AN EXPERiMENTAL STUDY
OF sou. DENSITY
BY THE ‘PROCTOR METHOD

Thesis for the Degree of B. S
MICHIGAN STATE COLLEGE

Joseph ]. ‘Ventura
' : 1940

‘‘‘‘

 

An Experimental tudy of Soil Density

by the Proctor Method

A Thesis Submitted to

The Faculty of

MICHIGAN STATE COLLEGE
of

AGRICULTURE AND APPLIED SCIENCE

by

JOSEPH JOHN_y§gTURA

Candidate for the Degree of

Bachelor of Science

March 1940

\£{f]!$

 

0363. I

 

TABLE OF CONTENTS
Introduction

Plastic Limit

Liquid Limit

Plastic Index

Liquid Limit Graph

Specific Gravity

Field Moisture Equivalent
ASpirator Moisture Equivalent
Shrinkage Factors

Mechanical Analysis

Analysis Graph

Compaction Tests

Compact io n Graphs
Conclusions

Comparison Graphs

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SYMBOLS

Plastic Limit

Liquid Limit

Plastic Index

Specific Gravity

Field Moisture Equivalent
Aspirator Moisture Equivalent
Centri fuge Moisture Equivalent
Moisture Content

Weight of Wet Soil'

Weight of Dry Soil

Shrinkage Limit

Volume of Wet Soil

Volume of Dry Soil

Shrinkage Ratio

Volumetric Change

Field Moisture Equivalent
Lineal Sh rinkage

Volumetric Change

HygroscOpic Moisture

The oldest and yet the most complex construction
material known to mankind is that material known as soil.
In spite of the long use of soil as a construction material
comparatively very little is known about the physical perfor-
mance of a given sample of soil.

It has been due to this lack of knowledge of soil
acti on that hundr eds o f miles of highway have disintegr-
ated and a large number of earth dams and embankments have
failed to live up to the ir predicted perfor mance.

One of the largest fields of engineering in which
a knowledge of soil mechanics is required is the design of
embankme nts and of earth dams.

The Bureau of Waterworks and Supply of the City of
Los Angeles became interested in the problem presented to
the m in the design and construction of earth dams and in
1933 pub lished a paper written by R.R. Proctor, who was then
an engineer for the Bureau of Waterworks and Supply, which
set forth a principle showing that there is a fixed relation-
ship betweenbthe water content of a soil and the denseness
t 0 which it may b e compacted. This relationship soon proved
to be one o f the mos t satisfactory methods of construction
co ntrol available and was soon in use on most construction
projects where compaction was necessary,

The results arrived at by this experimental study
are b ased upon t he relation of moisture to density as shown
by the work of R.R. Proctor in his investigations at LOs Ang-
else.

The reader of this paper must realize that a soil
is not a perfectly homogenous material, although this ass-
umpt ion is sometimes needed for a solution, therefore a num-
ber of solutions on what one may believe to be similar samples
of a soil, may show a variation that can approach 200 percent.
Howe ver, even with this possible error the solution will
be more dependable than the old, empir ical, rule-of-thumb
met ods used by engineers up to a comparatively short time ago.

-2-

The soil used in this experimental investigation
was a sample of soil taken from the Strathmore Sub-division
in East Lansing.

To determine the t ype of soil used and some of
its physical characteristics, the following tests were used.

Plastic Limit T-90-38
Weight of Cont ainer ----------------------- 33.05
Weight of Container and Wet Soil --------- --5 2.26
Weight of Container and Dry Soil ----------- 49.30

Weight of Dry Soil-------------------------l6.25

P.L. ngoss in.Weight x 100 u 2.86 x 100 g 17.60 %
Weight of Dry Soil ' 16.25

The Plastic Limit determines the lower limit of the
plastic range and i t is important because it supplies defi-
nite notice of the change in state of the soil mass.

Liquid Limit T-89-38

Weight of Co ntainer--~------—-----------------------3l.08
Weight 0 f Container and Wet Soil--- -------- ---------57.65
Weight of Co ntainer and Dry Soil--------------------49.28
Loss in Weight-—------------------------------------- 8.37
Percentage of Moisture-------------------------------45.98%
Number of Blows-------------------------------------—19

Weight of Container and.Wet Soi1---------------------53.19

Weight of Container and Dry Soil---------------------48.16
1,088 in weiSht“not---nun-uncann-“c-uuuuw-nnucnuuum 5.0}

Percentage o f Moi sture-----—----- -------- ---------31.97%

The Moisture Content at the liquid limit is the
amount of mtisture needed to reduce the soil mass to a semi-
fluid condit ion and therefore represents the saturation lim-
it of a soil.

Plastic Index T-91-34
P.I. a L.L. - P.L._r 42.5 «17.6 2 24.9

The Plastic Index is a measure of soil cohesion.

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-4-

Specific Gravity T-lOO-38
Weight of Pycnometer--- ----------- - ------------------ 13.6487
Weight of fiycnometer and Water-----------—----------63.6590
Weight of 'cnometer and Water and Soil----- --------- 70.1215
Weight of oil ------------------------------------ ---10.0007
Hygros copic Moisture ----------- -----------—--------- .1340
Specific Gravity-(25 deg. c.)-- --------------- ------- 2.7221

S.G. , 10.00 - .1 40 : 2.7221
E? 73.5257-7d.i215

The Specific Gravity of A Soil is the we ight per unit volume
of the material to the weight per unit volume of water.

Field Moisture Equivalent T-93-38
Weight of Container --------------------------------- ~32.80
Weight of Container and Wet Soil ---------------- -----42.67
Weight of Container and Dry Soil ----------- - ------ ---41.99
F.M.E. : 42.6 - 41.0 500 I 19.06%
1 009-32 0 0

The Field Moisture Equivalent indicates the quan-
tity of water assoil is likely to take up under field condi-
t ions 0

Aspirator Moistu re Equivalent S-3
Weight of Container --------------- --------- ----- -----38.55
Weight of Container and Dry Soil ------------- - ------- 37.16

370 - 33020

The aspirator moisture equivalent is equal to the
Gen trifuge Moisture Equivalent. Theaspirator moisture equiv-
alent was used as a«centrifuge was not available. It gives
infotmation as to the relative porasities 0r draining qual-
ifications of various spils.

Shrinkage Factors T-9 2-38
Weight of Dish------------- -------------- ---------- 9.92
Weight of Dish and Wet Soil-- ----------- ------- ------ 32.17
Weight of Dish and Dr y soil -- ------------------- --24.69
Weight of Wey So il----------------------------------22.25
Weight of Dry Soil--------------- -------- ---- -------- 14.77

Volume 0 f Wet Soil--------- ----------- - ------------- 13.90

-5-

 

 

 

 

V01 ume of Dry Soi 1 -------------------------------- 8. 50
Moisture Co ntent ------------------------------------ 50163
Shrinkage Limit --------------------------------------- 14.07
Shrink age Ratio ------------------------------------ 1.47
Volumetric Change ------------------------------------ 7. 33
Field Moisture Equivalent ---------------------------- 19.06
Lineal Shrinkage ------------------------------------- 2.20
Specific Gravity ------------------------------------- 1.80(0ut)
w ; (W-Wo) 1 00 (22. 25- 14.771100: SO. 63%
W0 3 14.77
s 2 w - (V-Vo)100 _50. 63 - ( 13. 90 - 8. 50#) 100- 4
we - 14.77 1 O7

R-fl—II4ZSZCZ).147

v.0. - (w1-8)R= (19.06 - 14.07) 1.47 . 7.33

 

 

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L.S. . 10021\J* 100 &_ - 100(1 - 100 o .20
Cf 1-1 00 or 1 #100)
S.G. 3 1 - 1 $4_:_ :1.80 (out)
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"R“ ‘100' "1.47 100

The shrinkage limit is that amount of water that
is required to fill the pores of a soil sample which has been
dried to constant weight from a momsture content required to
fil 1 the pores comppetly.

The Shrinkage Ratio is the ratio between a given
volume chan ge and t he correSponding change in moisture con-
tent above the shrinkage limit.

The volumetri c change is the volume change when
the motsture content is reduced from a given percentage to
the shrinkkg e lim it.

The Lineal Shrinkage is the decrease in one dimen-
sio n when the moisture content is reduce d from a given
percen tags to the shrinkage limit.

Mechanic a1 Analysis T-88-3 8

Hygrosc0pic Moisture
Weight of Can ------------------------------- --------33.07
Weight of Wet Soil and Can -------------------------- 45.80
Weight of Dry Soi 1 and Can -------------------------- 45-63

H.M. : (42.80 -4§.622100 = 1.34%
50 3 " 33007

-5-

Coarse Material

Eraction retaan ed on #10 sieve,
percentag e of c orrecte d weight of total test sample- 8.56

Sieve Analysis

Sieve Number

Sieve Opening ”eight Retained

Weight of Total Test Sample, air-dried, grams, -------- 101.24
Weigh t of washed and oven-dried fraction

r etai ned on #10 sieve -------------------- ----- ----- 8.56
Weigh t of Fraction passing #10 sieve--- ------------- 92.68
Weight of fraction passing #10 sieve

corre cted for hygroscopic moisture ------------------ 91.44
yeightof Total testtsample corrected

or hygroscopic modsture ---------------------------- 99.90

Weight of fraction retained on #4 sieve -------------- 0.00

% retained

 

 

 

20 .840mm . 1.20
40 .420 2.58 4.78
60 .250 5.78 10.71
140 .105 11.6 5 21.58
200 .074 13.28 24.62
Passed 200 .07
Hydrometer Anal ysis
Time Theor. Temp. Orig. Corr. % Disp. % of K1
(min) Grain Hyd. Hyd. Sample Size
Diam. ‘__ Rdg. Rdg. in Sol.
1 .078 ‘25.5 31.8 34.05 69.75 63.47 .494
2 .055 25.6 29 .9 32.20 66.00 60.06 .498’
5 .035 25.6 25.9 28.20 57.80 52.59 .507
15 .020 25.6 19.5 21.8 0 44.70 40.67 .521
30 .014 25.6 15.6 17.90 36 .70 33.39 .530
60 .010 24.9 13.3 14.90 30.55 27.80 .546
250 .005 25.6 5.6 7.9 0 16.20 14.74 .550
1440 .002 25 .6 .1 2.40 4 .82 4.38 .561
K2 Kn Grain Corr.
Size or. Grain
Facton Diam._g
1106! 093 0469 .0 37
1.02 .9 3 .473 .026
1.02 .93 .482 .017
1.02 .93 .494 .010
1.02 .9 3 .503 .007
1.02 .94 .524 .005
1.02 .93 5522 .003
1.0 2 .93 .5 33 .002

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-5-

From the foregoing tests we see that the soil
8 am ple can be classified as an A-6 soil, according to the
Bureau of Public Roads Classification. The soil sample used
has more than 30 % of clay, it has a liquid limit gxlthlx
greate r than 35, it has a plastic index approximately equal
t 0 26 which is derived from the formula given by the Bureau
of Public Roads in their classification chart. This formula

1.07 1.07

It qualifies as to shrinkage limit by the fact that it does

not exceed in appreciable amount the val ue der e b the

formula s: 21 - 1.1 L.L.- L.L‘: - 21 - 1.1§42.5—42.§"= 13.7
00

 

800 -

It qualifies as to field moisture equivalent beqause_it_apn=__fi

r caches the value given by_the formula F.M.§.= 15.2(L.L.-l6.3) 1 S
which is equal to F.M.E. 9 \[15.2( 42.5 «16.3)‘ 1 9 :28

It qualifies as to centrifuge moistu re e qui valent as it

lies betw een the values of 51 which is derived from the

equation C.M.E.:L.L.-l4 and the valueof 30 which is derived

from the formula .55 C.M.E.=.72 L.L..

Theref ore from the graph of the mechanical analysis
performed and from the chart of the Bureau of Public Roads
it is seen that the soil used was a clay soil with little
coarse material.

-9-

After the soil type was determined, Procto r Com-
paction tests were made on the soil with the following
data bei ng obtained.

 

 

 

N0. of % of Wt. of Wt. of Vol. of DE NSITY Penetration
Te st Water MO 1d 3011 Mold WET DRY
& Soil
1 10.10 3419 1934 1089 1.77 1.61 580
2 11.95 3435 1950 1089 1.79 1.62 435
3 15.07 3527 2042 10 89 1.87 1.63 200
4 15.75 3555 2070 1089 1.90 1.64 152
5 16.01 3568 2088 1089 1.91 1.64 140
6 20.20 3692 2207 1089 2.02 1.68 72
7 20.56 3696 2211 1089 2.03 1.69 68
8 22.91 3641 2156 1089 1.98 1.61 54
_9_3 27.91 3511 2026 1089 1.86 1.46 :go
Cangfi
No. of 2:32 Wet Dry Loss WT. of WT.of APP
Test Kflfi WT.I_ WT. HOH Can Dry Soil H2QZ
1 2 51.17 49.53 1.64 33.28 16.25 9
2 42 53.45 51.22 2.23 32.59 18.63 11
3 2 6 56.26 53.16 3.10 32.55 20.61 14
4 41 49.08 46.76 2.32 32.05 14.71 15
5 39 58.94 55.17 3.77 31.62 23.55 17
6 6 66.15 60.60 5.55 32.99 27.61 19
7 38 57.38 53.04 4.34 31.95 21.09 22
8 82 55.32 50.96 4.36 31.90 19.06 24
EL 98 70.83 62.53. 8530 432.86 29.67 130

 

The above data w as collected by using a fresh sample
for each compaction. The results are shown on the following
graphs. The following data was collected by running compa-
ct ions on the same sample of soil, the soil being passed thru
a #4 sieve after each compaction.

 

 

 

No. of % of Wt. of Wt. of DENSITY Penetration
Test HOH Mold& Soil Vol. of WET DRY

Soil Mold
10 12.10 3543 2058’ 1089 1.88 1.67 *410
11 14.95 3630 2145 1089 1.96 1.70 200
12 18.30 3739 225 4 1089 2.07 1.75 90
13 19.51 3761 2256 1089 2.09 1.74 80
14 20.60 3737 2252 1089 2.06 1.70 70
15 24.20 3625 2140 1089 1.96 1:57 65
No. of Can.# Wet Dry Loss Wt.of Wt. of App.
Test WT. Ht. HOH Can Dry So 11 HOH
10 ‘7 6 46.73 45.03 1.70 31.05 13.98 13
1 1 8 58.21 54.88 3.33 32.61 22.27 14
12 17 49.86 47.31 2.55 33.40 13.91 19
13 26 ' 55.71 51.87 3.84 32.65 19.22 20
14- 32 60.23 55.15 5.08 31.51 23.64 21
.15 41 61.27 55.41 5.86 31.21 24.20 26

 

 

 

 

 

 

 

 

 

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-12-

A check back was made on the soi 1 sample to see
if it wo u 1d ret urn to its former state after it had been
thhu a number of compaction tests. The checkback was start-
ed at a moietureecontent of 18.30% and the soil was allowed
to dry. As the soi 1 dried out, compaction tests were made
and recorded. The densities nxkxnad obtained on the check
backs were greater than th e proceeding mm densities. The
results 0 f the che ck back are show n on the graph on page
1 1 and th 3 data 1 6 recorded below.
Sample # % HOH Wt.of Wt. of Soil Vol.0f DENSITY Penetration

 

 

 

Mold & Mold WET DRY
Soil
16 12.21 3560 2075 1089 1.905 1.69 425
17 15:60 3652 2167 1089 1.99 1471 150
Sample Can Wet Wt. Dry Wt. Loss of Wt.of Wt. of
' # # ., Water Can Dry Soil
L67 79 50.09 48.07 x2!R2.02 31.56 16.51
17 64 54.01 51.15 2.86 532.83 18.32

 

The action that takes place as the soil is compact-
ed at different moisture contents is as follows:

When a soil is compacted at a low moisture content
it will be firm and hard. Its relatite hardness in relation
to the othee compact ions is shown by the penetration curve
which shows high values for 10w moisture contents. If the
moist ure content is increase d and the soil compacted, there
will be a r earrangement of the soil particles of various
sizes because 0 f the increased lubricati on provided by the
water. This sample will contain less voids, will be denser,
and will be more plastic. The moisture content can be inc-
reased with bennixttnxxi beneficial results until the part-
icles are rearranged so that all the void space is full.

When this occurs the soil is at its maxi mum densi ty. The
moisture content at this point is called the o ptimum moist-
ure co ntent. It is thus seen that the moisture content of

a soil contr ols the density of that so i 1 and thru the den-
sity it controls the voids. This principle is of value wher-
ever st ability of soil is required, as the most stable str uc-
turs is obtained where the moisture content is that that re-
sults innthe least voids wheh the soil is compacted. Redi-
cing t he voids i n a soil structure also reduces the channels
of flow and thereby makes the structure more watertight.

I noticed that in running the check back on the
soil, the penetratio n resistance was higher for the same
moitture content on the checked back soil than on the soil
that had not been allowed to dry out. This can be explained
by the fact thatif saturat ed clay wer e permitted to dry,
the watee loss would progess inward. As the void water is
progressively reduced, realignment of the part icles becomes
possible and under the compressive force of cappillarity, the
soi 1 would shrink. As the soil shrinks under the influence

-13-

of capillary force, the particles are brought tightly togeth-
er, resulting in increased molecular cohesion of particles
and a consequent increased stabili ty. If th e sam e soil
is wetted agattnn again, the reformatio n of the films may
result in the almost complete loss of this stabilizing phe-
nonoma so that the soil is less stable than it was before
drying, although of the same water content.

The soil that was used in the second part of this
investigation was passe d thru a #4 sieve and reused for
each determination. In all cases this sample gave a higher
density for the same moisture content than when e a fresh
sample w as used. This was because of the gr eater chance
the particles,in the so i1 which was reused, had to realign
themselves. The soil that was used over and over also
showed a higher stability than the soi 1 in which a fresh
sample w as used for each determinat ion. These results are
shown on the graph on page 14 and 15 .

 

 

 

 

 

 

 

 

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