h these factors in mind a study was initiated
for the study of
tures available

the growth of grasses on various
for* construction of highway

sequently airstrips and air parks,

in 1944

soil mix­

shoulders -and con­

in hiohlgnn.

This was a

cooperative project between the Soil Science Department of
Michigan State College and

the Michigan State Highway Depart­

ment, Research Laboratory.

This thesis Includes data from a

previous progress renort on "The Study of Turf Growth of Sell
Mixtures Available for Highway Shoulder Construction in
Michigan" prepared by Professor J. Tyson,

Soil Science Depart­

ment, Michigan State College and Mr. E. A. Finney, Michigan
State Highway Department.

This progress report was published

by the Ilignway Researcn Board., Report of Committee on Road­
side Development,
data,

Ji7th Annual meeting,

September 19 *±8.

graphs and summaries of tne above mentioned

The

report nave

been included in tnls ..orK as background material and where
applicable nave been brought up to date.

All work subsequent

to ld-±7 was under th * authors direction and supervision.
The main object of the study was

to determine

the effect

of mixing the various amounts and kinds of soils into the top
six Inches of the commonly employed sand and gravel
base courses or shoulder materials,
and also upon

subbases,

on growth of various grass

the stability of the shoulders produced with the

varying soils and grasses.
The report includes a description of the test area,
discussion of the turf development on wirioup

and

soil mixtures.

In addition,

methods of conducting stability tr^ts,

penetro­

meter tests,

density tests and c jrrelat ive studies on the .In­

dividual grass plots are discussed together with tne test
re suit s.

The soils selected for the mixing with the sand and
gravel subbases or shoulder materials were these commonly
available for this purpose in southern l.lichlgan areas.

The

grasses selected were representative of commonly used var­
ieties and which were believed to conform to the following
characteristics:
1.

Ad&oted to local soil and climatic conditions.

2.

Resistance to wear and rutting-.

3.

Rapid recovery following abuse.

4.

Drought resistant.

5.

Low maintenance c o s t 0.

It is evident from the requirements that very few if
any,

available commercial grasses meet all of the above re­

quirements.

Very limited data was available on wear tests

o r loading tests on grass sods or turfs.
The results of the test sections indicated that Chewing
fescue was an excellent grass to plant on shoulder and runway
surfaces stabilized with sandy or gravelly material.

The

later tests shoved very good results of carrying capacity on
sections in which quack grass crowded out

She original grass©

This can be attributed mainly tc its widespread root-basket
and heavy top growth which flourished on all soil types and
climatic factors involved in the test.

Topsoils consisting

of miami loam, Brookston loam and Bell efontaine sandy loam
can be satisfactorily mixed v/ith sanas and gravels to produce
a turf, wnile clay and peat had varying results.

Chewing

fescue was best

suited when planted wi t h small amounts of

nurse-grass to aid In starting and pr o t ecting the slower
growing fescue.

A n excess of the so-called nurse-grass was

detrimental to the establlshment of a cover of Chewing fescue
since

the nurse-gruss flourished the first year following

quick g e m i n a t i o n
the second and

and died out leaving a sparse cover of fescu

subsequent years.

Fertilizing and reseeding

were required to maintain a good stand.

The results herein

are not based on emy reseedlngs or additional fertilization
since attempts were made to minimize any and all variables
to obtain analyzable data.
The rutting tests indicated that none of the soil mix­
tures under study do possess
istics when wet.

satisfactory stability character­

W h e n all factors are considered the data

would indicate that the pr ocessed gravel,

22-A,

is the beet

of all the so11 mixtures in relation to stability and turf
growth.
The study of the load bearing tests and penet rometer
studies indicated a definite

relation whereby dependable data

can be obtained with special penetrom eter
bearing values of greater magnitude.

to predict load

Two correlative studies

are included w h ich are d i f ferent in nature and both prove
valuable ana dependable
test

in predictions.

In each case of the

series both penetrometer and load b e a r i n g tests were

taken to insure close correlative studies.

R E VIEW OF LITERATURE
Observations made on grass plots established at the
Agricultural R e s earch Center,

Beltsville, Maryland

dicated th«s.t creeping red fescue,

(1)

in­

chewing* s fescue and

Kentucky blue grass were most desirable from the standpoint
of both wear resistance under wimpled traffic and the^r
ability

to recover raridly following abusive use.

Results of investigators on physiological effects of
differential cuttings, ^nr1
Investigations cf fescue,

H i nation agre° verv closely.
bluegrass,

and bentgrass under

three cutting heights w»re made t>y H arrison (23).

These ex­

periments p r oved the root caraclty rer! action of low cut
grasses and

that applications of mineral fertiliser did not

overcome the effects of low cutting.

C-raber (24)

found blue­

graso could withstand close clipping for one or two
with good results,
of Kuhn anc Kemp

seasons

but declined productivity resulted.
(25)

and Lovvorn (26)

Works

p r oved close clip­

ping of grasses reduced growth of foliage,

roots,

and rhizomes.

The value of cutting data p rov e s important on many grasses for
shoulders and airstrips

Flnce they are dependent on root

growth for load carrying capacity and rutting resistance.
In studies by Llorrlsh (1)

he concluded that the optimum

dates for seeding grasses in this area were early spring or
late

summer and e^rly fall.

June

- 5 -

seedings were i n f erio r and

unsatisfactory.

Tests conducted on the plots of this work

indicated no variations in the plate bearing' values of any
consequence on the various seeding times or rates.
Table III contains this data.

Appendix

This study wa s made outside

the original p r o b l e m to Investigate b e a r i n g values relative to
seeding times.
Physical analysis of soils by Humbert and G-rau (27)

in­

dicate that soil mixtures containing approximately seventy per
cent sand are best for the growing of grass with o p t i mum of
foliage and root production.
The results of traffic tests at LlacDil"! Field,
(2)

Florida

in 1946 on a bermuda grass shoulder adjacent to pa ved run­

way surfaces indicated

that deformation of the surface of the

soil was in direct relation to the load repetitions the sur­
face was expored to.

Similar results were obtained in tests

at Maxwell Field, A l a b a m a (3)

under the same conditions of

loadings.
A series of load b e a ring tests (4)
bluegrass

carried out on Kentucky

scde at four airfields in Ohio in 1943 indicated that

turf provided a very definite advantage to soils cn load carry­
ing capacity u n der conditions of saturated

subbases.

The

tests

were carried out or. the soil s when they were at or near their
plastic limit.

The advantage was attributed to the condition­

ing of the subbase by th<=* sod cover.

Some investigators have

indicated that after a certain number of repetitions of a given
load the soil will, become perfectly elastic in its behavior

_

b

_

(5)

( o ) , h o w e v e r farther I nvestigat ions cannot Justify,

in limits,

with­

these indications (7).

Yield p o int a nd b e a r i n g capacity studies b y H o u s e l (B)
indicate

that soils o r subbases

supporting loads b a s e d upon

yield point v a lues will not yield to f u r t h e r pro g r e s s i v e
settlement s.
In recent years,

load tests to measure b e a r i n g capacity

of soil m a sses h a v e become of Increasing Importance in engine­
ering practice and,
cedures,

in spite of a wide di v e r s i t y of test p ro­

they strike the p r a c t i c a l mind as a direct and ob­

jective approach to a m a j o r p r o b l e m for w h i c h there has been
no generally a c c epted analysis.

The choice

size a n d shape are controversial points.
for m a n y years
mechanics,

of b e a r i n g area

It has b e e n believed

from the wor k of early investigators in soil

and more r e c ently from i n v e s t igatio ns

of Housel ( b ) ,

Hubbard and F i e l d (14), C a m p e n and Smith (15)

(15),

T e l l e r and

S u t h erland (6), I.:i&dlebrooks and B e r t r a m (17)

and others,

that

the size of bearing plate m a t e r i a l l y I n f l uences the magnitude
of the unit l o a d w h i c h is supported at a given deflection.
Recent

investigations have

shown that the size of the bearing

area ceases to h ave an In fluence on the m a g n i t u d e of the unit
load supported at a given d e f l e c t i o n if the d i a m e t e r is of
relatively large d i m e nsion (18).
W o r k done by Groldbeck and Bus sard. (19)

e s t a blis hed that

when a given unit of load is applied to a soil o v e r various

- 7 -

areas,

the depth of penetration is directly proportional to

the square root of the area over which the load is applied.
Undoubtedly the major problem with the most uncertainty
of load testing is the translation of test data into working
design data.

Burmister (20)

maintains

that the methods used

to interpret and apply the results fall into two gener«l
classes,

1) E o u s s i n e s q ’s (21)

H o u s e l ’ e (8)

theory of elasticity and 2)

empirical relationships.

Bousslnesq's theory

applies on soils following the elastic properties closely while
Housel* s analysis applies on many types of soils not following
the elastic properties and t h eor1
From studies it is evident that the hearing capaci**^ is
proportional to the reciprocal of the radius of the bearing
area and directly proportional to two soil constants,

the

values of which are determined b y making load tests on two
different sizes of bearing areas (20).

The most important

fact to be noted Is that bearing capacity is not a simple in­
herent property of soil but must always be defined in terms
of some allowable

settlement considered to be satisfactory for

a given set of conditions.
The American Society of Civil Engineers committee on
Sampling and Testing have based a study on soil bearing values
on the assumptions that the loaded material is clastic, homo­
geneous,

isotropic and of infinite depth.

None of these as­

sumptions are exactly true for a single application of load

however.

From these relationships and from equations of th'~

T h e o r y of Elasticity,

If the plate b e a r i n g tests agree vriih

the clastic equation,

the unit load P / A p l o t t e d against

the

ratio of settlement to dlrjneter should result in a straight
line and be independent of the size of the plate ( 2 2 )•

- 9 -

TEST P LOT E X P E R I M E N T S
EXPERIMENTAL

test

plots

The surface 3oil was remove d from the test area,
m e a s u r e d forty feet wide and n i n e t y - s i x feet long,
forty-eight p l o t s of equal

size.

which

containing

This wa s a c c o mplish ed with

a bu l l d o z e r scalping off appr o x i m a t < L y one foot of soil to
insure

removal of all roots and top soil.

c o n s i s t i n g of;
gravel,

and

1)

incoherent

sand,

2) g r a d e d sand,

was p l a c e d in p a r a l l e l

inches deep a nd ten feet wide

transversely o v ^ r the
The additive

loam top soil,

four strips of g r a n u l a r

soil materials c o n sist ed of Lilami
subsoil clay anci peat

stripping from a gravel deposit in­

cluding top soil and the h e a v i e r B horizon.
the test nre=

sections.

spread in bands eight

B r o o k s t o n loam top coll,

mixture and B e l l e fontaine

strips eighteen

in n i n e t y - s i x foot long

The additive soil m a t e r i a l s we^e

materials.

3) pit-run

1) p r o c e s s e d gravel - 22— A I.ilchigan State Highway

specifications (11)

feet wide

G-runular material s

showing the location of the

The layout of

granular bas e m a t e r ­

ials a n d the v a rious kinds an d p e r c e n t a g e s of the soil ad­
ditives can be n o t e d in F i g u r e 1.

A general view of the

test

area during the cons t r u c t i o n a l phase is shown in Figure 2.
can be n o ted that

the stripped topsoll

It

from the area I f de­

p o s i t e d adjacent to the test sections and it was later sloped
o f f from the test

sections w h ich were

- 12 -

slightly elevated over

PLAh OF

5G j.L PLOTS

E a c h Plot 10 Feet by 8 Feet

Pit R u n Gr&vol
Incoherent
SanG-D une

Prcceseed
Gravel
o
./
*•• »
»

Parent Laterial
F o x - B e 11 e fcntalne

Gr aded
Sand

Spec.

C -H orlzon
( 1)

(4)

g

20/o

( 15)
OG/O

15/0
( 33)

( 27)
oO/o

2o}o

O'J/0

(IS )

( 28)

(

-0)

lO/o

10/0

10,0

7:.o
(5c)

( 26)
id0/O

(3)

o

10/O

(14)
10/i/

2 2—
A
( 57)

10/O

( 2)

•H

(25)

(13)

10yo

">•

7/(?

O
j
(
o
o

(17)

5)
20/o

G
w
( 6)

30/o

10 /o

a>
G
•Hi—
1
.s tH
4-3

Peat
5/o

( 42)
30/b

30/b

(45)

(31)

Clay

Peat

10/3

5/0

Clay

P eat

Clay

10>o

5/0

1C>

10/is

(20)
15/3

10,o

15,5

10; a

l5>o

(=0
25/O

15/3

( 21)
25;o

1 5;o

(33)
25;o

15/o

( 45)
SO,n

( 32)

(2 7)
50/3

( 1 2 )

O
PQ

(36)

( 2 ^ )

lU'J/o

(47)
75

75>o

75,3

10 Ojo

I . . .

Figure 1
11 -

15,o
cO; o

OO/o

( 35)

( 23)

( 11)

Vi (X
<
DO
i—
1 EH
i—
I

10; o

( 45)

( 34)
50/b

Peat
5/0

( 4-±)

o

o

7 5>o

(6 )
15 /O

( 10)

G rfi

1 5/j

( 30)

(19)

( V)
>s
a?
4-3i—
(
llJ o
<
u
a* rG
c
aj

20/o

( is )

Cla y

( 41)

( 29)
20;o

75,o

j

(

10

v

2. 0

)

1 J '.J;0

> *

--A

r i

; wil' O

£

the original ground contour to provide adequate drainage as
well as simulate1 shoulder conditions In the field.

It can

also be noted In Figure p that portions of the test sections
were to be shade5 partially and this v/cul " also simulate fi eld
conditions.

There was no evidence of effects of shading; noted

in the studies in either turf growth nor on sheltering; effects
on moisture percentages.
The soil additive materials were Incorporated into the
top six inches of the granulr.r base materials by hand mixing
with shovels to insure complete blending of
to a six inch depth.

The material e were

down

then compacted by re­

pented passes with a cult lt>acker, pulled by a four wheeled
tractor,

until no further consolidation war evidenced.

This

method of compacting- was employed to follow an closely as
possible current field practices of shoulder construction in
highway practices.

Further testing; on new sections would ad­

here to current compaction and mixing practices which might
vary slightly with location and period.
Following the mixing and compacting processes,

fertilizer

of a 10-5-4 ratio was broadcast over the test area at the rate
of five hundred pounds per acre.

A grass seed mixture composed

of equal parts of Kentucky blue grass, Chewing fescue,

and

domestic ryegra.se was sown at the rate of +,orty pounds per acre.
The fertilizer application was repeated about April first of
each year,

for the next three years at the same rate.

- 13 -

The

grasses were allowed to grow without mowing through the first
fall,

1944,

and since that tlrae have been nowed four to six

tines each season to simulate mowing operations on highway
shoulders in the field or on airstrips or air parks.

The mow­

ing was accomplished with a eickle-bar rno'-er and no cuttings
were removed by raking.

The original test section fertilizing

and plantings were accomplished In August 194a.
DESCRIPTION OF SOIL LATLRIALS
The so11 materials employed in this study were obtained
locally and are described as follows:

(9)

111 ami series: Liaml 1= a w-ll-drained clay soil ranging
in texture from a loam to n silt loam occurring in un­
dulating to rolling moraines and on till

plains.

The

soil is slightly plastic find easily compacted when moist
hard, and dusty when dry,

and soft and esl * ck when wet.

The soil falls in tne a - o group of th" Public Roads
*

Administration Soil C 1 « Q° 1 fica.t Lon and in the L— 6 group
under the Civil Aeronautics Adininletration classifi­
cation.

(10)

B rooks ton serl es: Brooks ton soils are characterized *-s
poorly drained clays and range in texture from loam to
clay loam.

Tii^y rre found on till plains and. basin are*

Soil may be stony and cloddy.

Under normal conditions,

the soil is soft to plastic but will become tough
h a v\i when allowed, to dry out.

and.

This soil falls in the

A - 6 group of the P u b l i c Roads A d m i n l F t r a t i o n

soil class­

ifi cation anc1 in group E — 7 of the C i v il Aeronautic''
class i f i c a t i o n system.
B e lle font alne

series; The surface of Be 11 e f o n t a i n e

In texture from sandy loam to loam.
c haracter ized by Its
a m i x t u r e of e m d ,

ranges

The " B u h o r izon is

reddish brown color and consists of

g r a v e l and clay.

Is ample to render t h e mass

The q u a n t i t y of clay

sticky when moist;

a t e l y cemented or h a r d when dry.

The

and m o der­

surface relief

varies from undu lating to smoothly rolling and hilly.
This soil Is normal ly found in e skiers and m o r a i n e s and
gravel deposits are common.
group of the Puhli°
cation and

The soil falls in the A-l

R o a d s A d m i n i s t r a t i o n soil classifi­

in the 2— 6 group of the Civil A e r o n a u t i c s

A d m i n i s t r a t i o n classifica tion system.
F o x seri ^ s ; The surface

soil of F o x ranges

loam to loam in texture.

from sandy

The fox soil is similar tc

B e l i e f on talne but ma.y be dist i n g u i s h e d from it by its
o c c u r r e n c e on rnor« n e a r l y 1^'el terrain,
un i f o r m i t y of the " B 1* horizon,
etratum o^ stratified gray

and a uniform sub-

sand and gravel containing

a high percentage of* calcareous material.
falls in

the A - 3 group of

soil classification

lb

The

soil

the P u b l i c Roads A d m i n i s t r a t i o n

and in group

nautics A d m i n istration

by a g r e a ter

2-2 of the C i v i l Aer o ­

c l a s s i fication system.

Incoherent

san'l;

C o l o m a soil
tc a loamy

This m a t er ial was obtained

from the

series w h i c h ran^^p in texture from a sand
rand.

Th° m a t e r i a l is loose,

in w a t e r h o l d i n g c a p a c i t y and
outs and wind erosion.

r e l a t i v e l y 1-,,T

is h i g h l y subject

to blow­

It is n o r m a l l y fcurh4 on undulat­

in g to r o l l i n g terrain a s s o c i a t e d c l o sely with morain ic
formations.

This

series falls in group A — 5 of the Public

R.oads A d m i n i s t r a t i o n

soil c l a s s i f i c a t i o n and in group

E — 2 of the C i vil A e r o n a u t i c s A d m i n i s t r a t i o n classlficatlc
system.
Graded S a n d : Washed
from coarce

sand from a local

source,

to very fine material.

P i t - r u n g r a v e l : This m a t e r i a l co nsisted of the
zon of the B e l l e f c n t a l n e

ing clay b i n d e r material.

ph y sical

s u r f acing a gg r e g a t e s lack­

The m a t e r i a l contains crushed

and rounded a g g r e g a t e c o n f o r m i n g to g r a d i n g and
r e q u irements of the M i c h i g a n State H i g h w a y

Department

standards

(11).

C l a y : This m a t e r i a l was
of the h i ami

subsoil clay from the "C" hcritoi

series.

P e a t : W o o d y poaf

from a local deposit.

The p h y si cal c h a r a c t e r i s t i c s of the various
he*vc been
soil

"C" hori­

series o b t a i n e d locally.

P r o c e s s e d ? 2 - A G r a v e l : Road

gravel,

w h i c h grade

summarized in Table I.

series employed

soil materia'

Typical p r o files from

in the test are shown in Table II.

16

—

the

TABU T
maauRY or son. m a t u a l

axausis

BSreT n T K T B S r
Mlaal Surfaaa Sail Braafcataa Strfhaa Soil
22-A
Pan*Belief
A-B Horitsa
M.S.B.D.
Ap B Barltw
C Barliaa
(fended Saad
Xaaohara* baa Saad
Spaa.
latalaad
Cmilatlvo latalaad Cwalatlve latalaad Cnaalatlre latalaad Cwulatlva latalaad emulative latalaad CuaulatIt * latalaad latalaad
Ballafoobaiaa
Sorfaaa Soli
Ap B Borlaoa

s i m AiAUsis. m

Clay
Mlaal - C Barliaa

cm

U.S. Bvraau of Sollt
Claeeifloatton
Oraenl

2 laah
1-1/2 laah
1 laah
3/4 laah
j/B laah
So. 4
So. 10

o

90

2

97

3

1

97
90

0

96
94

3

99*
96

1

90
75

15

93
86

0

*3

95

3

51

24

72

14

55
49

13

94
89

6

46
40

11

67
61

11

14

35

38

51

10

30

21

40

Plat Orarel

Bo. 18

99

1

91

9

90

2

100

Coaraa Sand

So. 20
So. 3$

98
92

7

80
66

25

97
94

4

99
99

Madlia land

So. 40
So. 60

90
55

37

60
20

30

93
85

9

Pina Saad

So. 140

7

40

8

20

62

Vary Pine lead

Bo. 200
So. 270

4
1

6

5
4

4
4

}

1

Silt

100

100

100

100

100

14

Clay

10

38

100
99
04
70
54

100
96
87
82
74
66
60

26

25

6.5

2.2

29.2

0.0

21

Collotda
Cniahed Materials

son

CQHTA1TS
10

18

24

34

24

40

Ion-Plaatla

lea-Plaatla

7

13

4

10

Speelflo 0rarity

2.64

2.63

2.57

2.66

2.52

2.41

loot on Ipltlen, par aaaft

4.60

5.9*

4.8$

18.52

4.$0

11.16

Orcaala Content, par aaa*

0.76

1.54

4.23

6.26

3.37

9.18

18

18

21

28

22

32

15.7

9.1

15.6

22.5

Ufuld Limit
Plaatla Iadox

Plaid Molatura Halralai*, par aaat
Shrlnlcaca Limit, par •«*
Shrlakafa Ratio

1.79

1.86

1.65

1.4?

BELLEFONTAINE

BROOKSTON

MI AMI

l.ltter.
soil.

l.ltter. leaf inn!.I
and hu m u s noil
ilH

M

l.igbt gra y ish yel
low loam.

leaf mold

D a rk bro w n ish
friab le loam.

and

hom os

gra y

r a th e r

l . l t t e r , l e a f in..Id
a n d h u m u s s. ut

Yellowish brown
friable <andv loam

Dull g ra y compact sandy rlay.
mottled with yellow a n d brown
Yellowiah brown
d a y or sandy atony
clay, relatively Im
pervious.

\
Keddish b r o w n
slightly
com pact
sa ndy loam, m ade
coherent by a small
a m o u n t »f sticky
day

if •
- >•

Sandy or stony
calcareous yellowish
g ra y rlay. usually
ex ten ds to a depth
of several feet

FOX
l.ltter, leaf mold
a n d hum us soil.

Hlulab g ra y m assive clay to
sandy clay, m ottled w ith yellow
a n d brow n. May conta in scat
tored boulders.

Ail u n c o n so lid a t­
ed m ass of sand and
gravel with o c a
sinnal layers ;in.|
pockets of sandx
clay a n d silt which
e x te n d s to a depth
of several feet.

COLOMA
Uttar, laaf mold and humus
soil.

Grayish browa sand.
Yellowish brown
friable sandy loam.

•c
Doll yellow aand, dark and
loamy la upper part.
Keddish b r o w n
sa ndy loam. Made
coherent by a small
am ou nt o f atlcky
day.

SOIL SERIES
USED <* GRASS HOT
STUDIES
INV ESTIGATION ON TURF

Stratified, calcare
oils, looae sand and
gravel exte nding' to
a depth of 10’ or
more

-)
Pale yellow aaad containing
-i pocketa of clay and coarse drift
H extends to a depth of several feet.

G R O W T H O N HIGHWAY S H O U L D E R S

TURF GROWTH.
Adequate standard methods have not been established for
measuring the quality of turfs for highway shoulders or air­
ports, but an attempt has been made during the period of the
test to estimate the percentages of grass coverage, type of
grass coverage and In general the density of the turf.

Attentioi

Is again called to the fact that no additional seeding has been
applied since the start of the test and fertilizer was applied
only three times following the initial application.
present accepted standards,

Under

from studies of the Highway Research

Board Committee on F.oadslde Development (12), a turf for high­
way shoulders is considered to be satisfactory if It is dis­
tributed fairly evenly over the ground or shoulder surface
equivalent to a sixty-five to seventy per cent coverage.

A

more dense turf covering would present a more pleasing appear­
ance, but has not necessarily proven better for shoulders or
more suitable for traffic duration tests as brought out in
previous literature (1) and in this study.

The effects of

the various soil mixtures on the growth of the grasses are
shown in Table III.
It will be noted from a study of Table III that the
Kentucky bluegrass did not survive into the second, year, in
competition with the better adapted chewing fescue and
domestic ryegrass, on any of the test plots.

- 19 -

U U III

p*c«mai or Dirmrt qsassb
ii tohp roi 1945 to 1951
I N C O H E R E N T SAND

GRAD ED S A N D

22-A

P I T RUN GR AVE L

40

98

m

100

(mi.0)

60 (> 1. 9)

P R O C E SSE D GRAVEL

The domestic ryegrass germinated very quickly in the
fall of 1944 and the early part of 1945.

The growth of the

domestic ryegrass seemed to correlate very closely with the
proportion of fine materials in the mixtures, and an excel­
lent cover wae observed on the plots containing the greater
relative amount of fines.

This was observed on the plots

containing Brooketon loam material in combination with the
22-A graded gravel material and also on Beliefontaine sandy
loam material over incoherent sand, pit-run gravel, or 89-A
graded gravel.

In each case the percentage cf fin^p, material

passing a 200 mesh sieve, was large in proportion to the other
plots in the test section.
On plots containing Brookston loam and mixtures of clay
and neat added to a graded sand base material and Chewing
fescue was the only grass to survive into the 1945 growing
season.

It was also found to be the dominant grass on all

plots over incoherent sand, nit-run gravel and 2^-A
gravel subbase materials in the 1945 test data.
ing exceptions to the above w^re noted: 1)

The follow­

Domestic ryegrass

predominated on all plots in which Bellefontalne sandy loam
was Incorporated into the top six inches of the subbase mater­
ial; and 2) on the 22-A graded gravel subbase material into
which twenty and thirty per cent Brookston loam surface soil
was Incorporated and also on the pit-run gravel material to
which thirty oer cent of the Brookston loam surface noil was
added.

This could be explained by the fines in the 22-A

- 21 -

graded gravel and the pit-run srr«v=»i In combination with
the clay from the Brooiston loam soil providing good ^ater
holding and supplying properties.
On the plots in which seventy-five to one hundred per
cent Bellefontaine sandy loam were incorporated the turf con­
tained from ten to fifty p°r cent quackgrass, and this car.
cr.ly be explained ir. the fact that the tcpsoil of this series
contained the quackgrass seed and rhizomes when it was used
as an additive.

This same observation was made on the plots

containing large proportions of L'iani toosoil and the eame
conclusions arrived at.
plantain,

For the above reasons s o o p weed,

sorrel, dock, dandelion and thi3tle seeds were also

transplanted with resulting occurrence on the plots.
weeds flourished and spread to other turf plots,

These

especially

on plots in which Bellefontaine sandy loam was incorporated
as an additive material.

As mentioned before, quackgrass

proved to be a very good turf for stability ann durability,
but being classed as a noxious weed ite use for shoulder work
or airport turf is prohibited.
During the 1945 growing season and subsequent winter al
of the domestic ryegrass disappeared from the turf after
flourishing sc rank in the fall of 1944 and spring of 1945.
The resulting turf cover on these plots v.'as very low in 1945
since the chewing fescue had been crowded by the rank growth
of the domestic ryegrass.

This observation was noted espec­

ially on plots with 22-A grai°d gravel, pit-run gravel, and

graded sand materials containing twenty to thirty per cent
Brookston loam surface soil as an additive material.
The turf on all plots except those of Incoherent sand
deteriorated during the 1945 growing season,

since there was

extremely light rainfall during the period.

The total rain­

fall from June £0, 1946 to August 1, 1945 was approximately
.05 Inches, and only .78 Inches for the month of August.
Table IV.

Chewing fescue and quackgrass arc drought resistant

becoming do m a n t during drought periods and recovering quickly
when moisture is again available.

They

recovered very well

during the fall months of 1916 when the rainfall was nearer
normal for this area, and also durinm the growing season of
1947.

During the 1947 growing season the moisture conditions

were near ideal for the growjr.j of grasses.
During the 3.947 growing season, and especially luring the
spring months,

the quackgrass flourished with the high per-

clpltation rates and good growing weather.

During this period

on the plots containing additives of illami soil, the quack­
grass made up as much as fifty per cent of the entire turf
cover with only one exception, and that was on the plot con­
sisting of a very low amount,

ten per cent, of Liami soil ad­

ditive to a 22-A graded gravel subbase.

On the plots contain­

ing Bellefontaine additive materials the per cent of quaci^grass turf was influenced by the soil mixtures,

the greater

the amount of additive material the more quackgrass turf.

-

23

-

On

m

rH

to

•

cn

CM

o

to

cn

to

•

m

•

•

co

to

9

to

00

cn

IN

00

i— i

cn

m

9

CM

CM

IN

•

0»

O

•

CO

in

RLCCRD

m

cn
i—i

rH

CO

m

RAINFALL

•

CM
•

o

o

rH

o
cn

i— t

cn

CM

CO
CO

to
D

lO

CM

•

lO
m

9

E'­

en

9

tO

to
co

CM
IN

9

cn

o

9

1—1

to
r—1

•

m

IN

m

CO

CD

i
—!

cn

9

IN

to

02

CO
rH
•

00

IN
IN

CM
in

H

rH

CM

tO

00

rH

rH

•

m

o

•

rH

CM

•

CM

CM

00
in

•

CM

CD

9

•

•

cn
•
CM

rH

CM
•
lO

to

o

rH

r— 1

rH

Cvi
rH

IN

CM

IN

tO
•

IN

to

•

rH

to
•

rH

to

•

LO

IN

10

rH

to

9

oo•

CM

iH

rH

to

't

to

to

IN

rH

9

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m

to
•

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IN
•
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■
M
1

rH

rH

CO

CM

§

to

cn

cn
cn

cn
•
o

•
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to

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rH

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to

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to

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cn

rH

cn

rH

cm

o

9

rH

i—i

m

m
rH

O

tO

00

o
CO
9
CM

to
in
•
CM

m
CM
•

in
o
•
o

to
o-

CO
c•

IN

to
00

•

ao
to
•
to

9

m
CD
•
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CM

CM

O
H1

CM
•
CM
rH

tO

CM

to
to
•
CM

o

GO
•
CO

9

in
•
CM
CM
CO
•
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•
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tO
to
•
rH

rH

•
CO

Q
•

o

rH

CM
O
•
m

CM
to

o
cn
•
CM

in
to
•
CM

•

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CM
•

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CO
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rH

lO
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CO
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CO

CO
O
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r•

cn
n
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PCM
•

cn
CM
•

rH

9

o
CO

CO
•

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cn
in
•
o

o
m

•
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to
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•
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to
n
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CM

co
IN
•
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cn

in

cn
n

H

H

•
IN
co

to
rH
•
CM

CM
CO
•
H

IN
•
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n
CO
•
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CM

to
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i— 1

to
•
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CM
n
•

o

•

9

•

H
$

9

9

H

r— I

IN
CO

IN
•
t—1

cn
•
o

CO
00
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IN
CO

to

CM
M*

in
CO

CO

9

9

9

CM

CO

1— 1

•
CM

to
o

O)
CO
•
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CD
CM
•
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in

o

9

o

CM

o
9
to
CO

Jh <U O

a

a: aJ i
>» U H
oo
O

00
c-

IN
IN

to
CM

> <n
aJ H

co

IN
IN

CM

•

CM

tO

tO

<N
CO
•
CM

tO
to
•
CM

•
CO

co
o

•
CM

CM
n
•

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CO

*
C}
oJ
t-j

•
n
a>
Ct,

•
as

u

•
a,

<L>

u

a

<

>»
rH
Ci
h>

•

aD
<

•
4-3
Or
<D
03

9

4->
a

o

•

>
O
’
-=5

9

o
03
Pi

Table IV
Summary of Precipitation on Local Watershed
- 24 -

i— 1
0}

o

Eh

the plots with only fifty per cent additive material no quackgrass was evidenced on three plots and only ten per cent on
the fourth plot.

On these plots Chewing fescue was able to

overcome the quackgrass which had a more scattered seeding and
the fescue afforded a turf coverage of from eighty-five to
ninety-five per cent in all cases.
The results of this study tend to indicate a desirable
source of the additive materials and the amounts of them to be
used as additives to reduce the possibility of quackgrass run­
ning out the sown grass species.
TURF COVERAGE
To evaluate a given highway shoulder or airstrip, the
density of turf coverage is th*= critical point in question
and not the amount or rankness of the turf growth.

The densi­

ties of the turf coverage from 1945 through 1951 on the plots
are shown in Table V.

From these data the effects can be ob­

served of varying soils, of seasonal and climate variations,
and of the gra 3 s varieties for those planted and those occur­
ring in the mixtures as vegetative additives with the surface
soils on the turf.
On the basis of the standard seventy per cent cover of
turf stated previously (12)
highways,

for shoulder turf coverage on

it will be noted from Table V that all plots con­

taining 22-A graded gravel subbase materials,
all additives and on all plots,

- 25 -

incorporating

in which thirty per cent

TABLi T
p & c i u t c o r a tA G s o r rokr
19»5 TO 1951

INCOHERENT SAND

4C

ui
c>

G R A D E D SAND

PIT

RUN GRAVEL

2 2 - A PRO CESSED GRAVEL

Miami loam, thirty per cent Brookston loam, or seventy-five
to one hundred per cent Bellefontaine sandy loam were Incor­
porated as additives, proved to produce satisfactory shoulders
in 1945, less than one year following construction and plant­
ing of the plots.

This standard is only on coverage of turf

density and is not taking into account load bearing which
will be covered later in this report.
During the 1946 season the turf on the 22-A gravel base
material was satisfactory for highway shoulder purposes, with
grass coverages ranging from sixty to ninety per cent of the
plot surfaces.

The same was found to be true on plots having

twenty or thirty per cent Miami loam surface soil as an acUditive to the subbase material,
ninety per cent coverage.

those having from sixty to

The plots having Bellefontaine

sandy loam admixtures also resulted in satisfactory turf
densities for shoulder purposes.
The turf on the plots of graded gravel,

sand or pit-run

gravel was found to be inferior to standards, or in general
not as satisfactory as that produced on the 22-A graded gravel
subbases or on the incoherent sand based plots.

The turf

densities on the plots having clay and peat additives was
found to be not as satisfactory as that on plots having loam
mixture added to the subbases.

As previously noted the plots

having a rank growth of domestic ryegrass were found to be
below the standards during the 1946 season since the ryegrass

- 27 -

died, out leaving Chewing fescue as the only cover.

This con­

dition prevailed on plots with subbases of pit-run gravel and
graded sand with Brookston loam as the additive material.
The growth of the grasses were generally improved in
1947 on all plots with the relatively high precipitation dur­
ing the spring and early summer months.

Table IV.

The turf

was found to be unsatisfactory on only six plots as noted in
Table V.

It was noted however that in all cases the turf

density was greater than for the same period in 1946.

The

plots affected by the dying out of the ryegrass had regained
density over the 1946 growing season until all plots were
only slightly below the accepted standards of coverage.

It

will be noted from the data that all plots are approaching a
maximum density in 1947 where no unforeseen events,
dying out, have impeded the progress.

such as

By referring to Table

III, page 20, it will also be noted that on the Miami soil
additives quackgrass became the dominant grass over the
Chewing fescue.

It can be observed quackgrass was not in­

creasing over the 1946 levels in any other plots regardless
of subbase or additive materials.
After the 1947 growing season the plots were maintained
in the same manner as in previous years but no further ferti­
lizer applications were made in April as before.

It will be

noted that the coverage and turf density data in Table V
bear this out and it is clearly reflected on all plots with
the exception of the Miami and Bellefontaine additive plots

_

23

-

where the turf density was not too much affected.

The plots

of clay and peat were the ones that clearly Indicated the need
of additional or supplemental seedings and fertilization con­
tinuation.

The plots on the Brookston soil decreased in turf

density but not as radically as the clay and peat.

With in­

creasing amounts of Brookston soil there was a marked variation
in density of turf on both incoherent sand and processed 22-A
graded gravel with only slight variations on the graded sand
and pit-run gravel.

In general the Incoherent sand and pro­

cessed 22-A graded gravel were better with all additives
through this portion of the test, and this was also reflected
in the plate bearing studies.
The per cent of different grasses in the various plots
showed slight variations during the period from 1948 to 1951.
It will be noted in Table III, page 20, that the per cent of
quackgrass on the i.ilami additive plots increased in all cases.
Tld-s can be explained by the gradual dying out of Chewing
fescue and replacement with quackgrass.
On the Brookston plots the turf density was fairly con­
stant with very little variation in percentages of various
grasses.

The quackgrass did not seem to spread too rapidly in

these plots on any of the subbase materials.

The same was

true for the clay and peat additive soils on all subbase
materials.
The Eellefontaine plots had very little variation in the
percentages of Chewing fescue and quackgrass, but there were

- 29 -

traces to Increasing amounts of bluegrass originating from
surrounding cover on experimental plots in the vicinity.
In general,

a satisfactory turf coverage to meet current

requirements for highway shoulders was present throughout the
test period on all plots having Miami and Bellefontaine ad­
ditives, on incoherent sand and processed 22-A graded gravel
with Brookston and clay, and peat additive soil materials.

The

plots with Brookston and clay and peat additive materials on
pit-run gravel and graded sand were, in general, below the
accepted standards of from sixty-five to seventy per cent
coverage.
Root penetration measurements were made as shown in
Figure 3.

It will be observed the root density which was

taken as representative or an average of all plots.
stability

of

turf

plots

One year following the construction of the turf plots
and the fall seeding, two types of stability tests were con­
ducted on the plots to determine and evaluate their ability
to support stationary and moving loads under conditions of
saturation as well as when dry.

The first of the series of

tests consisted of applying a static load through a one
hundred square inch bearing plate and measuring the amount of
penetration at various load increments.

A round bearing plate

was employed which is considered general practice (6).

- 30 -

Firure ?
Vif-v shoving on '.vt-v; :e root or-notroi L:>n
<
•r.-J root. -.entity.

The second, series of tests were made to check the re­
sistance of the grass turf to rutting.

This was accompli shed

b y d r i v i n g a h e av y truck o v e r the pl ots and meas ur in g the var­
ious depth s of resulting ruts caused by the movi n g wheels.
w h e e l loads on the rutting test were single tire type.

The

The

p l at e b e a r i n g tests were all conducted on the soil in its nor­
mal environ me n ts as to p e r cent moisture while the rutting
tests were c o n d uc te d on sa turated plots
spring breakup

conditions,

to simulate early

and other rutting tests were car­

ried out on d r y or low moisture

contents which woulo

compare

to summer conditions.
The series of rutting tests were carried out only once
during

the 1945 season,

but the plate b e a r i n g studies were

co n t i n u e d during the years 1947,

1949,

1950 and 1951 at ap­

p r o x i m a t e l y the same season to obtain comparable conditions
on plots.
P L A T E BEARING- TESTS
A

truck w i t h a gross weig ht of ap p roximately twelve

tons was used for run ni ng the plate b e a r in g studies.

The

truck was carefully backed Into pos it i on w it h the rear of
the frame o v e r the selected
and 5).

The one hundred

area to be tested.

( figures 4

square Inch pla te was p l a ce d on

the turf surface a n d worked down slightly by hand to in­
sure it was in a level position.
a dial

A frame was employed for

support for me asuring the plate

- 31 -

settlements under

load.

This frame w a s supported cn the g r o u n d a distance of

at least

four diameters of the plate away from the l o a d e d

p l at e and free cf the truck w h ee ls o r frame.

The frame

sun-

p o r t e d a one t ho usands dial w i t h the stem resting in the
center of the b e a ri ng plate.

The l o a d was tra ns m it te d

to the plate through a clotted cylinder v/hich w a s p l a c e d ever
the d i a l and a d j u s t e d to c e n t er on the b e a r in g plate so the
dial face could be read thro ug h the o p e n i n g provided.
this

slotted

draulic

Jack.

c y l i n d e r a plate was p l a c e d to
To the hydraulic

C ve r

support the hy­

Jack there was a t t ac he d a

cal ib ra te d d y n a m o m e t e r ring with the u p p e r fitting of this
ring resting against cribbing cn the track frame.
assembly^

loads up to 7,000 p o un d s were applied

W i t h this

to th<= turf

surface of the plots with a resulting nre ss u re of seventy
p e r square inch m a x i m u m on the plots.
sufficient

to p r o d u c e the r e s u l t i n g p late

quired in these studies.
of the ap pa ra t us can be
A

This load w t.n

settlements re­

Ar. over-all view and a general view
seen in Fig ur es

i and 5.

small p r e l i m i n a r y load was a p p l i e d to seat the plate1,

after w h i c h the pl ate was l o a d e d fully.

The l o a d was applied

in five h u n d r e d p o u n d increments in a sequence de t er mi ne d by
the rate of settlement of the plate and this of a n e c es si ty
var ie d the l o a d i n g period from one plot to another.

Wh e n

Che

settlement dial i nd icated no

further settlement the next in­

crement of load wa s apolled.

These Increments v;pre repented

until

the limit of th*=> dial travel had been reached cr r, load

of 7,000 pounds had

been aprlied.

-

32

-

'WMMfllllM,/

F r o m the b e a r i n g p l at e
e a c h test

tests graphs w e re constructed

to i n d i c a t e ratio of settlement

in the A p p e n d i x c o n t a i n s r ep re s e n t a t i v e
graphs

to load.

for

T a bl e I

examples of these

s h o w i n g curves for t-uccessive years tests to illustrate

c o m p a r i s o n s as the turf g r ow th pr o g r e s s e d and r e s ul ti ng be a r ­
i n g v a l u e s Increased.
plots

turf

there we r e a c c o m p l i s h e d d e t e r m i n a t i o n s of the subgrade

modulus
lated

" k H for a 2500 pound

in Table VI.

plots,
When

F o r c omparative results of the

and density

l oad and the results are

tabu­

The m o i s t u r e contents of the respective
d et e rm in at io ns are included in Ta ble VII.

the plate b e a r i n g tests w er e car ri ed cut, m o i s t u r e and

d e n s i t y d e t e r m i n a t i o n s w e re also
w e r e c a r r i e d o u t in 1947,

1949,

taken.
1950,

The series of

tests

and 1951 and the re­

sults a n d c o r r e l a t i o n s for each y e a r are I ncluded in Table
VI

as a c o m p a r a t i v e

a comparative

table of subgrade values.

s t a b i l i t y gr aph

F i g ur e 6 is

for the plots.

T e s t s d u r i n g 1950 and 1951 were cor re la t ed to p e n e t r o ­
meter

studies w i t h a r e s u l t i n g study w h i c h is included later

in this re po r t as c o r r e l a t i o n s w i t h com pa r ab le results.
RUTTING- T E S T S
A

second

series of stability tests o n the turf plo ts

were c o n d u c t e d as rutt in g tests wltn a l o a d e d truck,
a xles and four wheels,
w h ee l

two

o v e r each plot a n d no ti n g the d e pt h of

rut.

- 34 -

TABLE VI
S ubgrade Llodulus "k" for 2500 P o un d L o a d
Plot
No.

1947
Pe ne tr a- "k"
tlon*

1949
Pene tr a- "k"
tion*

19 50
P e n e t r a - ’'k1*
tlon*

19 61**
P c n e t r a - "k"
tion*

1

0. 54

46

0. 22

110

0.19

139

0. 23

109

2

0.49

51

0.22

106

0.17

147

0.20

125

3

0.80

31

0.17

187

0 .14

170

0 .14

178

4

0. 64

39

0.32

76

0. 2.7

91

0. 29

87

5

0.35

75

0. 24

108

0. 25

101

0. 23

107

6

0 . 43

57

0. 33

70

0.2.5

99

0. 28

90

7

0. 52

48

0. 30

83

0. 29

00

0. 27

93

8

0. 44

57

0.41

63

0. 44

60

0. 39

64

9

0. 23

109

0.36

66

0. 35

70

0. 33

76

10

0. 48

52

0. 20

121

0. 29

91

0. 18

139

11

0. 51

41

0. 18

133

0.32

79

0.19

131

12

0. 90

28

0.13

139

0. 33

77

0. 20

125

13

0. 24

104

0.21

110

0. 29

93

0 .1 8

139

14

0.25

100

0.2.2

108

0. 28

97

0. 19

131

15

0. 24

106

0. 21

122

0. 25

101

0.18

139

15

0. 44

57

0.22

111

0. 2a

96

0. £2

113

17

0.33

77

0. 31

78

0.35

70

0.32

78

18

0.35

71

0.35

70

0. 35

71

0.34

74

19

0.30

66

0. 34

75

0.36

69

0.18

139

20

0. 57

44

0.21

116

0. 33

77

0.27

93

21

0. 48

52

0. 30

85

0. 35

67

0.18

139

22

0. 35

71

0. 20

128

0. 29

91

C. 18

139

* P e n e t r a t i o n In Inches
**
1951 D a t a from P e n e t r o m e t e r curves

T A BLE VI
Plot
No.
23

1C 47
P enetra- itfcii
tion*
0. 43

58

24

(Cont'd)

1949 i
P enetra- iikii
t Ion*

19 50
P e n e t r a - "k"
tlon*

1951**
P e n e t r a - Hk»
11 on*

0. 23

100

0. 28

97

0. 20

125

0.09

265

0.12

2.01

0. 11

221

25

0.20

125

G. 07

567

0.16

151

0.17

149

26

0 .15

164

0.18

130

0. 13

172

0. 15

167

27

0.10

236

0 .14

176

0.12

191

0.13

192

28

0.16

158

0.17

144

0. 30

83

0. 21

119

29

0. 19

135

0.23

112

0.25

99

0. 14

176

30

0.17

150

0.13

171

0. 22

107

0.12

206

31

0. 20

12 2

0.13

235

0.16

147

0 .1 2

206

32

0. 50

50

0. 20

125

0. 28

98

0.18

139

33

0. 58

43

0.18

137

0. 28

97

0.19

131

34

0. 58

43

0.09

256

0. 29

92

0.13

192

35

0. 39

64

0.13

208

0. 29

91

0. 13

192

36

0. 67

37

0.18

145

0.35

72

0. 15

167

37

0.09

28 7

0.09

275

0. 09

290

0.09

279

38

0.11

22 7

0.08

294

0.09

282.

0.10

250

39

0.14

179

0.09

29 5

0. 10

2.’71

0.09

279

40

0. 19

130

0.09

0. 10

270

0. 10

250

41

0. 16

154

0.0 5

390

0.09

281

0.09

279

42

0. 25

100

0.13

188

0. 14

175

0. 13

192

43

0.16

156

0. 11

r

0. 12

194

0.13

192

44

0. 59

42

0.06

465

0. 11

206

0. 11

221

45

0. 52

48

0. 27

93

0 .13

177

0. 21

119

46

0.36

69

0. 05

510

0. 28

95

0. 26

96

47

0. 22

114

0.06

415

0. 26

109

0. 20

125

48

0. 55

46

0.08

50 5

C. 28

97

0. 27

93

EIJ3ITY
P lo t
No.

19^7
P ercen t
Deni..ols-*tt city*
t ar e

atr ^

X
.*ClSTIJhD DATA

19 49
;Perc°n t
Dfcii1. di pc—
f 11j
tu rn

Fe-rcen t
.... ’1 et are
t *«<
^0

1

10.01

10. 4

90

o

10.01

b. 7

b6

11.2

5

10. 01

15. 0

95

1o • 5

4

10.01

9 .2

101

lo . 1

b

10,01

' > ’•v

bl

5

10.01

o.3

7

10. 01

8

13 50
De:ip lty

bl

19 bl
F e :c en t
Den.
Del sF it
t are
12.

c?e

12. 6

101

r o • le

■
*i■
'n
C
b

97

12. 1

39

9 .1

91

10 . 2

30

94

10. 2

30

9.3

96

o. 4

37

10 . 2

96

10 . 5

93

10.01

b. C

yo

10.3

92

19.0

3.7

9

10. 01

o• o

90

10 .1

90

9 .7

rt 9

10

10. 22

5. 3

96

I:- . 1

9b

11. 4

97

11

10 . 22

b. 6

bb

12.4

b7

12.4

69

12

10. . 2

b. 4

97

12.1

100

12.0

101

13

7.33

4. 0

101

12.0

100

11. 7

101

4. u

101

10.9

lb . 3

101

101

b. 1

100

O• )

102

4. 6

101

b. b

102

97

■±. 7

39

S3
o
3
n>
C
D
£
o
c

100

14

? . ij 9

15

7. 39

3.

16

7. 3b

4.0

101

17

7.3b

4 .1

yd

id

f . 33

•±.0

37

• *J

99

b. 3

101

19

7. 33

97

6 .1

100

6.1

100

20

7. 39

0*0

100

b. b

10 J

O•

101

21

7. 39

ec. v.)

9b

7 .1

-2O

22

11.16

b. 3

9b

b. 1

10' 0

23

11.16

b. 3

91

3.0

bO

*0 er e11j

unitf

ar e

o. f .

b

4

.5

100

3b

7 .1
• c./

bl

3 .1

i r t a r e a n i t e _)e r • *- n

100

>
«I •v

• •

’

TA B L ‘D VII (ContT.)
Plot
No
.

19 47
Percent
Lensit/
t u re

19 40
Percent
Leni..o1 v?r 1tj
ture

24

11.16

25

2. 67

•

122

2.6

2. 67

3. 0

27

2. 57

28

Id 50
Den­
:.aO3.ssity
t ure

F e r e n it

le 31
F e r e *n t 0 o n •
*..oi e^'1 t;
tu re

d7

4 3

'•

3.20

O .'.J

121

120

G .D

122

7.4

1 24

3. 2

119

7.4

123

7 .- x

120

2. 57

5. 0

120

6.7

121

e.l

122

29

2. 67

3.1

116

lo. 5

120

10. 6

119

30

2. 67

2. 6

117

10.1

117

10. 1

117

31

2. 67

115

«. 7

117

10 . 1

117

32

4. 65

3.3

112

*^

113

6 a1

110

33

4 . 6b

3. 4

115

5. 7

117

j . x)

117

2.0

116

7.2

115

7.9

115

3. 7

101

7.0

100

7. 6

101

4. 0

dl

7.1

90

7.4

91

3. 0

116

7. 7

11 o

7. 6

116

2. 6

110

5.1

110

7.4

111

5. 4

^

97

'. 7

j

7

CD

34

4. 66

35

4. 6B

36

4. Ob

37
38

cj

4. 11

<D
£
O

**•1 1

rt

oS

4. 11

.0

109

7. 5

109

7. 5

110

*0

4.11

2.6

112

7. 1

114

’?

1

113

41

4 .11

5.0

11-*

6. 7

114

6.6

114

42

4. 11

o •4
o

10 6

6. 1

10 5

■w'9

lu 5

'±3

4. 11

L: 5

113

6. 4

117

4:4:

C abO

4

114

7 o

45

6. 26

o

. .

3.06

5

-±6

o 2u

3. 2

10b

7. 7

47

6. 26

w r~-i

•- •

* 0

4-5

6. r.6

4. 5

52

‘
J . 3.

.

a

.

a

'

«_>

-.

A_
oo-a

.

a.

•

’)

116

lit

1

11 4

107

7. r

1J7

107

7. 1

1 7

•-+ 1

d6

1

1 jJ

•

J

a

192

STIFFNESS

MODULUS

"K

RC.I.

PROCESSED
GRAVEL (22A);

PIT RUN GRAVEL

GRADED S A N D o .-b

DUNE SAND

PLOTS IN ORDER OF INCREASING STABILITY

STABILITY RELATIONSHIP
POTTR POTT R A F F Mf l TFRTf l T F

The load e m p l o y e d was 10,000 p o u n d s on a r e a r axle sup­
p o r t e d o n two 1 0 . 0 0 — 20 tires w i t h a tire p r e s s u r e of
p o u n d s p e r square
to p r e v e n t

Inch.

The t r uc k wa s d r i v e n In c r e e p e r gear,

s t a l l i n g in the m or e u n s t ab l e

s e c t io ns w i t h low Inherent
a n d 8.

seventy

sections.

Typi ca l

s t a b i l i t y are shown in F i g u r e s 7

C o n s i d e r a b l e d i f f i c u l t y was e n c o u n t e r e d in rutting

stu di e s and it w a s felt their value d i d not w a r r a n t f u rt he r
studies

in suc ce ss iv e years.

T he effects of the p a s s a g e of the t r u c k w a s m e a s u r e d by
the em pl oy m en t of p r o f i l e s of the plots.
r e f e r en c e

P r i o r to the testing,

stakes w e r e driv en on each side of the p lo t at a

p o s i t i o n w h i c h w as well o u t s i d e

the zone of influence.

Follow­

ing the r utting a straight edge was p l a c e d across

tnese re­

ference

straight

edge

stakes a n d v e r t i c a l m e a s u r e m e n t s

to the turf were made at

plots.

from the

six inch int er va ls acro ss the

'.71th this pro ce du re p r o f i l e s in the v;et a n d dry state

were m a d e p r i o r
d a t a for

to the r u t ti ng and i m m e d i a t e l y following.

the r u t t i n g tests Is p r e s e n t e d in Table VIII.

is a c o m p a ra ti ve b a r g r a p h f o r the r u t ti ng a n d b e a r in g

The

Figure 9
studies

c o n d u c t e d in the 1947 studies.
P E N E T R O M E T E R TESTS.
F o l l o w i n g three years of stability tests the p e n e t r o m e t e r
s tudies w er e a t t e m p t e d on the turf pl ots to

show some close cor­

r e l a t i o n o f such studies w it h p r e v i o u s l y c o n d u c t e d pl ate bear­
ing tests.

-

38

-

4

r

£
j

X

ji. a

X

"13 I \

t. ’

^i .. „. ^ Ca

■:%rc

-j

/ .
vj iV

v

_ i I'1 j

. . i_

V

_x_

.i_ i i

•>

i. i *,i i *. / ^r i v>

L

-

' " .. A

' • i. -

!.

L;j

, -i-1 .i i

'.j ^y

t

u

'•

TABLE VIII
R E S I S T A N C E OF TURN TO R U T T I N G
Loa

} lbe.

per wheel (10,000 lbe.

Pic
No.

t Depth
•. C dry)

"h"

Percent
Lole, ture
( dry)

on rear axle 2 wheels)

Rut Depth
In. (wet)

"L"

P ercent
hoIsture
( wet)

1

3. 5

20

1.9

57

2

2. 6

27

2.8

25

3

1.3

54

3.1

23

4

1.9

37

4.0

17

5

1.4

50

3. 2

22

6

1.1

64

2. 2

32

7

2.4

29

3.0

21

8

2. 7

26

3.4

21

9

1.6

44

2.5

23

10

1. 6

44

3. 2

22

11

0.4

175

2.4

29

12

0. 8

87

5.0

14

18.1

13

5.3

13

2.4

29

7.8

14

3.

4

21

2.8

25

15

2.0

35

2.7

26

16

3.

4

21

3.6

194-

17

3.9

18

4. 2

17

18

2.0

33

2. 3

30

19

3.0

20

2.9

24

20

2. -j

32

2.9

24

21

1.9

37

2. 5

28

22

0. 5

140

3. 3

21

3. 83

5. 53

- 40 -

8. 7

20. 6

11.1

T A BLE VIII
Plot
No.

Rut Depth
In. (dry)

"k"

(Cont'd)

P ercent
Lloi s ture
( dry)

P ercent
LIol s ture
( wet)

Rut Depth
In. (wet)

23

0.6

117

1.2

58

24

0.3

233

4.2

17-

25

2.6

25

2.6

25

26

2.0

35

2. 3

25

27

1.4

50

2.2.

32

26

2.3

30

2.4

29

29

1.4

50

2.0

35

30

0.3

233

2.0

35

31

1.2

56

2.0

35

32

1.8

39

2.9

24

35

0.3

233

3.0

23

34

0.3

233

2. 2

32

35

0.4

175

2.0

35

36

0.4

175

2.8

26

37

0.5

140

3. 6

19+

36

0.1

700

3.4

21-

39

0.0

00

2.8

25

40

1.0

70

2.9

24

41

0.4

175

2.9

24

42

0.7

100

3. 0

23

43

0.4

175

2.9

24

44

1.1

04

3. 2

22

45

0.2

350

2.1

33

46

0.3

233

2.0

35

47

0,4

175

2. 2

32

48

0.2

350

3. 9

18+

2. 67

4.11

- 40—A

17.7
5.8

8.1

19.1
7.2

17. 7

D_
D
*a 100
8•k
a

INCOHERENT SAND

CRADCO

5ANO

PIT RUN GRAVEL

PROCESSED

G R A V E L -2i

Z

RUTTING UNDER 5 0 0 0
POUND
WHEEL LOAD
1 0 . 0 0 - 7 0 T I R E A T 7 0 P. S. I A I R P R E S S U R E
SO IL SATURATED

x
o
z
I

I

*

o
I 7 A B 7 S I 0 3 2 0 I I 6

U
k

l

l7 27w 22l9»IA I52ilT i32T

33 37 75 26 36 2 8 * 7 3 aW 30 4r 35

300

a

200

IOO
U
2J
u
u..

Ru

tt in g

under

10.00-20

sooo

po u n d

TIRE AT 7 0 P S I AIR
S O I L DRY

w h eel

load

PRESSURE

a

o

u

I

»-

fcj

a

21 2322 24

25 26 26 32 2 7 29Y

u

a.
*

200

?

IOO

bl

PENETRATION
UNDER
BEARING
A R E A I OO S O . I N
S O I L ORY

PLATE

ui

X
o
z
z

o

0.5

><

ac

►
ui
z
a

rm

UJ

36 34 33 32 35 31 25 29 30 26 26 27

UMBER

*© E

TEST

ARE*

4 4 4 6 4 5 4 6 4 2 4 7 40 4 1 4 ^ 3 9 3

The p e n e t r o m e t e r has b een used, for a numb e r of years
m ore or lees successfully
ity,

for field checks of density,

a n d tilth studies in the

o b j e c t i o n s to its u se were the
p e n e t r a t i o n rate,

field of agriculture.
small b e a r i n g area,

stabil­

The main
non-uniform

the p o s s i b i l i t i e s of ob t a i n i n g erroneous

resul ts caused by striking
h e a d s on the b e a r i n g area.

stones,

or the formation of pseudo­

It is not p o s s i b l e to change the

bea ring area since only the operators weight is employed
effecting penetration.

E l i m i n a t i n g p s e u d o-heads or the chance

of striking objects is also
ate.

for

impossible to correct or elimin­

The u n i f o r m pen e t r a t i o n problem can however be accomplish­

ed by employment of the "Hanberton"
Instrument

(13) penetro iiie t e ]T.

Th 1s

shown in Figures 10 and 11 employs a system whereby

eac h p e n e t r a t i o n is recorded on a graph as shown in Figure 12.
The graph Is a trace of the resultant p r e ssur e required to
force the probe into the soil,
the probe.

and the d e p t h of penetration of

The a b c l s s a is d r a w n by the pressure of the soil

transmitted to a calibrate d coil

spring a nd the ordinate is

p r o d u c e d by the differential b e t ween the probe head a n d the
float rod foot w h ic h rests on the soil

surface.

There are

two p u l l e y systems which p r o duce the d e s i r e d four inch graph
and w h i c h compensate

for the compression of the resistance

spring.
The accomplishment of a load bearing test requires
siderable laborious and tedious \.ork, w i t h cumbersome

con­

equipment

“ i-

Figure 12.

Empirical graphs irora the Henberton
P enetroivieter

-

U5

-

1

nd considerable expense.

It m ay be possible that the use of

he penetrome ter can provide an economical,

convenient,

and

ccurate method of obtaining load bearing data to supplement
ests on constructed structure? of known soil materials.
The

soil penetrometer as used in tilth studies had two

leads, one a tapered point probe and the other a flat head with
i circular cross sectional area of 0.15 square inches.

Ad-

Litlonal heads were adapted to the equipment in various cir­
cular areas up to one

square inch.

A loca tion was chosen large enough to accommodate the
searing area and the float rod foot.

This area was cleared

3f all loose surface material such as stones and leaves in
order to provide a firm smooth plane for making the obser­
vation.
soil.

Special

care was taken to not disturb the turf or

llanual pressure was appliec

to the penetror.eter in

such mann er to produce, within reason and
gauges,

a slow,

penetration.

without benefit of

uniformly Increasing pressure and resulting

V/ith this precaution the possibility of impact

load was p r a c t ically eliminated.

The trace,

resultant of

this pressure p r o d u c e d in the coilsprlng and the depth of
penetration produced

by the differential between the float

rod foot and the probe head, was recorded automatically on
the blank chart for the instrument.
tempts were made

In taking the d a t a at­

to obtain at least three curves,

from which

composite data curves were produced for each plot.

— 46 —

4

A p r e l i m i n a r y Investigation was carried out to determine
which load would be best adapted for the specific base mater­
ials.

Theoretically the larger the head,

the closer will be

the trial curves to one another, and the erratic nature of the
curves will be eliminated.
however,

The size of head is controlled,

by the operators weight,

and that size W h ich allowed

penetrations of three or four inches.

The sizes determined

were employed in the tests and the resulting average data for
each plot, Table II, Appendix;

was compiled.

Ikloisture content and density determinations were carried
out d u r i n g the tests and are Included in Table VII

for cor­

relation to the penet rometer studies.
From the d a t a taken it was found that the tapered probe
was greatly influenced by local conditions and was,
not used in these
head

studies.

therefore,

W i t h the smaller 0.15 square inch

the penetration was excessive and the probe acted

to the tapered point and it was

similar

therefore impossible to obtain

comparable results in this work.

O t h e r sizes were

tried and

resulting experience and data favored the 0.50 square inch
and 0. 75 square inch bearing area.

In the final studies the

0.75 square Inch head was employed on sand subbase materials
and a bearing area of 0.50 square Inches on gravelly subbase
materials.

The penetrometer method was not looked upon with

too much favor for use on gravel base materials cue to the
wide ranges of hetrogenelty encountered with resulting eccentr­
icities in curve data.

Resulting pseud o— heac>.s of unknown

m a g n i t u d e w o u l d result from the b e a r i n g

surface

striking

stones o r e t h e r foreign material.
The formula for the m o d u l u s of subgrade
as e m p l o y e d in the plate b e a r i n g tests,

Where;

lr =

P
Ta T T z T

k -

Llodulus of subgrade

P =

L o a d in p oun d s

A

=

B e a r i n g are a in

stiffness

Mk M ,

is:

stiffness

in #/cu.

in.

square inches

Z = P e n e t r a t i o n in inches of b e a ri ng area.
Since the p e n e t r o m e t e r is being c o n s id ered a supplement,
r a t h e r than a supplanter of con v e n t i o n a l load b e a r i n g capacity
studies,

it w a s a s s u m e d that

only one variable, P,

be

for and in turn to solve for "k" with that variable,

solved
u s in g

the loa d b e a r i n g plate area a n d some p r e l c t e r m l n e d value of
penetration.
c o n form

In this w a y the d e t e r m i n e d values of ••k" would

to e x i s t i n g bearing plate values of Hk H .

The b e a ring

p l a t e a r e a was constant at one h u n d r e d square inches,

and a

value cf p e n e t r a t i o n of O.P.O inches v'r.s decided on for the
plate bearing studies.

The o nly v a r i a b l e

"PH could then be

o b t a i n e d from the p e n e t r o m e t e r curves.
The ability o f various base m a t e r i a l s and a d m i x t u r e s tc
support plant life and the

turf material d e n s i t y in d e pt h are

r e f l e c t e d in the first p o r t i o n of the p e n e t r o m e t e r graphs.
The limits of the root z.one as the p r o b e pe netrates it are

e v i dent in Figure 11, by the

shape of the curve.

It becomes evident then w h y the observations must be
taten duri n g the same periods of the year for any correlation,
i.e.

when the roots are growing and not in a dormant state.
The follo wing Is the method of comparison developed for

p l a t e b e ari ng v alu e s and the pene t r o m e t e r studies.
The equation;

P = L o a d in p o unds from load bearing studies with
a pen e t r a t i o n of 0.20 inches.
P 0 - L oad in pounds from p e n e t r o m e t e r studies for
a pe n e t r a t i o n of 2.0 inches.
m = Constant, w h i c h whe n m u l t iolied by P Q will give
a comparable load P for the solution of the
subgrade m o d u l u s equation.
The arithmetic mean was used for the d e t e r m ination from
the composite data in Table II, Appendix.
To illustrate

the method the following example

is given

empD-oylng the d a t a of plot 1.
P - Loa d at 0.20 inches - 2250 pounds - Load bearing data
Table V, Appendix.
Po
P0

151

If this value were now employed on any pen etrometer
value at 2.00 Inches penetration

for plot 1*, theoretically

we would, obtain a comparable value for "P"
lng data.

This Is not h o w e v e r true 3in~e

the lo^f v,por_
ve ha,re machine and

equipment

errors in both plate bearing and pene t r o m e t e r

studies.

When the values of PQ are multiplied by "LI" we v/311

only m a g n i f y the errors.

In the Illustrated case a twenty

p o u n d e r r o r in p e n e t r o m e t e r studies,
occur,

w h i c h could conceivably

would result In a p p r o xim ately a three hundred and

fifty p o u n d e r ror in load b e a r i n g determinations.
A method

conceived for reducing the Induced error was

that of employing common logarithmic values.

In this way any

small original errors can be pr a c t i c a l l y eliminated,

when con­

verted to logari thmic values.
A s before P Q is computed
Inches p e n e t r a t i o n and set up

from the composite dat a at 2.0
in the logarithmic

form.

factor "lil" Is then found and "P" det srmint'd as follows !

The
— ata

from P lot 1 1 - two trials.
p

= 157 pounds

P n ' = 146 pounds - a difference of
11 lbs.

- 2700 p o unds

L: - 17.2

°
P

1st. p e n e t r o m e t e r trial.
P = 1 7.2 (157) = 2700 pounds

- 50 -

2nd p e n e t r o m e t e r trial.
P — 17.2 (146)
It can be

= 2520 pounds

seen the eleven pound e r r o r was m a g n i f i e d to

one h u n d r e d and e i g h t y pound difference on the s&me plot.
By u s i n g common logarithmic values with the same con­
ditions:
M =

P
Log P Q

- 1230

E r r o r = 11 pounds

L o g 157 = 2 . 195

PQ

=

157 pounds

PQ i

=

146 pound s

L o g 146 = 2.164

P = (Log P 0 )L

P = 1230

P = 1230 (2.195)

=

(2.164)

= 2670 p o u nds

2700 pounds

The eleven p o u n d error has thus b een m a i n tain ed
second place

to the left of the decimal and the final

are n o t m a g n i f i e d as before
o nly thirty pounds.

Only

figures

with a r e s u l t i n g difference of

Tentatively,

employed with the determined
IX.

to the

a logari tiunlc system was

factors

of ,ti._M as shown in Table

p l ot s o f sandy subbase materi als are

included

since

those w i t h g r a v e l l y bases require f u rther investigation and
c o r r e l a t i o n w h i c h are covered l a t e r in the report.
G R A P H I C A L CORRELATIONS.
U s i n g the same p e n e t r o m e t e r d a t a as
cussion,

in the p r e vious dis­

ah attempt was made to correlate tne data in graphical

form and thus

slmplfy the computations for values of "p** on

R>1
O'*

_

i

TABLE

IX

L o g a r i t h m i c f a c t o r s ••LI** for d e t e r m i n i n g loa d »'PM

Plot
Tentative
Plot
Tentative
No._____________ “t"____________________ No.______ __________
1

1070

13

1070

2

1055

14

1010

3

1500

15

1175

4

760

16

1110

5

1180

17

87 5

6

675

18

720

7

9 65

19

9 30

8

670

20

1180

9

690

21

850

10

1 145

22

1210

11

1230

23

865

12

10 50

24

8235

-

52

-

l o a d b e a r i n g test dat a which are used ultimately for d e te r­
m i n ation of the subgrade modulus " k " .
The d a t a of unit load versus the ratio of settlement to
d i a m e t e r of c i r cular bearing area, p l o t t e d on logarithmic
scale,

results in a straight line function which is independent

of the plate

size (£2).

In this method of plotting the d at a

is gen e r a l i z e d and supposedly makes it possible to predict
settlements of any size area.
14,

15,

The curves shown in Figures 13,

and 16 indicate typical curves for load bearing test

data combined w i t h the p e n e t r o m e t e r data.

The left portion

o f the curve w a s d e r i v e d from plate bearing data and the right
por tion from p e n e t r o m e t e r data.

From these curves it is pos­

sible to take o f f values of unit load for various bearing sur­
faces at a given p e n e t r ation and thus obtain a total load
value to determine the subgrade modulus.
The above analysis is very simil C.IP in nature t;o the pre­
viously p r e s e n t e d study for the determination of the factor
.

The product

of «1.1»• and the logarithmic value of the

p e n e t r o m e t e r l oad in pounds p e r square inch determines

the

value of total load " P 11, for the subgrade modulus determin­
ations.
The d a t a d r a w n upon for the comparison covers a two year
p e r i o d and. 'would not be all conclusive,

but it does,

however,

prove the p o s s i biliti es and value for a simplified and quick
m e a n s of ver i f i c a t i o n or determinatio n of load bearing data
w i t h a recording type penetrometer.

/

1000

13, 14,15
16/ 171 18
19/ 20/ 21
22,23.24

LOAD

100

o '/'
0.01

0.1

1.0

RATIO S E T T L E M E N T TO D I AME TE R AREA

1000
2 5 ,2 6 , 2 7

2 6 ,29/30
31,32,33

LOAD

— P. S.I

34 /35/36

10//
001

o.l

1.0

RATIO S E T T L E M E N T TO D I AM E T E R AREA

10

10 0

load

— p.s.f.
o
o

N.

\\

v

i'. '

f

•£ $ “

i
£
•

**•i
*u 5
<*
<
;»

An

example

taken from the graph for plot 11, Figure 13,

the same plot u sed for the previous

examples with logarithmic

c o m p u tations w ould be as follows:
Ratio of settlement to diameter of bearing area for a
plate of one h u n d r e d square Inch cross section.
Settlement
dlam. plate

_

0 .2
11.28

_
”

q-, n 7

Referring; to the graph 0.0177 = 27 pounds per square
inch, or 2700 pounds for the bearing area used.
P = 2700 pounds.
Ratio

of settlement to d i a m e t e r o f bearing area for

p e n e t r o m e t e r of 0.75 square inches.
Settlement
a
2.0 2.05
diarn. pen e t r o m e t e r
0.977
Referring to the graph 2.05 = 160 pounds pe r square inch
w h i c h was the value r e c o r d e d in the d a t a as an average
value for plot 11 in the test sections.
Thus from the curve of K n o w n

shape and characteristics

it is possible to take a va lue of "P"
determinations.

for further modulus

These curves must however,

be b a sed on re­

p r e s e ntative plate bearing data for close correlations.

CONCLUSIONS
The C h e w i n g fescue turf which Is tolerant to low organic
m a t t e r soil c o n d ition s p r o v e d to be an excellent grass to
p l a n t on sandy and gravelly
suitable

shoulder materials where and when

stabilizing soils are available and added.

It did

not propagate vege t a t l v e l y too rapidly w h i c h is brought out
In the turf c o v er data,
yearly.

thus n ot p r o v id ing increasing cover

The c o s i r e d grass should h o w e v e r be planted alone to

eliminate c o m p etition from nurse- grasses and larger a p pli­
cations of f e r t i l i z e r made more frequently to make up for the
lack of organisms and plant food In the raw subsoil materials.
Ldiami loam,

Br o o k s t o n loam, mixtures of clay and peat,

and B e l l e f o n t a l n e

sandy loam were all found to be satisfactory

as additives w i t h sandy or gravelly base materials

for the pro­

ducti on of turf.

sandy loam

The Llami loam and Bellefontalne

also p r o d u c e d a very dense and stable turf as a result of the
quackgrass Introduced with them.
p r o v e d these p l ots

The load bearing tests

to have the highest Inherent

stability and

this may be a t t r i b u t e d to the network of roots from the quack*grass.
Subsoil

clay and peat added to subbase materials will

furnish the needed bin der and organic m a t t e r to produce a
good turf on all subbase m aterials except washed sand.

_

59

-

B r o o kston loam soil was found to be satisfactory material
o r m i x i n g with the various granular m aterials for the growth
f turf.
The d o m e s t i c ryegrass produced excellent cover for one or
;wo years and then died out leaving the fescue sparse and unible to provide

sufficient cover.

No apparent advantage was

gained by including ryegrass in the seeding mixture designed
;o produce a dense

sod.

The competitive nature of this grass

vas such that its presence

in the seed mixture resulted in a

bunchy type turf of the Chewi ng fescue.

This would lead

the assumption that the entire cover could,
been C h e wing fescue.

A

to

and should have

solution would be the elimination of

the R u r s e - g r a e s entirely or provide a supplemental

seeding of

the C h e w i n g fescue until the desired turf density was attained.
Where

small percentages of fines were prevalent in the

soils the effect of the nurse-grass dying out was not as mark—
ed as in those having a l a r g e r p erc entage of fines.

On the

l o w percenta ge plots the ryegrass blended w ith the Chewing
fescue to produce a good cover the first year with no detri­
m e n t a l effects the following years as the ryegrass d ied out.
The materials on which this w as noted were the 22—A graded
gravel materials.
Ken tucky b luegrass did not survive under the conditions
of the experiment on any of the turf plots.
I n v e s t igations of root penetration depths were
be about five Inches.

found to

This w o uld indicate that on tne average

the roots were

contained in the zone of the profile contain­

ing the additive

soil materials and not down into the base

coarse layers.
The 22-A graded gravel material
ing a satisf actory turf, w a s

in addition to produc­

found to exhibit greater stab­

ility than the o t her granular materials.
Bellefontalne

sandy loam,

fifty and seventy per cent

m i x t u r e s p r o duced high stability with incoherent sand,
sand,

a n d p i t -run gravel.

graded

The turf was found to be satis­

factory on all of these plots.
The incoherent
Brook ston loam;

sand w i t h twenty and thirty per cent

the graded sand with twenty and thirty per

cent Lilaml loam;

the pit-run gravel w i t h thirty p e r cent

B r o o k s t o n loam a n d w i t h mixtures of twenty-five per cent
clay and fifteen per cent peat;

the 22-A graded gravel v.lth

fifteen and twenty-five per cent Li1 ami loam,
B r o o k s t o n loam,

fifteen p er cent

a n d mixtures of ten per cent clay and five

p e r cent peat all produced turf of good

stability and coverage.

D e n s i t y studies on the plots ind icated no correlation of
the turf growth o r turf d e n sity to soil density.

H i g h e r load

carrying capacity would be expected w i t h the combination of
good turf cover and high soil density.

A better shoulder con­

dition for resistance to rutting or d e f o rmation under load
would follow.

This expected result was borne out in the tests

and resulting d a ta on the plots.

lioisture r e l a t i on sh ip s w er e fcund to influence
Inherent

the

sta bi li ty as d em on s tr at ed in the rutting studies.

The plate bearing

studies did not °hr>v;

^ 7

tion to c o i s t u r e v a r i at io ns on any soil
It is evident

'* r ^ c 1" c o r r e l a ­

subbases or additives.

that w i t h p r o p e r cultural methods,

turf

can be d e v e l o p e d on p r a c t i c a l l y any b ase designed to carry
loads

for h i g h w a y

shoulders o r airstrips.

The p e n e t r o m e t e r studies prove d that a direct cor­
r e l a ti on could be d r a w n so that values of load could be de­
rived to compare

to p l a t e b e a r i n g studies and thus arrive at

values of subgrade m o d u lu s

factors "k " .

The two methods,

l o ga r it hm ic co m p u t a t i o n s and logarithmic p l o t t e d curve data,
show v e r y close c o r r e l at io n w i t h

the choice of method,

p e n d e n t on amou nt of d a t a available.

de­

The p l o tt e d d a t a would

require less d at a w i t h the ass um ed and theoriticr.l

°lope and

shape of th** curve.
It was o b s e r v e d that the h i g h e r the modulus
the p l a t e b e a r i n g d at a the

s moother

the slope of the r e s u lt in g curve
show a de finite

"k'5 was from

th.^ cunrp and the lower

from the data.

The curves

trend and co rr e la ti on of curves for each sub­

b ase and soil a d d i t i v e material.
p i t - r u n gravel were

The 22-A graded gravel and

found to produce curves with a greater

break,

at the l o w e r ratios of settlement

to bearing area dia­

meter,

w h l c n w o u l d lead to d i f f i c ul ti es in graphing.

This

can be ex p l a i n e d by the same assumption that tne p en e t r o m e t e r
could not be d e p e n d e d on to produce reliable ciata in soils
c o n t a i n i n g stones o r foreign materials.

- 62 -

Farther’ tests should be conducted on rates of seeding,
f e rt i li za ti on and variations in seeding mixtures for shoulder
stabilization and airfield projects.
also include

Future testing should

studies of turf growth on compacted subbase mat­

erials wh ich would prove very valuable

for airport work and

shoulder improvements on compacted subbase materials.

- 63 -

J

literature

CITED

..lorrish, P.. H.,"The E s t a b l i s h n e n t and Comparative
Vi'ear R e s i s t a n c e of V a r i o u s Grasses, Grass Mix tu re s
and Gr a ss -L eg um es M i x t u r e s to Intensive Traffic with
W n e e l e d Vehicles".
M. S. Thesis, Michigan State
College, 1947.
Rep or t of Traffic Tests on Turf Base Shoulder Investi­
gational A r e a s at M a c ! i l l Field, Florida.
’Var depart­
ment, Corps of Engineers, October 19<±o.
R e p o r t cf Traffic Tests, Turf and 3ase Shoulder Investi­
gation at M a x w e l l Field, Alabama.
W a r Department, Corps
of Engineers, Oct ob er 1946.
Report of the P r e l i m i n a r y Studies for the Examin at io n
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War
D epartment, Corps of Engineers, Ohio Ri ver Division
Laboratory, N o v e m b e r 1945.
Krynine, D. P., "Soil Mechanics", ..IcGraw-Hill Book
Company Inc., N e w Y or k and London; pp 150 - First
Edition.
Teller, L. V». and Sutherland, E. C., Public Roads,
Vol. 23, N u m b e r 8, 1943.
McLeod, N o r m a n V.'., "Airport Ru nw a y Evaluation in
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H o u s e l , Viilliam S., "A Practical M e t h o d for Selection
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St&te H i g h w a y Department, 194c

Revised,

Michigan

Standard S pe ci fications for C o ns tr uc ti on of Airports,
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13.

Robertson, L. S. and Hansen, C. LI. , "A R e c o r d i n g Soil
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15.

Campen, W . H. and Smith, J. R, , "Discu ss i on on Soil
T e sts for the D e s i g n of R u n w a y Pavements", Proceedings,
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16.

______________ and _______________ . "A A n a l ys i s of F i e l d
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Li d d l e b r c o h s , T. A. and Bertram, G. E. "Field Investi­
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Stratton, J . H. " C o n s t r u c t i o n and D e s i g n Problems",
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Goldbeci, A. T. , "A Llethod of D e s i g n for N o n - R i g i d
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Bannister, D. "The T h e o r y of S t r e s se s and D i s p l a c e ­
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Bousslnesq, J. "A p p l i c a t i o n des P o t e n t i e l s a'L'etude
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22.

Osterberg, J. 0.
A.S.T.I-. S y mposium on L o a d Tests of
Bearing Capacity
of Soils, Special Technical P u b l i c a ­
tion No. 79, 1947. p 128.

23.

24.

F. R. , R e s e a r c h Series N u m b e r 3,

Harrison, C. 1.1. "Effects of Cutting and F e r t i l i z e r
A p p l i c a t i o n on Grass De ve lo pm en t ", P l a nt Physiology,
Vol. 6, 1931. P
- S84 .
Graber, L. F. , "Food R e s e r v e s in R e l a t i o n to oth er
Factors in L i m i t i n g the Grow th of G r a s s e s ” . Plant
Physiol og y, Vol. 6, 1931. p 43 - 7C.

- 65 -

Kuhn, A. O. and Kemp, W . B., "Response of D if ferent
Strains of Kentucky Bl uegrass to C a t t i n g ” . Journal
o f A m e r ic an Society of Agronomy, Vol. 51 1959. P
Lovvern, R. L., "The E f f ec ts of Fertilization, Species
Competition, and Cutting Treatments on the Behavior of
D a l l i s Grasses and Carpet G r a s s " . Ibid, Vol. 56, 1944.
Humbert, R. P. and G-rau, F. V., "Soil rind Turf Re lat­
ionships".
U.S.(I.A. Journal, Vol. 11, No. 2, June

— -w

i

TABLE

I

APPENDIX

TABLE II
DEPTH IN INCHES
P l o t Curve
No.
No.

Area
Q 11 l 11 2"
3"
4"
5"
6"
7" 8" — 2
In.
L o a d In Lbs. f o r abo ve D ep th e

1

1

0

1

2

1

62

76

84

88

99

.75

0

105 138 140 140 148 154 155 158

. 75

3

0

120 154 168 174

.75

1

4

0

140 15b 172

.75

1

5

0

140 168

.75

1

6

0

154 171

. 75

2

1

0

93 121 150 158

.75

2

2

0

108 135 145 153

.75

2

3

0

131 152 153 170

.75

3

1

0

85 127 150 180

.75

3

2

0

131 185

.75

3

3

0

148 152 165 174

.75

3

4

0

149 169 172

. 75

4

1

0

87 121 135 loo 174

.7 5

4

2

0

108 127 141 156 174

.75

4

3

0

148 152 160 174

.75

5

1

0

55

5

2

0

91 114 126 157 158

b

3

0

100 130 148 170

.75

5

4

0

130 141 152 165

. 75

5

6

0

160 168 170 170 171

. 75

96

98

99

88 128 l4l 150 153 165

—

64

_

Lean
Load at
Depth

131

136

138

132

. 75
.75
12 b

i

TABLE II

(Continuer:)

DEPTH in INCHES
i;o .

A rea
2n 3 ,f 4 ”
511 511 7*1 a» — 2
In Lbs,for above Depths_________In.

iu

q h

Load
1

0 110

131 132

155

.75

2

0 118

132 143

154

.75

3

0 120

1*1 152

172

.75

1

0

104 120 136 1*1 150

.75

2

0

128 134 1*1 150 loo

.75

3

0

130 134 1*2 160 176

.75

T_

0

2

0

90 106 115

128 1*2 162

3

0

96 109 125

150 165

1

0

102

138 150 152

.75

2

0

119

13t 152 152

.75

3

0

123

155 172 160

-75

4

0

130

152 180

.75

1

0

120

149 157 157

157 157

. 75

2

0

116

125 15° 141

146 1*6 1*6

.75

3

0

4

0 15 5

151 162 171

1

0

120

152 160

150 150

161 161

2

0

1*0

15.-3 150

166 167

157

3

0

143

161 151

161 161

161

85

96 127 150 165

155 157 154

135

120

.75
.75

104

.75

154 170

- 69 -

^ean
Load at
Dpnth 2 ”

1*6

1*6

.75
.7;
.75
.75
.75

157

D E P T H IN INCHES
P l o t C u r v e ____________________________________ _______ A r e a Lean
No.
Nc.
pu
\n
2”
5 H 4"
5"
6»
7*'
J» ~ —
2 Load a
_______________ L o a d In Lbs, for above D e p t h s _______ In.
Depth
12

1

0

110 122 122 122 122 128

. 75

12

2

0

118 133 131 123 125

.75

12

3

0

131 131 131 130 123

. 75

13

1

0

65

38 115 139 ISO

.75

13

2

0

72 124 154 158

.75

13

3

0

87

118 138 158

.75

13

4

0

118 140 141 158

.75

14

T_

0

79

98 138 144 159 175

. 75

14

2

0

84

98 131 144 170 175

. 75

14

3

0

91 118 136 152 169 175

. 75

14

4

0

127 141 150 158 168 175

. 75

15

1

0

96 140 146 146 156 172

. 75

15

2

0

103 130 168

.75

15

3

0

123 148 168 171

. 75

16

1

0

61

92 124 131 152 162. 171

.75

16

2

0

79 111 129 138 147 156 158 158

.75

16

3

0

79 100 126 138 152 170

. 75

17

1

0

62

68

37 121 138

.75

17

2

0

68

92 121 150 142

. 75

17

3

0

70 101 122 139 152

. 75

17

4

0

80 112 128 l4l 162

. 75

129

118

114

139

101

93

"0 c+

T A B L E II (C o n t i n u e d )

TABLE II

(Continued)

D E P T H IN INCHES
P l o t Curve ._________________________________________ Aret,
g,, 011 7 ,1 Q || __ 2
0 “ 1»
4"
No.
No.
2 11 3"
In.
Loa d In Lbs. for above Depth s
18

1

0

70

84

99 122 140

.75

18

2

0

80

9 3 126 140 154

.75

18

3

0

91

112 126 134 144

.75

18

4

0

108 130 132 138 146

. 75

19

1

0

46

70

88 118 134 152

.75

19

2

0

50

7?

95 127 I 4 O 152 161

.75

19

3

0

68

92 110 127 131 150

. 75

19

4

0

72

92 114 131 150

.75

20

1

0

36

74 100 128 142 154

.75

20

c
•w

0

48

78

95 120 138 151

. 75

20

r?
\
J

0

68

9 2 123 126 130 132 140 152

20

4

0

92 112 123 140 158 178

. 75

20

5

0

92 119 132 144 170

. 75

21

1

0

38

62

81 100 120 138

.75

21

2

0

44

82 112 135 141 148

.75

21

rz
w
'

0

4 4

66 136 152

.75

21

4

0

98 118 129 148 162

.75

oo

1

0

88 110 126 141

.75

22

2

0

108 127 138 139 154

.75

0

121 140 144 150 150

.75

22

- 71 -

Mean
Load
D ep t]

106

82

.75

87

126

TABLE II

(Continued)

D E P T H IN INCHES
P l o t Curve
No .
No.

O'*

_
511
1"
8"
6"
7"
2'1 3 ” 4"
above
D
epths
in
Lbs.
for
Lo ad

Area
— 2
in

23

1

0

128 129 140 152

.75

23

2

0

137 138 140 140

.75

23

3

0

148 149 149 149

.75

1

0

110 110 112 119 120 130

.75

24

2

0

118 118 179 121 120 130

. 75

24

3

0

129 129 129 135

. 75

24

4

0

140 143 151 153 164

. 75

25

1

0

38 100 10 0 118 133 160

. 50

25

O

0

57

84 122 l4<± 161

. 50

25

3

25

4

0

26

1

0

85

2,6

2

0

86 118 140 155 164

.50

26

3

0

91 122 122 141

. 50

27

1

0

79

27

2

0

87 128 154 148

.50

27

*£

0

98 115 13 4

. 60

27

4

0

28

1

0

64

144

.oO

2a

2

0

80 108 108 128 140

. 50

28

3

0

90 128 128 128 140

. 50

24

80

0

139

125

112

. 50

131 140 144

. 50

126 133 140
96 121 139 150 154

89

Lean.
Load
Depth

98 112 136 150 160

112

. 50
117

. 50

100 136 154 176
88 115 1-'

. 50

- 72 -

105

TABLE II

(Continued)

D E P T H IN INCHES
1*1- 2 “ 3"
4"
5"
6 U 7"
8 ir
L o a d In Lbs. for above D e p t h s

No

0"

1

0

66

94 128

. 50

2

0

66 108 118

.50

3

0

80 111 118 1*1 155

. 50

1

0

60

81 110 126 141 156

. 50

2

0

66

85 120

. 50

3

0

70

90 130 131 IL31

. 50

1

0

71

85 129 139

.50

2

0

68

91

. 50

3

0

77 118 140

.50

4

0

68 122 121 12 8 145

.50

1

0

43

72 100 140 140

. 50

2

0

56

80

85

95 137 141

. 50

3

0

61

82

87

94

. 50

1

0

38

68

78

92. 137 158

. 50

1

0

48

64

82

98 130

. 50

3

0

58

77

93 140 155

. 50

4

0

1

0

64

72 132

2

0

65

76

88 130

0

71

80

80

— 2
in.

. 50

120 131 131 131

. 50

80

- 73 -

. 50
88 130

.50

TABLE II

(Continued)

No

D E P T H IN INCHES
_______________________
Area
Q »* 1»
2U
5 ” 4 H 511 6*1 7»
6 H __ 2
Load
in Lbs, for above Depths_____ in

1

0

2

0

68

78

78

88 101 116 144

.50

3

0

86

87

87

88 125

.50

4

0

5

0

96 130 119

1

0

SB

<?

0

77

3

0

*

68

86

70

80

. 50

142 1*2 135

68

. 50

119 119 140

.50

70

70

55

77

77

7 7 77

67

87

82

62

82

82

82

82

0

130

125

116

1

0

91

125 145

168

.50

2

0

119

128 144

168

.50

3

0

131

137 150

152 168

.50

1

0

75

132 139

158

.50

2

0

115

128

3

0

126

130 133

1

0

10 0 142

O

0

115

0

12.8 138 148

82

. 50

130

.50
.50

132

•50
150

.50

158

13* 142

.50

.50
1*3 165

. 50

168

. 50

_ 74 -

II

(Continued)

_

P E P T H IN INCHES
P l o t C u r v e ______________________________________
A r e a Lean
No.
No.
qh
m
pm
5 »
4 i
t 5 « 6h
e» —
2 Load a
L o a d In Lbs, for aoove D e p t h s ______________________ in____ Depth
40

1

0

78 116 137 15S

. 50

40

£

0

96 132 156

a

5 \J

c

0

3 3 131 155

a

50

**0

4

0

41

1

0

60

34

30 138

.50

41

2

0

72

9 4 12 6 148

a50

41

o

0

7-o

94 136 144 15*

.50

42

1

0

72 148 156

a 60

0

75

7.rs

a60

r
w\

30 130 150

. 60

141 144

. 50

^±2
-t~

3

a 50

120 162

4

15 c

90 110 16 5 140 170

loo

a 50

140 166

42

5

0

■*3

1

0

74

43

*
>
c.

0

t> 5 115 128

.50

•
“
*5

3

r~~.
u

91 120 13 ^ 150

a 50

44

1

71 116 146 165

a 60

44

2

0

76

. 50

44

3

0

76 150 150

a 50

‘X*±

*±

0

89

12 J 170

. 60

5

0

90 120 150

36 122 131 140

• cO

* O^

1*0 170

-

76 -

1 r\*

12

.

/0 cf

TABLE

TABLE II

(Continued)

D E P T H IN INCHES
>lot Curve
No.
No.

o«

1"
2"
3"
Load. In Lbs.

fi"
4"
5"
6«» ^
for above D e p t h s

Area
—
2
In.

45

1

0

78

99 130 144 15?

. 50

45

2

0

88 120 120 125 140

. 50

45

3

0

118 122 133 133 140

. 50

45

4

0

120 141 152 152 152

.50

45

5

0

131 142 150

.50

46

1

0

70

46

o

0

74 102 155

. 50

46

3

0

95 124 145

.50

46

4

0

110 110 110 112 122 142

. 50

46

5

0

120 120 119 121

. 50

47

1

0

68

81

31

94

. 50

47

2

0

76

90

90

90

47

3

0

81

90

22 108

47

4

0

120 120 119 119 130

. 50

<±7

5

0

122 120 130 148

. 50

48

1

0

38

42

42

4?

4?

4?

42

42

. 50

48

2

0

40

58

58

60

60

60

60

80

. 50

48

3

0

63

68 182 1?2

. 50

48

4

0

70

70

72

84

. 50

48

5

0

73

73

73

73

48

6

0

. 50

. 50
. 50

- 75 -

107

. 50

90

129 189

125

. 50

80 120 13 5 160 165

73

Lean
L o a d at
D e pt h 2»

101

73

TABLE II

(Continued)

D E P T H IN INCHES
P l o t C a rv e
No.
No.

0«

1" 2"
3M
L o a d In Lbs.

4M

5"
7"
5"
t o r abo ve D °pths

Area
—
2
in.

1

1

0

52

87 116 132 157 168 169

.75

1

2

0

95 118 122 130 130 130 121 121

.75

1

3

0

95 127 159 167 178

. 75

2

1

0

73 121 155 141 162 174

. 75

2

p

0

80 1 1 4 136 158

.75

2

3

0 12 2 160 180

.75

'Z

1

0 111 171 171 171

. 75

o

2

0 122 153 ItiO

. 75

3

3

0 157 180

.75

5

1

0

92 120 155 146 158

.75

5

2

0

97 127 136 1^7 169

.75

5

3

0 121 15<± 154 171 169

.75

11

1

0 102 12 7 127 127 127 125

. 75

11

o

0 150 161 160 160

.75

11

3

0 136 151 152 152 152 155

. 75

16

1

0

78

98 126 157 157 171

.75

16

2

0

87 110 127 138 159 173

. ^5

16

3

0

88 110 128 141 160 176

.75

19

1

0

35

58

79 112 138 151

. 75

IS

2

0

47

67

85 125 140 168

. 75

19

5

0

48

69

85 12 5 15 2

. 75

61

- 77 -

L ean
L o a d at
D e pt h 2“

114

168

127

146

10 6

55

TABLE II

(Continued)

rve
No.

D E P T H IN INCHES
__________________________________ A r e a
0”
1”
2»
3”
4 115 11 S»
7 11 8» —
2
L o a d In Lbs,
for gV>ove Depths.___In.

1

0

82 121 136 170

2

0

98 130 138 146 131

3

0

117 13b 158 178

Liear.
L o a d at
D e p t h 2»

.73
.75

129

.75

1

110

.75

2

150

3

160

.75

1

140

.75

n

142

3

144

.75

1

134

-75

2

162

3

172

-7b

1

120

-75

2

122

3

130

.75

1

10 2

-75

o

110

3

153

4

154

.75

-75

.75

.75

.75

140

l-±2

156

124

137

.75
-7 5 _____

_ 78 -

TABLE II

lot
No.

(Continued)

C u rv e
L o a d In Lbs.
Area
L ean
No.
at 2'* D e p t h
—
2
L oad at
_______________ ___________________In._______ D ep th 2U
1

157

.75

2

141

.70

6

3

157

.75

7

1

10 2

.75

7

2

1 03

.75

7

3

135

.75

8

1

114

.75

8

2

8

3

158

.75

9

1

152

.75

9

2

156

9

3

150

.75

10

1

154

.75

10

2

158

10

3

11

1

11

2

165

.75

11

3

168

. 75

12

1

140

.75

12

2

152____________.75________ 146

6
»

141

. 75

153

- 79 _

.75

.75

l'±6

113

138

156

156

.75
162

TABLE II

Plot
IIo .

Curve
No.

Load in L!>s,
at 2" D e p t h

(Continued)

Area
2

—

in.
13

128

.75

13

142

. 75

13

142

.75

14

123

. 75

14

127

.75

14

143

.75

15

1

125

. 75

15

2

128

. 75

15

3

138

. 75

16

1

93

.75

16

2

112

.75

16

3

125

. 75

17

1

110

.75

17

2

112

. 75

17

3

120

.75

18

1

128

. 75

18

2.

128

. 75

18

3

130

.75

19

1

80

.75

19

2

80

.75

19

3

118

.75

_ 80 -

Lean
L o a d at
D °p t h

■

2”

I

131

130

110

114

129

>3

TABLK II
Plot
No.
20

C u r ve
No.
1

(Continued)

L o a d in Lbs.
at 2" D e p t h
117

Area
—
2
in.

L ea n
Lo ad at
D epth_

. 75
127

20

2

137

.75

21

1

115

.75
116

21

2

118

.75

22

1

127

. 75
130

22

2

13 3

.75

23

1

146

.75
151

23

2

156

.75

24

1

160

.75

24

2

153

• 75

24

3

155

.75

- 81 -

156

TA ELE III
Subgr&de Modulus
Plot
No._______________
1

for 2500 P o u n d Load

Planting
Lonth

G r a s s fix tu re and Rate

65
72
70
57

April
J une
August
October

67
70
69
54

April
J une
August
October

7

73
77
90
75

April
J une
August
October

10

60
61
57
55

April
J une
A u gu st
0 c tober

15

72
70
75
54

A p ri l
J une
August
October

R e d t o p 2b
Lentucliy bluegrass 40

16

82
75
60
55

April
J une
August
0 ctober

Bornestic rye 15
C h e w i n g fescue 40

16

110
90
81
73

April
J une
August
0 ctober

20

67
65
59
57

April
J une
August
October

5

P l a n t e d - 1044
Tested

— 1949

- 82 -

A l f a l f a 8 - Brorne 7 - Oats

B rome ^ra s s 40

K e n t u c k y bluegrass

Chewinr;

0 rchard

fesciie

15

gra?e 40

Tall Fescue

15

40

TABLE V
Plot
No.

Depth
x (1)

Lo a d at
Depth X

1

.176

2000

.228

2500

2250

2

.176

2000

. 2.35

2500

2250

5

.174

3000

.215

3500

3300

4

.182

1500

. 266

2000

1600

5

. 17 8

2000

. 252

2500

6

. 128

1000

.211

loOO

l-±50

. 200

2000

2000

.222

1500

140 0

Q

. 200

1500

1500

10

. 200

2500

2.500

7
a

.131

1000

Depth
y ( !)

L oa d at
Depth Y

Load at
Depth 0.2"

11

.186

250 )

. 232

3000

2.700

12

. 141

2000

. 760

2500

7250

13

. 178

2000

.228

2500

2250

14

.190

2000

. 232

2500

2100

.200

2.500

2500

15
16

.174

2000

. 224

2500

2250

17

.164

1500

.232

2000

1750

18

. 200

1500

19

.160

1500

. 247

2000

20

. 129

2000

. 716

2500

21

.185

1500

.236

2000

1670

22

. 19 6

2500

. 236

3000

2550

23

.16-5

1500

. 212

2000

lbob

24

.188

*±500

. 20 S

50 'O

^tcsOO

25

. 182

5000

. 216

5500

5255

1500
1750
2 *±10

TABL7 V

(Continued)

Plot
Depth
L o a d at
D e p th
No.____ x ( 3.)_____ D e p t h X___ y (1)

L o a d at
Depth Y

Load r.t
D e p t h 0.2"

26

.191

2500

.216

3000

2700

27

.194

3500

.725

4000

.3000

28

.175

2500

.20 5

5000

2^10

29

.188

200 0

.7 74

2 500

2165

300 0

.205

3 500

.210

*±000

30

.173

5 *±20

31

.171

5500

52

.200

2500

53

.182

250C

.214

3000

2800

34

.120

4500

.215

50 DO

4700

55

.192

405 0

.227

450.'

4100

.196

3220
2500

3000

.213

5500

5100

57

.200

S000

60 JO

38

.200

6000

6000

5S

.120

5500

.2 1 6

60 JO

5700

40

.195

5000

.214

5500

5165

41

.191

6000

.207

6500

5250

<t2

.180

o 500

.20 5

■“± 5

.193

4000

.222

4a

.193

5500

45

.200

1500

1500

46

.200

7000

7000

.2^2

4000
4500

6000

4l2i

5625

47
0

. 200

550 0_______ 5 500

( 1) X and. Y are the depth a and eorre sponci inp loaur vvht e;i,
when interpolated, e^'ive tne loaci at the a epth o l ‘
J . n incr.es
-

84 -