DRILLING AND BLASTING IN THE
DEVELOPMENT PHASE OF
“ETAL “WING

Thul- for the Dogm of B. 3.
MCI-[MAN STATE COLLEGE

P. J. Rockenbach
194.7

 

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A Thesis Submitted to
The Faculty of
KICIITSI STATE CC LEG:
of

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sJQL U'J;I‘~.‘$J ‘ _..&' it; *‘J‘H‘lr‘ ‘9 ‘JII‘JH

E“. J. Eloclzcnbach

‘ _....r:

Candidate for tho Yogree of

EacLelor of Science

Icccm“er 1047

'JHESlt-b

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Chapter
I.

"FT

III.
IV.
V.

VI .

r-r'v-
.24..

VIII.

IX.
Appendix

A.

D.

Go

 

3
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3‘15
1&5 34

‘J ‘&‘~I

III BACK OF BOOK

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In the preparation of this thesis, it was my in-
tention to complete sufficient research so that I would have
a knowledge of some of the basic funlamentals used in the
theory and practice of drilling and blast: 3 in.netal mines.
fly training and experience have not been such that they
would qualify me to quote even a small part of this tgesls
from first-hand knowleCQe. Therefore, the contents are pure-
13 of a library research nature. I believe, however, that
this paper has been well worth my time if only for the fact

hat I have gained a rudimentary haeggreznd in a fiele of
agincering wnicn.may be of use to me in the future. Inas-
much as I could not locate any material on this eubject at
Elenigan State College Library, his thesis may also prove
to be of some benefit to any students who may be interested
in tne subject in the future.

then one considers the enormaus amount of labor,
power, ed powder required to mine and to quarry products
annually, one cannot fail to be impressed with the scanti«
nese of literature on the economics and procedure In the use
of explosives in metal mining.

fhe following ftjuree will serve to illustrate the
importance and magnitude of this industry. or the 530 odd
million pounés of dynamite manufactured ourTng 1340, con-
struction work used 103,330,030 pounds, metal mining 100,030,090

pounds, quarrying £0,300,030, and coal mining 85,000,090 pounds

of dynamite plus 63,000,000 pounds of black powder. .no
rest was used in non-metallic mining and agricultural work.
Upwards of 55,000,000 pou.ds are used to mine crude ore con-
taining either gold, silver, cepper, lead or nine. Twenty
million pounds are used for iron ore. Iynauite is beinz
fired every hour of the day in charges ranging from a few
ounces in the coal nines to great 50,000 pound explosions
such as those used for blasting valuable molybdenum from
Colorado's Eartlett flountain.

fietal minim; operations are usually of four types:
preopecting, exploration, development and pro uction. Fros-
pecting involves the location of ores, and exploration the
determination of the extent of the ore bee . blasting may
or may not be employed in prospecting and eXploration. Te-
volopment is the work nvolved in providing access to he
ore and in providing for systematic removal of the ore body,
transportation, ans ventilation. Froduction comprises re—
moval of the ore on a commercial basis.

Ky original intention was to include all four of
these operation in this tllesis. Elowever, as I learned more
about the subject through research, I found test it would be
necessary to limit the scope to one particular phase. Inas-
much as the devolOpment phase seemed to offer a more repre-
sentative example of drilling and blasting proceeures, I de-
cided to limit my subject to tnis phase and present a more
complete picture than could be done otherwise in trying to

encompass the whole subject.

‘13- 1'71"" ”‘9' .459"! F“Rf‘ ':
OP .J.~T‘1'3TLO.::‘ J .i at.“ s “44”? IJLO“ - .ai; b. 1.18 Jo;

As stated previously, the work which is included
in the development phase is tiat wLich is necessary to pro-
vide access to the ore and provide for systematic removal
of the ore bocy, trazzsportation armi ventilation. fevelop-
ment operations consist of rifting no cross-cuttin: , raising
and sinking. These differ from the usual tunnelling and shaft-
sinking Operations only in that they are frequently smaller
in cross section and that less emphasis is laid on the speed
or advance. Al though drifting, raieiig and sinking Opera-
tions are all included in the Cevcloymtnt stage in this paier,
th stress is placed upon the drilling and blasting of drift
and cross-cut rounds. This is tLe most important operation
and the procedures used in raising and sinking are nearly
identical, witn a few exceptions that will be noted.
Prifts and Cross~cuts
frifts and cross-cats are Lorisontal t“*nels of

varying cross section but usually much smaller than railroad
or vehicular tunnels. A drift will follow the Lirection of
the vein or lode and a cross-cut is ariven across the trend
of the vein or formation. Thegr may be criven for haulage or
ventilation purposes. Strictly socaLing, an inclt sive term

u.at co wli be applied equally to a round in tLe face of each
would be "horizontal Lead’ne roun’", but such a designation
is seldom used. fetal Livers in general refs r to a ro~ d i
a horizontal heading as a ”drift round", one this designation
is used in tLis sense tLrO‘eh ut the

‘)A‘

paper, irrespective of

whether the Leading is a drift or cross-cut.

Raises
As the name in¢1catcs, raises are small 13333303
driven from a lower level to a h1;hcr level. ?Ley may vary
in inclination from vertical to nearly horizantal 333, of
course, all drill holes will be p3int1n3 upward. They may
be driven for drainage, ventilatian, chutes and other pur-

20308.

£222.23.

“inking includes shafts and wlnses, which are
passageways sunk from 330 level to a loubr level. Shafts
are 3L3_lJ sunk vert sally and in a straight line as they
are usually used for raising and lowcring material. Klnzes
are almost alwa*sw131: 333 31d sold3m straight. They are

used for explorfition, ventilation, or manways.

The term "st0p1n3" may be used at Lntc rvals through-

out tLG paper, althaa 53.}1 it is a part of the uroulut on rather

I!

than the Levels“L-3t :hase. It is defined as mining the

mass of are between the levels’

3.. 934;: TI 3?: 0:? :J:;; Ia“ Ju {31.3

Craros and 3333307133

 

3: ing ex 1:7losives may be roughly Lizifled into two
classes - those thet.heve a heavin3 effect and tgoss that
Coliver a shatterixg blow. Black powder, an exyleei.e of
the first class, :18 31°03 12:21.1; “33d -11 qusmry WOT}: whore
tge retoriel to be moved (1339 not require 5 uttering. Kore-
ovor, in quarry work .wo 01' more free faces are usually pro-
vlfiod. A high explosive, such as a d;n flitc, which will
shatter t.e rock is reqv’red for break-n;m .ost .;etal 313135
rounds.

.39 91.1% ves meet c01w131l; used for unflcrgr3unfi
work are gelatin and ammonia dynamites. Gelatin dyn1mits
consists of nit303lycerin which has been gelstinised by the
addition of nitrocetten, 533133 nitrate, and carbon carriers,
such as wood pulp or flour. This is most pepulsr for mining
hard ores an‘ all kinds ef'unlc rgreund work where the venti-

lation is poor and work must be carried on at high speed.

COIL” in Gynar:lto 1m t: yro:e-.y of :wl s. icity‘which en-
ables tLo m11.t3 make the cartriflge stick in holes drilled

upwards - a great a 733.3‘0 in stoping and re se work i
metal.mlming. It is 3:33 t'cally un””fccted by ester and pro-
duces a smaller amount of fumes than other types of dynamite.
there the ore is very hard, gelatin fighamite is used because
of its hiMH dens; by, th t is, it is possible to ceneentrem

the maximum weight of explosive material in a small syncs.

1:? onia dynsmi to con: ets of n'tro glycerin, soCiHm ultra to,

ammonium Mtrete, and C3333 tible n1steriel. It is used.in
iron ore mining, qearr in: and constru cti overt, coal
mining and wherever tLo ventilation is good and litt-le aster
is encountered. Both tLe gelatin and ammonia dynamitcs are
made low-freezing by the ediition of a small amount of nitro-
cellulose

Straight dynamite, which is not orfiinerily used
uneeo"reunc because of t; e comparatively large quantities
of carbon monoxide in the gases 0; exglosion, Consists of
nitro;lyccria, sod; 3.3 nitzate, see wood pulp or other com-
bustible materiel. Lhile it is tr‘e tLet tLe straiglzt cinn-
mitos are the quickest acting and.most sLatterin; of all ex-
plosives, tLey ere more exgensivo, more sensitive to sLock,

end in :en oral presses m 10 fumes than gelatin enfl ammonia

the grade of a strelglt nitr031ycer111C3meL1te

is indicated by the pc11ccnt go of nitroglycerin in tLe ex-

:cloe ive, for instance, a 13 per cent straight C3r smite con.
tains 43 per cent of nitroglycerin. The 3; secs cesijnuted
for gelatin or ammonia dynamites are more or less urbitr
end are suppose& to be eqsivslent in stren 3th to the corres-
pond1ng grade of straight dynamite. fiesever, each manufac-
turer follows his own standard, and too differer t cheds of
gelatin Cynuxfi te marlzed "40 per cent strengthV may not have
the some Llestir; strength and.ms; also dl1fer in other
characteristics. 1he hiihcr grades 01 explosive have more

propulsive strength; therefore a greater amount or blasting

enor5.y can be cantaincd in a 5lven $9303 each as the bore
of a drill hole. Koreover, the higher grades 503933113
have a hi5her rate of dotenation, which 18 an advantage in
blasting at many mines.

In general, one of the 33:3 C3neiderutions in
choosing an explosive for uee underground is that the pro-
:‘cts of 039103 'on shall cen‘ain 3 ml.’ liizum of pois3naua
53303 and smoke. There has been a 53'a&331 PULuLL on in the
$uantity of poisonous 53303 in tLo products of 033103133,
and in this reapeot the 03zp103l v03 now used are much superl-

tJ those in general use several years a5o. Sven with
the present explosives, however, oneu; ; toxic 533 is pre-
sent in the utmo 33030 9”23r blasting to require of? ctivo

ventilet;on to remove it before non return to work.
Stronjth or ?rossure Toveloped

?ho strength of an eXp].osive is apparozltly the re-
sult of three factors: (1) The heat 5enerated, (2) volunw
of 53333 produced, and (3) 35303 at which the gases are
evolved

The pressures C0?610ped in bore holes with vari-
ous explosives have been calculated by the Bureau of Kinea
as follows:

1», . v. ,
§Odnm8 per
303333 in.

50 per cent strai~Lt nitr0"1ycerin dynamite 120.2 30
43 per cent 5elat; n “Jumu-to 120,110
40 per con stral5ht nit 05lycori n ‘"namite 121,050
40 per cent anaemia dynamfte 126,330
50 per-cent atr31~ht nitrO5lycer1n 133,300
60 per cent strai 5‘Lt nit3051m' :13 13;,6'70

It should be barne in mind. that 831:" C explosives may 1:111-

‘ n, . - --. . on - w .. L I? ‘ —, ‘21“. L,
cute stron sh or 0"; -.cr q u11‘y LLUR QCStCu thLP lawanaLory

«a (Lab

L 1‘-.. 1-2- u ' «4—.
CJnditioas u1 bphgae L14--rL. tIJ 1n fibulal

C": 1", 171030 figures do 33:03:: tin: catty. 1:" tivo strenfim of the

“a HP!
Vt-Li‘n'ul‘

Q ,3 ‘6 1 ‘ _$ n’? .—
"r; :11 5730.1. ‘3 01 (1-;sz 1.1.0.

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The explosi'o us 01 for bla.s Zn‘ rauids 311:1: be

h)

pm“ u; in castr1djcs 0: as large diaxctcr as can easily be
loaded inta tgo drill Lolcs. In haré g23"11, ngaaltj 0?
1031133 13 vcryl m12'; t;;:t; the groatoo' Lc;5:‘tv can b“ ob-
*a1n01 w: th.tL' 13:;ust £1;uctor cartriigcs 113% will

gilt-3 t0 2.13103.

n '2" . ‘ A -".- "I ~. -‘o n '.- - - fi '- nu
:‘C=OJ‘.OH 0- LL; $111Lt 01 two rape: 3J.11

J—

3
a
"1

t3 tLo woith of 21amctcr and

.‘n 9 - .. 2. s
the '1wlo"" -ncruaces as 110

f5.

lon;.h are chsca Cd; t1orcfo“u, w1'h sdallu L““ :3 a re-
latlvcly 'rgcr m_:3‘“t ). paper 3:.3 le 33 03:1331ve is pur-
c? sea in cash case. 1 t;ou;h the paper eater int) 1L0
reaction of the czjlosivos as a afifibon ca1210r, it is an un-
:.;.-....;d 1115:1"M31021t 0.1241 13 rosyoncribla for part at 1.1351: of the
p03. 33 Ions gases in the products of C" 13810: A180,U"T”t
for weith, the paper probably s:p;ullos a 3 explosive cner
33 tLan w ulfi a corros:ond1n3 amaunt of a carbsn Carrie - 1n-
timatccly1111xod u tn the ox; 10L1¢0o

tan: mi.crs ca11fier a cartridge a cartriigo and
will use the SJHC nunLur for Ll:st1n~ a 31'.‘ n r0111, regard-
less of $10 3120 of tLe stick or kind and graae of on; slosive.
Lowcvor, wlmro blast1:3 is c103 clJ alporvised bott or reszlts

should be obtained by using larger cartridgca.

Selectio:1_g§ an ixgloeive

 

Generally there 13 some particular kind and grade
of explosive that w alt bet m-e most ecor omical to ~r'o for
any liven :1 see of worl. As the conditions in most vines
vary greatly, a l r3e number of different cxploof"os would
have to be kept in et~ck if .Le best ..... ml for each particu-
lar place were used. Generally one, two, or at the fiOSt
t;.reo eroloeivos are c-.oson, onion will give tLe best ever-
ago results through ut tLe mine. Gelatin dynamite has a

rLMoor of cLerac orietice that rage it desirable for anaer-
frouné work in metal mines one tuenols, and it is more com-
monly used for the purrose tuen any other ex;losi"e. The
nuttzrel ineensltivenese to detonation of these dynamitos is
largely overcome by the use of stren3 detonators. Anwonia

dr:1a:=.1te es pncxed 1n certriijea 1s often rather hard and

..J.

i.)

consequently more «if: on t to temp than gelnth dynamite.
Its lack of plast1c1. My fin :83 it less desirable for loadiee
hol es steeply 12-011 nod upward. 2L1s close of explosive

takes up moisture unless 1t 13 protected. immon1a dynamite
3onerally has an advalta o in e loxvor cost per piund for a
corres_: ond1n3 grade. its greater bulk as compared with gela-
tln dynamite may be of adventa3e in blasting horizontal slab-
bln; holes where it 13 desirable to Lave the exp lo.-1vc Cle-
tributed e1 23 as much of the length of the bore holes as
p05: 1ble. Ammonia fiynau1te may also he better than gelatin
Ior blaet1n3 in sprl 3v or spongy ground.

Practical experience one shown that stre13ht dyna-

te 18 more dan3oroue to handle tuan 3e: atin. Undoubtedly

q 2 ‘ "- VV~ ; -.\ . - 2 "~30 v v 3 ‘ ‘D u-
a be: of et~a .mxt 31333119 1: “ore 1-301; to ecu note on

30113 drorpefl the1 13 a 31x of gelatin.
blast; . in LQS’-u““fl n: r 3:, 35 e? 13 per
cent 3rade 0.3 31031"e 13 3enerally ehos Sven lower 3rades

031 be used aat-.-ne13“11 for ble t1n3 store holes in easy-
bm 0331 3 3r043d. In Crounfi difficMI to break, 50 or CO per
cent gelatin is usually better. The use of higher 3.?3103,
60 to 80 per cent etreu3tF1, 1n eke out holes makes possible
the breexl 3 of lon3or rounds 1n moot elm see of rock. Those
higher grades also zlve fewer boulders . hen use 1n blasting
1n herd-ore stapes. An 89 per cent firedo ShOlli not he used
unless the V0! atllatlon 13 very good.

Only e"plosivos that hetre been proved to be rela-

1 ;

tively safe to be handled and loaded enoulfl be used in mines.
ther th1n33.b01n3 equal, the choice of ex:1osives resolves

1t3e-f into one of cost. Alt houjh more ener3y per_dollar
can be purchased 1n the Lijher grades, it 13 not economical

to use a more exyeneive explosive where the work can be done

as satisfactorily with one cost? :13 less per pounfl.

-1 11-

VARIOUS TYP4S OP CUTS

Blastlzl3 ‘n u undcr3round doveloymont heading
is ulw l;s ti3ht. There is only one free Paco to which the
ground can be brok n and this is usually of limited size.
T10 first and most difjicult stop in blas“1nj .nyx izoad n3
is to make oz; Opoulng into tho solid 3round, usually in the
ccutcr of tho loco and as deep as practical to adssgzo the
face at one tlmo. TALS Ogcnln3 is called too "cut“ and al-
Lhou3h cuts may be pulled by a nunbcr of methods of grilling
and blasting, too] all servo tho same purpose, namely, to
form.a second frco face to which tho N"O cinder of the holes
in a round can brook. It is thoruforo obvious tlst tho out
is the most csscntlal part of the round as 1L0 root of the
Lolcs cannot possLbl3 p111, unloss tic cut comes ozt cao~
plotuly.

Tho dcsl3uction of the holes in 3 round vary with
the Idil.lld l mincs. Xowcvcr, the torm1n0103y used in
this pa; ? for thcm c holos is as follows: -hc fl1st holes
to be blostcc in a rogn; c120 calls & tho "cut holes". The
holes imncdi ctclv above the cut holcs are called "breast
holes". Tuoco C11llcd nc:: below the cut holes are £0313—
‘notcd "shimmcrs”. The holes at the top of the face are
called "back holoc" and those at the b0 tom "lifters". fix-
tra hole 8 drilled to ass1st &“7 hole or set of holes are
called "rollovers". In large faces the holes at the side

of the face for sq13r1n3 it up are called "side holes"

I” . I.
'9" bib

 

Th V or wod3o cut is one of the olficst and "till

i

m st connozly used. It caneieto 0;

so as to meet or psccticolly meet at t‘r ’r bot’om to form a

"U", two or more pairs of ?'3 1n perell cl plcocs to form

V

a wedge (Tiguro l). V-cu ts 1n dr1fts rc- be lor1sontol or

:0
ID
:0
:0
ID

—-
—
—-
_
—

—
—
—
—

DC
DC
DC
DC
'm::n
DC

\
/

(I:

(I:
G:
(E
O:
G:

FACE 55c3no~ FACE SECTION
"373160.11 V or ‘1}‘(.3-(.‘;,'jc Cut Ioublo V-cut 31-01.13.213
":‘a‘DJ,’ f:aot

T13. 1 ?13. 3
vertical, the tyTo selectca commonly being the or e allO"’n

the wider cn3lo to be drilled. - mzally bar Grill rountin s
are used for tl1c former t3 To and col din mount Inge for the
letter. In deeper drilled rounds or in very hard rock, cuts
may consist of double V's (Figure 8), the outer and shallower
V-cut being kn0”3 as the "bflxstcr or "baby” cut.
2:?CW" or "Too" Cut

Elie type of cut is s nocllfi ot1.on of th V cut.

It is located away from the center of the face and often the

holes are purposely drilled so that they do not meet. The

 

‘L

 

 

bottom draw cut illustrated (Figure 3) is most common, al¢

hough it may be located at the tOp or side of the round.

C'ZD CTJD
CID CZE
C21) C:

FHCE 55¢770N

--. 1 fi_
.1. 'l’aw b Kit
' ‘3 .I. q

:1”. U

1

Q ‘

7t is pertlcularly useful in small head1n3s, (less than 6 x

5'

6), where dr1llin3 must be done sLth unmounted h umer drills.
and wlcre due to lack of reoa it is difficult to drill a cut
in the center of the face.

"”Vranifi" Cut

 

n'

The cat union 1s probably next in pegularlty to
the V-cut is xuown as the "pyramid" or "diamond" cut. This
consists of three to six holes (Figures 4 & 5) drilled to
meet at a single apex near the center of the face. Th V-cut
or pyramid-cut rounds have an advanta3e over the too cute,
inasmuch as two or more charges are detonated t03cthcr. Th

added explosive makes it possible to break deeper craters.

I \ //
:' \\\ //
/ / \ \ / / \
/ \ / \\
é 1% c? \3
Fe c5 deer/0N FACE SECTION
$Lree Hole Pyramid Pour Hole Pyramid
Cu Cut
F1804 Fig.5

"CicLijan" or "BurnW_Cut

 

 

Tlfi s type of c at is known also under too names of

"i fl ’3

curn out", cornish" and "shatter" out. There are many
variations of thls cut, out all utilise the same principle.
Snlike the V or pyrarn 'd cuts 1Llc.h are desi nod to break
out a w 3,0 or cone of rock, the bur11 cut is inte11 Sued to
shatter or pulverizc a s all section of rock .Lich can be
scraped out if not already espellod by the blast, to leave
a re aghly cylinderical Opening a Hrs imately perpend1eular
to the face. fills out 0 Joe is ts of three or ‘13020 holes all
drilled in a closely spaced pattern(?13ure G) perpendicular
to the face a.d as z1early parallel to t%.o line of the drift

as possible. One or more of the.holes is not loaded, but

is present in the round to provide space into which others

.1 A.

can break. Also, at least one hole must be loaded to the
collar, since i: this is not gone, the collars o: th holes

may retail intact even thou3h the out may be broken inside,

‘55

 

 

 

 

 

 

 

o Q
o<>o 44
o l
E
\
\
it
ix
FACE 5ECTVON

Lichigan or L rn Cut

in which case there is seldom anything that can be done ex-
cept to drill and blast a new out. One disadvanta3o of this
type of cut in that it is always necessary to return and
make certain that the cvt is completely out before firing

the remainin3 holes.

-15-

m7""111 '1" ”7‘!" r "'.‘~"‘-a'~* ’ "1 r3311": «vm
la-J-OJ-RL ...: Zita“ .....aslefii U- ‘!.'\)'...o: 3 I‘LLv);
P"? ‘ ”P“. 7-,. 1. HT .v‘\Tl.r"1.?m
‘Ofi ‘u‘o 'I ‘- -3..4‘§J~J-.¢ .. bg“

Crater Theorz

 

Before any of the holes of a round are blasted
only one free face is caposcd in a headi.3. aft r tLe at
holes are broken the succeeding holes have pregrossively
more free faces up to tLe last lifters and back holes, which
have betVJeen two and tL; e free faces each to which to break.

According to the crater theory, a normal hole
drilled strai3ht in the leadinig vith one free face in homo-
geneous rock should, en blast-
ing, break out in a funne1-"na‘eo
elater the sides at an anrle of
£5 de3roes to LL 1300. $Lis 1%»

510 has been considered as being

 

the line of least resistance and

 

is she"m b" lines "bd" ed "be"

 

 

in Figure 7. ?Le theory presup-
..~ “ . ‘10 9 O
roses cnat Lo enfwlo ive enar3e a
is cnou3h to overcome the resis-
tance of the rock and is concen-
trated at point "b" at the bottom -*1
of the hole; in most rounds the Front Tlevatien
Wi 7
b-1130

explosive is distributed along

the bore. acteally, the crater broken by Lwla ti -n.:rj 81.H01 a
hole will be more alon3 line "do" and "cf", dependin a3 upon
tLe cLaracteristics of the rock and tLe speed and strength

of the explosive.

In blastin; out of the soll‘, th explos ive en-
counters reels tmzco uLiel is practi sally infinite in all
"rectlons c; {ccpt to"arl the surface. TLe size and sLapc
of the crater will be influenced by the amount of force re—

-‘

flected beck fronl tLe siees, wLicn in mlrn, depchs noon

tLe elasticity and compressibility of tLe rook. In rock
tLot taLes a relatively smaller amount of energy to over-
come th tensile stre213th in preportlen to that regaired to
sneer it, the aa3le of tLe crater will be miner. If the
rock Les e Ll L ten lle stren fltl, tl' ‘ze break will be were by
sLefin.’ n3, in leeLS case tLo crater will be larrowcr.

If the eznlosive is too slow or of insufficien

st;0z3oL, no rock, or nly a small amount at Le collhr of

--' - n 9‘ q - m ,--“- '9 ,~-,~-. nv-z-o- -_ an ~. .-~a.
tno Lulu, L ll ec broLeu. lf more eLelosive cl a L13L rate

(-1.

of detenntion L used 'Len is needed to bros” tLe line of

D

least re sietance, tLe rock may he broLcn beyond tLls line.

Should tLe 1 else of a round be drilled no deeper
tLan would allow the exylosive to break the rock only to
tLe tLeeroti cal 19. no of leest resistance, the advance per
roune coula be only one-half tLe sLortest dimension of the
face of the drift, which wsele not be satisfactory in nest
tiers.

Lxcept in very easy breaking rock, it is not prac-
ticable to bros: a round with holes drilled straight in the
face; tLerefere, tLe cut holes are drilled on an angle to
the face. By doing tLis, ‘Lc ane of least res- ster co is
not along tLe Cinectien of th bore Lolcs but throu3L tLe

solid rocl-; also more of the Cajlosive is beLind the rock

to be broken. Other things boin; equal az1d W1t11in practi-
ml 11m its, as tizo rosiot'“ce of the rock increases, more
Fitch must bo fiivon tho out holos in order that tLoy may be
broken to the bottom.
orezardinfi, for tlo t1.'no boinp , the occurrence
of plane of weacnoss 1n the rock, wL n a c- "“30 in a round
is detonated, it must Cotach too rock frozn the solid mass
and overcome tLe inertia of txe rock to be moved. The rock

1

is (3.1.1tached by crimifiuy, 5 08331113, 11111.: rwcrcomi r1 ‘ its ten-

silo strength. Loss enorgy is requlrod to overcxmo 2L0 ton—
silc strength of rock than to shear it. Crustin; requires

more force 121.1111 9." on .r.1113 ..

flnnos of TonPnons

 

Were it not for flame f weakness in tic rock,

U)
Q

the amount of oxylosivc of known :royulg 1ve oz1or3" required
to break give11 roLn. could probably be calculated by do»
to“ mnifl tne resista: co -.. tio rock to be overcome. It can
readily be conceived that th existence of Flares of weak-
ness in the rock 18 an important factor governing the qua
tity of e1:plosive required. For example, supyose that the
gjround in vhich a cri t round was drilled was cut up by
planes of weakness, making he rocn similar to car oiolly
piled bricks. In this case, tLe mly force req.Areo of the
explosion would be to overcome the inertia of the rock nd
the friction of tho blocks on each other. The L voss,
toughness, or mechanical strength of the rock would exert

no influence on the amount of energy required. Going to the

other extreme, to a face in which no planes of weakness oc-

u.‘ (I.

cur, the physical characteristics or tne rock would complete-
ly 3overn tno quantity ann quality of explosive required to
breal: a standard round. As the planes of weakness 3.11 the
rock decrease such enar'eterlstlcs of the rock as neriness,
,orosity, coxcsion, and probably other qualities
have an increasing influence upon the anount of explosive
required to break a round. The rock in meta mines almost
anarlaoly contains same planes of weakness aue to external
forces. Also, tne reek generally contains join in; planes.
Unere standard drift rounds are used in mines,
consid ration should be given to the planes of weakness or
slips in the rock in working out the standards. In a bedded
fonnltion standing at an an3lo, it is quite likely that the
best form of round For a Leading unnlng wit} the formation
would not be tno best type in a cross-cut. also, a round
,

in a drift on a vein with a well-defined free wall should
not be tne sane as in a nonalng in country rock. In the
first case, the round should be designed to break to tno
well, which would correspond to a major plane of weakness.

'Where standards are not used, some miners irill
their rounds to take advanta3e of planes of weakness, bu
the majority do not. At many mines the planes of weakness
have a definite relation to the lode, and each plane repre-
sents a series of slips extending througnout the formation

instead of Just beln: one slip.

*1 r- n 2 . s 1.
a assi1ieetlon 01 alsnes o: meanness

_
A

To be able to ascertain the effect of the planes

of weakness in rock under any jlvon set of conditions, a

o P

method or plln o? cl.ass fyeng the planes l5 no 3ess cry.

There Ls no uni‘versally tg-plicat lo plaza To to of :aluc,

a classticatLon rims to War lch out for eacL mile or dis-
tricz. a table is Tiven hire to illustrate the method used

9
O

at a western metal n no.

 

 

 

 

 

 

 

 

Planes
Gym ,
bol Hajor Hinor Joint 1.3
1 None Home to assista.zee.
2 Reno 4.3one Indisti riot assis-
tP-u ”(30 (311137.

3 fione 3" part, 1 way. 6" apart, 2 ways.

4 Hone 36" anart, 2 ways. 6" apart, 2 ways.

5 Home L" anart, 1 way. 6" apart, 2 may 5.

6 none 24" court, 1 way; 6" apart, 2 toys.

l at right angle.
7 Home 24" apart, 2 "a"s. 4" apart, 2 ways.
8 None as" apart, 1 'nay; 4" apart, 2 ways.
12" afart, 1 way.

9 None ‘ 3" apart, 2 ways. 4" apart, 8 ways.
10 l with 6:1; t. 1“" ayart, 2 ways. 4" apart, 2 ways.
ll 2 with dril ft 12" apart, 3 ways. 4" apart, 2 ways.

aunt {3133...}: _O
12 2 with url it 8" apart, 2 ways.‘ 4" apart, 2 ways.
ssLs ”n5.

 

Cla:3sif.1cation of Tlanes of toaLness in Rock,
Lisbee (Lriz.) Iis trict
S‘asle 1.

In the table the term "major" is used to designate
fault planes or well-defined fractures along ezlch tncrc is
no adhesion of the rock on eithaz side. These ms or flanes
are 50 nerally identified by talc or slick aslees.

The term"ninor"1s applied to well-defined bedding
planes or fractures along which the rock has a tend ncy to
break on blasting. To be classed as "ainor" the planes of

weakness mxzst be extensive enou:h to influence ti;e break.

The term "jointing" refers to the jointing planes

in tho rock. Ticse planes assist the explosive in crushing
the rock, as in blastinf the fiwst cut holes. Incision

groupeo n tLis class.

fractires also are

7

This classificat;on considers planes of wssgness
only in one or two dimensions. Llero slips occur in all
tgrce dimensions the rock is ordinarily called "blocky" and
is correspondingly easi or to break. At mines where the rock
is blochy a different table of classification would be no-
cossary.

The rock is classified cy inspect s; the face
tops , and sides of the drift at the face. Slips :srsllol
to the drift ere shown in the face; cros s all rs are estima-
ted by those appearing in the drift for the some distance
back of the face as the depth of the round. Cf Covi.s, the
number and izlnc of cross slips can not always be accurately
deterrinedi this monncr, but in a large rsjority of cases
a close srrrozirstf.on can be made.

The planes of veekness in a face will very seldom
conform exactly with an? or 0 class, but ju’;ment nxzst be
used in putting the face in the right colunn. If alteration
has occurred along the minor slips, the rock "111 be easier
breaking, and the face no st be :It in a class requir2_ng less

eXplosive. If recementstion has taken place, t: e influence
of tLe planes of weakness will be reduced and a Lifiher classi-
fication must be used. Also, in some cases planes of weak-
ness in the rock will not affect the brook favorably or may

influence it adversely. This generally can {)9 dedlced from

A.

an inspection of the face. Cross slips in the rock may re-
duce the break of the round. A well-defined slip of a foot
from the face in a four foot round would probably limit the
break to three feet. The same slip at the end of the holes
would probably increase the break. Soft places in the rock
and other fractures may effect the advantage of planes of
weakness in some cases.
gheory in Cesign of Round;

Rounds should be so designed that each hole can
break as nearly as possible to the lines of least resistance.
Cut holes should be drilled to break a cavity in the center
of the face. Each succeeding hole should be placed to take
full advantage of the cavity made by preceding ones. The
side holes, when blasted next after the center cuts, break
out to the first crater by shearing and overcoming he ten-
sile strength and shear or crush the rock out to the line
of the heading. Equivalent holes above or below have an ad-
vantage in that less crushing is required, as there is a
larger area in the face to which they can break.

Theoretically, it appears that in breaking rounds
a wedge-shaped slot with a length at the face equal to the
shortest dimension of the heading should be broken in the
middle of the drift in the line of the largest dimension.
hext a cross slot should be blasted out the full width across
the middle in the other direction. The succeeding holes,
which are mainly slabbing ones, should be placed to break

into the Opening already made. These succeeding holes ShOJld

also be so arranged that the lines of least resistance from
the explosive are as nearly the same as practicable in all
directions in which the break is required. To secure this
in some of the holes, a special distribution of the explo-
sive in a hole will occasionally be necessary.

The force of the detonation of previous holes fre-
quently collapses some of the.holes in a round, particularly
the lifters, as was found in blasting tests where rounds
were shot one hole at a time. This is more frequent in over-
loaded rounds or in plastic rock. Also, the rock may move
along a plane of weakness and partly collapse a hole. Fuse
may be cut off or pinched by this ground movement and cause
misfires. Therefore, rounds should be designed with this
in mind and the holes placed to reduce this hazard to a mini-
mum o

Fevelopment of [rift Rounds

In the early days of mining, when holes were drilled
by hand, each.hole was placed to take advantage of the planes
of weakness in the rock, the contour of the face, or other
features that would assist in blasting the ground. Explo-
sives were used.more effectively, both because each hole was
drilled to the best advantage and because shorter rounds
were shot. The men soon learned by eXperience the best me-
thod of blasting each face, and they could generally ascer-
tain the rock broken by each.hole.

With the advent of air drills, longer rounds were

drilled. The first machine rounds drilled.wero patterned

after the hand-steel rounds, except that holes with a down-
ward angle were substituted for holes pointing upward. Flat
or upward-inclined holes were difficult to drill with the
old piston machines, which were the first type to be used
in metal mines. The modern Loyncr-type machine, which forces
.air and water to the cutting edge of the bit through hollow
steel, cuts faster where the removal of drilling cuttings
is assisted by gravity. however, the drilling speed of many
machines new on the market is so fast that drilling upward~
pointing moles gives but little material advantage.

The first type of round drilled with the piston
inachine is shown in Figure 8. Practically the same round

is now being drilled, using a crossbar, at some mines, ex-

 

r———3
1——

 

 

 

 

 

Toe Cut Round Prillod with
Piston hachines
cept that the two back holes are generally drilled at an up-
ward rather than a downward angle. As most drifts are wider
at the bottom than at the top, the cut holes have a better

chance to break when drilled downward.

To take advantage of the faster drilling speed of
upward-inclined holes with the Leynor machines, a round as
shown in Figure 9, is drilled at some mines where the broken
rock is removed previous to drilling in the face. Under fa-

vorable conditions, after blasting the out holes 1, 2 and 3,

 

 

 

lSoHole Round.with Upward Toe Cut
Drilled with.Leyner Typo Drill

a wedge-shaped section of the face will be removed, as shown
in the side elevation by the lines a, b, c. The other holes
have the Openings made by the first ones to which to break.
When the cut holes break well, the subsequent holes normally
break to the bottom.witheut difficulty.

The introduction of faster drilling model: made
possible the drilling or deeper rounds in a shift, but it
was found that the full depth of the longer toe-cut round:
was rarely broken except under very favorable conditions.

As the depth of round that can be broken depends largely up-

on th execution done by the cut holes, many experiments were

made to develop forms of out holes that would break'more
ground than the too out. As a result of these investiga-
tions, the V—cut and pyramid-cut rounds with a number of
variations were develOped. In a pyramid-cut round three or
.four or even more holes are drilled to bottom together or
close enougn together that they will detonate simultaneous-

ly. A four-hole pyramid-cut round is shown in ?i;ure 10.

l

 

 

 

 

   
   
  

 

[:i‘ e 17' ’
f“ * ‘
9s
to” Q\\\ v I I”? _
\ I

 

i

7“—

 

 

N
c:a z,” ‘1‘ as:
6’ I! ‘0
U ,
o
\’I" %c 9‘“

16-Hole Round with 4-3019 Pyramid Cut

 

In ground particularly difficult to break or in
deep rounds, advantage is sometimes gained by drilling either
a short single hole or a pair of holes to relieve the main
cut holes of a round, as shown in Figure ll.

It is very important to know how the holes of a
round break in choosing he best form of round for any par-
ticular class of ground. Quite frequently improvement in
placing the holes and in the distribution of the explosive
is suggested by observing the results of blasting rounds a

hole at a time.

 

 

 

 

 

 

Short Cut holes to Relieve Burden of hain Cuts

Depth of Bounds: The drilling and the blasting
of rounds are closely related and must be considered together
in developing methods for breaking rook. Several factors
govern the number or.holes and the amount or explosive re-
quired for any particular round. At most places, a low cost
per foot is desired for all headings. Sometimes speed is
more desirable than low cost. in which case the most econo-
mical manner of performing all Operations can not be carried
out. I

Experience has sheen that in.msny instances. the
most economical round to drill in a drift is one that can
be finished and blasted in one shift: it is also desirable
to break only as much material as can be removed in the
next shift to keep a cycle of operations. Sometimes in large
headings or in ground that is easily broken. it is possible
in one shift to drill a round that will break more rock than

can be shoveled out in the next unless a mechanical loader
is used. In hard or medium ground, however, the shevelers
can ordinarily remove as much rock in one shift as can be
broken in one blast on the preceding shift. At most places
blasting in drifts is done only at the end of a shift, thus
avoiding the interruption of other operations an the pollu-
tion of the nine atmosphere.

Vhere blasting can be done at any time or where
Operations are continuous, as deep a round as can be broken
may be drilled. At some places such deep rounds are drilled
that the out holes must be re-blasted several times to get
a full break.

The depth to WJlGh a round can be broken depends
upon the following factors, which are more or less related
to each other:

1. Planes of weakness of the rock.

2. Physical characteristics of the rock.

3. Kind, grade, and quantity of explosive.

4. Distribution of explosive in holes of round.

5. number of holes in a round.

6. Cross section of heading.

7. Form of round. ,

8. Diameter of drill holes.

In blasting, the rock must be taken as it comes.
The planes of weakness constitute the most important factor
concerning the rock that limits the depth to which a round
can be blasted. The physical characteristics of the rock
are important but are subordinate to the planes of weakness.

The depth to which a round can be broken depends

obviously upon the explosive used and its distribution in

the holes. These matters will be discussed later.

Ehe number of holes in a round dot-rhinos the dis-
tribution of explosive in the face and the quantity that can
be loaded. “requently the number of holes dri led depends
upon the time available. If th ground looks difficult to
break and he has time, he miner may drill an extra hole;
otherwise he will load heavier those already drilled.

fhe size of the Leading determines the angle that
the cut holes can be drilled, which in turn, affects the
depth to which a round can be broken. The depth and angle
of a cut hole is limited by the distance from the collar of
the hole to the li: ts of the drift on the line of the hole,
a distance that dust canal or very nearly equal the length
of the longest steel used. In long holes, the bit of the
last drill will be one-fourth to one-half inch smaller than
the diameter of the hole at the cellar, which allows the
steel to be pushed into the hole even if slightly out of
line at the start. The most economical height of drift in
development work may depend upon the cost of disposing of

"91

the blasted.material. where the waste is desired for filling
in stepes or where a short tran.te a dump is available, a
drift eight feet high may cost less to run than one only
seven feet high. If disposal of waste is costly, a higher
blasting cost due to a lower back may give a lower cost per
foot advance.

The form of round is important, nd under some
conditions a lonjer advance can be made with one form of

round than with another. In hard ground, the dist nee possi-

.s o . ‘ .9 9 . . a . 1 ,.
blo to bros: mw.y toponu on tno inelinnt on oi the out neles.
"" ~‘.'.’ ~‘. , '- fl “ ‘M n . ., r I'r 9 ' 1‘ “" ‘ L." ‘ "
u-t4 inc 3,: oi tno heading reunining one sane, one noogor

the round he loss angle can be given the cut holes.

There has been a tendency to reduce the diameter
of bore holes to lower drilling costs. tithin reasonable
lim11ts it costs less to drill holes of small diameter. How-
ever, in the s2uallw (‘iamotor holes, less oxylosivo can be
used. This disad an a; in some cases can be compensated
for by uain mg a hijhor *rade czplosiv 1e that will contain th
sane breaking energy in a smaller compass. The diameter of.
the holes should not be rcdue d to loss than one inch, as
below this diameter the eXplosive may not detonate at its
high rate. The drilloeteol stock used at most nines pre-
vents holes of smaller diameter being drilled.

As the time taken to set up and take down the drills
is the same, the cost per foot of drilling holes in deep
rounds is loss than in short ones, other conditions remain-
ing the same.

The cost of drilling is the major item in advan-
cing a drift. The cost of explosive is about oneéthird of
the cost of drifting; therefore, it would appear economical
to blast as long rounds as could be practically drilled and
broken.

Standard Rounds: Certain kinds of rounds seem to
be favored over others in some districts, irrespective of
the kind or nature of the rock or improvements in exnloeives.

Miners are conservative by nature, and once they have learned

...‘Rfi—

to drill any particular form of round it is difficult to
cnange tneir says. At sane mines a form of round favored

by tLo experinten dent or fore.uan is used, wL reas anotLer

fo "aimi;ht be better suited for the conditions existing tLere.

HLere tLe individual miners are sLilled in plac fig
tLe holes of a round and Lave no inherent prejudice, the
best results can be obtained by leaving tLem free to drill

ed tlast the holes to take advantage of all favorable con-
ditions in each round. ‘any such sLilled miners are still
work ng in the a Les, bit tLe proportion of morrncn uLo do
not Lave an adequate kno ledge of tLe effec of the ex;lo-
sive is so large tLat where tLe form of round drilled is

oft entirely with tLe miners, the best results tLrougLout
tLe mine are not always obtained. Under such conditions a
standard round worked out for average conditions for each
type of ground would seem desirable.

Instances have occurred wLere green men taught to
drill rounds by a standard Lave made better progress than
diners whose experience has been gained elsewhere, and who,
influenced by t- zeir prefers encos, insist on drillin;3 anodi-
fication of the standard round.

Haisin;§?ounds

Raises are small passages driven from a lower
level to a higher level. They may vary in inclination from
vertical to nearly horizontal and all holes will be pointing
upward. It is necessary to build a platform for the men to

drill from arid ordinarily, ti.is platform is left in place

during the shooting to catch the ore and control its dss-
cent to the masking level. Figure 12 shows a typical raise
round in moderately hard rock. The method for blasting
this type of round will be discussed later.

 

 

 

 

 

 

 

 

 

\\ s “\\‘I

 

\\\\\~ \\\\\\l

New

  

 

Vertical Raiss Hound
Fig. 12
gigging Rounds
Shafts and vinsos sro pssssgsrsys sunk from ens

level to s loser lsvol. Figure 13 shows s satisfactory typo
of shaft round for small shafts. It docs not utilize tbs
usual sedge or cone-typo out but makes use of a principle
known as a “sumping” cut. in uhich.cseh round forms a sump

to collect the water so that it can be pumped out easily

and leave s relatively dry bench on which the men can do
their drilling. This type of round is almost a necessity

in very not work.

 

 

 

Small Shaft hound with.Sumping Cut

One or the greatest items of expense in shaft

sinking is the drilling which normally cannot be carried

on until all of the rock from.the previous blast has been
mucked out. Hemmer drills are usually employed as.they are
much.mcre flexible and rapid than arrangements for mounting
the drills on cross bars. The number of drills that can be
used depends. of course. upon the size of the shaft. The
holes should never bottom less than l 1/!“ in diameter and
preferably larger in order to allow the placing or more ex-
plosive in the toe of the hole where it is needed. The most
economical size of dynamite cartridge for hard rock is usu-

ally l 1/! x 8” and this will require a hole bottoming from

1 3/8 to 1 1/2" in diameter. As in the case of tunnels,
both the diameter of the shaft and the type of rock govern
the number or holes necessary to pull the round.

Figure 14 shows a rinse round using a draw out.
This type of cut is very practical if the wines happens to

run along s vein or slip. If there is a free parting at

 

Wines Round Using Draw Cut
Fig. 1‘

this point it is usually unnecessary to drill the holes
along the bottom, although it is advisable to put in one
or the loser corner holes and shoot it last in order to

furnish a sump.

O“? Y'P‘Vr‘ Iaxhv‘Ifi‘y-sfiY
liaéIL-Llelhil \I ll.) VIA-bline‘k

Three methods of drilling rounds are used in
American metal mines: (1) by drills from mountings set up
at the face, (2) by means of uimounted drills held in the
hands of the operator, (3) by hand power. The last method

(I

oi drilling is seldom used in present-day mining and will
not be discussed in this paper.

Hammer drills operated by steam or compressed air
have largely replaced the older piston-type drills in metal
mining. These drills can be operated either wet or dry.

The Leynor drill is an Ancric n drill especially adapted
for use in rock where a water jet enables a bit to cut fas-
ter. The Leyner drill has a hollow drill rod through which
the compressed air forces the water which escapes through
holes near the bit. The compressed air is the principal
agent in cleaning the hole, the water laying h dust and
assisting in the cleaning. The drill steel is not fastened
to the drill piston, and is not churned up and down in the
hole, but is struck by the piston, which also rotates the
drill bit automatically.

Sinker Frill

This drill, which is usually Operated by compressed
air, is most serviceable for drilling holes u: to 10 foot in
defith, and is adaptable for use in drill as here holes for
shafts. The drill is comparatively light and easily carried.
The required air is furnished by a portable comyrcssor when

a stationary compressor outfit is not convenient.

 

 

Sinker $rill
IllUSela

 

Sinker Frill Oneratinn in Shaft
Illu8.1b

 

Lgigter Srilla

A slight modification of the mounting permits the.
hammer or sinker drill to be mounted on a vertical column
or horizontal bar in a drift or cross-cut. This permits ra-
pid drilling, and is much used in tunneling and mining opera-
tions. than the vertical column is used the drilling machine
is mounted on a cross arm on the column. This arrangement
allows latitude in starting holes in a face, as the drill
can be used in any position desired. Holes are generally
drilled in sequence, beginning at the top of the face. The
broken rock from the previous round.must be removed or thrown
back from the face to allow the column to be set up. When
rounds are blasted on each shift, extra work is required to
shovel back the broken material to set up the column. Illus-
tration 2a shows a vet drifter mounted on a vertical column.

with the arrangement of water tank and hoses.

 

 

 

 

 

 

 

 

/
‘ Zl<r

' /~

Wet Drifter rounted on Vertical Folumn
with Arrangement of Later Tank e hoses
I 11“. o 23

At most places where drilling must be started be-
fore the broken rock is removed, crossbars are used. host
of the holes can be drilled from a set-up at the upper part
of the drift above the broken material. By the time these
holes are drilled the rock is generally removed, then the
bar is torn down and set up again at the bottom to drill the
lifters and at some places, other holes of the round. Illus-
tration 2b shows the drifter mounted on a horizontal cross-

bar.

 

Drifter haunted on Horizontal Crossbar
’ Illua. 2b

Stoper Drill;

These are special hammer drills used for overhead
drilling, as in raising and in overhand atoping. Stepers
require no separate mounting since they stand on a telesco-
ping air leg. ?he air leg not only serves as support but
is also the feed mechanism. Illustration 3 shows a stoper

in operation on a vertical raising round.

 

Steper in Operation on Vertical Raising Round
Illus. 3
Drill Carriage;

A In recent years, tunneling operations have made
good use of the drill carriage of “Jumbo” mounting. The
drill mounting consists of a heavy framework for carrying
the columns, arms, and bars for mounting two or more drills.
Up to thirty-five drills have been mounted on the largest
carriage. The earriafie also comprises platforms for the
drillers to stand on, usually designed to drop to the side
when not in use; facilities for carrying drill steel, bits,
and tools: manifolds attached to the main air and water lines

and providing outlets for each drill; and finally, headlight

or flood 11,3112; to 11". 1:11.») ‘5 '. .1 i". I” so. ' i- -'.J. "9;?-

-‘.
.J

- ‘. inwfifit. , 1., . 2. . _ . \ ,~ .
ridges nay be ,‘-it o; in“:H3 p» Pix *1 rain” ;P v‘ S'i--

tral“.:11n.: Guy :1” - L-IA-r-‘L‘ H": '1...\~ ‘13 , :It. 1'1, - - it v . - , ' ‘y : _-‘ ‘\ ‘

\\ //'/q;\/ \\ '

I

{\\\\ /\\ . 'x'

 

_. fi__“

r- Arr-"era r:— N: I"‘~'.r'?vir‘
uLn..)J..L1.st LnIL'I‘ dumb-a1 u

Af er a round has bee: drilled, the sludge made
by the cuttin3s and any drilling water are blown out of the
holes by means of confiressed air through a blowyipo. Th
blast in3 supplies are then broujht up to t11e face, pri.sers
made, and the round loaded and blasted.

?rimers
A primer is a cartrid3e of exrlos ive with some

means of firin3 it atttehed. It is placed in the bore hole
alon3 with he remainder of the eiarge and when fired, ex-
plodes the latter. Eoth the method of makin; n. primers and
the location of the primer cartrid3e in the loaded bore holes
vary with the kind of explosive used, the type of i3niter or
detonator used, and with certain conditions of blasting.
In blastin3 dri t rounds tne primer cartrid3s is 3enerally
of the same explosive used for the main charge, but occa-
sionally a different kind or grade xill be us ed. In metal
mines, fuzo and detonators (caps) are mainly used as the de-
tonn tin3 cevice for blast? n3 d ’ft ruo~nde. Tet drifts are
frequently blasted wit h elec‘ric delay detonators, and at a
few places, all drift rounds are blasted in this ranner.
The number of metal miners familiar with electric blasting
is relatively Shall, and agpareetly the lack of trained men
is one of the main reasons why tLis method 3 sheet :3 rounds
is not more 3ene rally used.

rinei°s shou d be carefully male so that the; satis-

fy'the following cenditioes:

(1) That the igniter or detonator cannot be pulled out of
the primer cartridge.

(2) That the igniter or dctonntor be in the safest and most
effective position in the primer cartrid3e.

‘

(3) That the fuse or the wires of electric firing devices
are not subject to harmful strains.

(4) That the primer is taterproof if necessary.

(5) Tint the whole primer assembly can be loaded safely,
easily, and in the preferred position in the charge.

Copying Pugg: Preliminary operations include cut-

ing the fuse and crizping on the caps. This work should
be done in a dry place and care taken that all fuse for
specific purposes is cut accurately to length. The length
of the fuze out should be sufficient to reach from the pri-
mer in the bore hole to the collar plus some additional
length outside the hole. In all blasting, the minimum len3th
should be sufficient to allow the blaster en ugh time to
reach_a place of safety after lighting the fuse plus what
additional length is required for trimming. Under no cir-
cumstances should less than two feet of fuze be used. ile
fuse should be cut squarely across with a sharp instrument.
The capping of the fuse with a detonator should be done in
such a manner that the explosive composition of the detona-
tor fits snugly against the end of the fuse. (See Figure 15)
Also, the detonator should be securely crimpod on the fuse
in order that the fuse will not be pulled away from he do-
tonator during loading or by the concussion of the preceding

shots.

~42-

CAPSHELL GAP {- FUZE

 

 

EX‘PLOSIVE POWDER CORE
CHHRGE

Po OR C u 1' T/Ne
CAP SHELL N0 GAP (- Fuz E
Ex PLOE SIVE CHARGE 3mm CORE

PROPER INSERTION

 

 

Fig. 15

Strength of fetonators: The Bureau of mines re-

 

commends the use of No. 8 detonators, No. 8 electric deto-
nators, or no. 8 electric delay detonators for all blasting
in metal mines. A strong detonater imparts a greater ini-
tial impulse to the explosive, which theoretically brings
the explosive wave in the charge to full speed.mere quick-
ly and thereby increases the effectiveness of the blast.
Gelatin dynamites are relatively insensitive to detonation
and become more insensitive with age. Fewer misfires should
occur when strong detonators are used.

Handling Detenatore: Capped fuse should be sent
underground in closed rigid containers and taken to detona-
tor lockers, which should be at least fifty feet from the
powder magazines. Capped fuze should be issued to minors
separately from the explosive and carried to the working

faces in separate bags. Electric and electric delay deto-

nators should be handled in the same manner.

Primers with Fuse and hetenaters: Considerable
variation exists in the method of placing the detenator in
the cartridge; and.many experienced men, including both mi-
ners and bosses, have different and decided ideas of how
the work should be done. In making a primer, the first eon-
sideratien is that it can be loaded safely, the second that
when the primer is loaded the detonator will be firmly an-
chored in the primer cartridge, and the third that there
shall be no sharp turns or kinks in the fuse that would be
likely to pinch the powder core of the fuse.

There are at least four methods in general use
for making primers with fuse and detonators as illustrated
in Figure 16. From the standpoint of effectiveness and
safety, Primer "A" is probably the best as it is difficult
to pull out and it takes advantage of the fact that the
greatest force of a blasting cap issues from the base in the
direction of the longitudinal axis of the cap. Primer "h”
is practically as good both from the standpoint of effec-
tiveness and safety. The methods shown in "0-3" and "D"
are very poor as the sharp bends caused by lacing may crack
the waterproofing so badly that moisture present in a bore
hole or in the stemming will cause a misfire. Tue poorest
primer is one in which the base of the cap is near the out-
side of the cartridge, "0-1" and "0-2", where it is likely
to break through if tamped hard and cause a premature explo-

$10!).

-44-

RECOMMENDED

FUZE TIED wm-I STRING
fl CENTER PRIMING 8 SIDE PRIMING

NOT Recon/verve: O

 

 

 

 

 

 

 

\::\ 0,5 \:\ [fix

0'! POOR CAP POSITION C-z DANGEROUS POSITION
': \ \z’tzg , M53"- :1\)

C-3 FUSE STRAINED D HALF HITCHED FUZE

Primers with Electric Felay Fetenators: There
are numerous methods of priming dynamite cartridges with
electric blasting caps but the preferred methods (Figure 17)
involve several fundamental principles: (1) The detonator
should be in the center of the section of the cartridge and
parallel to the long axis of the cartridge. (2) The wires
should be attached so that they will not slip off or permit
the cap to be pulled out of the cartridge; so that the pri-
mer can be loaded with either and foremost and drawn out of
the hole, if necessary: and so that there are no sharp kinks,
knots, or overlaps in the wires that might cause the wires

to break or to out into each other through the insulation

and short circuit. In Figure 17, Cartridges A and B illus-
trate the recommended methods of making up a primer with
small diameter cartridge and electric blasting cap. Car-
tridge C illustrates the method which is most frequently

practiced although not recommended.

 

 

 

 

 

METHOD H METHODB ME THOD C

Position of Primer

Theoretically, the ideal method of primiig is with
the primer near the outer end of the hole and the detonator
pointing toward the back. Hewever, in multiple shots or
rotation firing, it has been observed that almost invariably
the fuse of all holes except the lifters are sheared off
even with the collars of the holes by the blast of the first
cut hole. Therefore, it is necessary that the primer should
be in such a position that the fuse will not be cut off at
any point before the train of fire has passed it. Obviously
each primer should be far enough below the collar or the hole

that the train of fire in the fuse is within the solid rock

before the first out hole explodes. Figure lB-A shows the
recommended method for priming dynamite charges in dry holes,

18-3 for firing in wet holes.

F uze /CHHR6E \ FUZE /CHHRGE
.Mfifififizmwmfifiiififiiifii"7431Iigy?,«”fififififififififiiifiiiifiifi§ifII§!/ """"
7/ /’ ‘.' V , V /
5L HST/N6 cap BLAST/Ne mp
STEMM/NG PRIMER STEMM/Nc PRIMER
A B

Fig. 13

To protect the detonator, one cartridge is gen-
erally placed in the drill hole and is tamped well before
the primer is loaded. This should always be done when the
fuse is turned back along the primer cartridge.

When electric blasting caps are used the ideal
method of priming charges, with the primer near the outer
end of the charge and the cap pointing toward the back, can
nearly always be used. This applies equally to single shots
and.multiple and rotation firing. There is no danger from
cut-offs in the latter instances because the electric blas-
ting caps fire together and always are the first to fire in
rotation rounds.

Tagging

Tests have been made which indicated that in hard

rock there is an advantage in having as great a loading den-

sity of the explosive as it is possible to obtain by ordinf

-47-

ary methods. Granting the advantage of a high density, the
charges should be tamped to fill completely the section of
the drill hole. The general practice is to slit the paper
covers of all cartridges except the primers before placing
the eXplosive in the bore hole, which allows he cartridge
to "mushrOOm" when pressure is exerted against it.

In tamping a hard explosive, fuze or the legs of
electric delay detonators may be kinked enough to cause a
misfirez. herefore, care should be taken in loading the car-
tridge next to the primer not to damage the primer or cause
a kink in the fuze or the wires of an electric detonator at
the outer end of the primer cartridge.

Enough time should always be allowed for charging
a round. hurried or careless work causes many misfires and
some premature explosions. The explosive can not act to
the best advantage if the men doing the work do not take
time to prepare and temp the charges preperly.

Stemming

Stemming may be defined as an inert material placed
in the outer portion of a bore bole to confine the harge of
explosive. In some localities, it is called "tanping" by
the miners. Numerous tests have shown conclusively that
stemming increases the efficiency of eXplosives in blasting
rounds in underground metal mines in all places except in
very soft rock.

Mine superintendents generally concede that the

use of stemming saves explosive in blasting, and at a few

mines a constant effort is made to see that it is used through-
out the workings. However, at most places it is considered
that the effort necessary to enforce the use of stemming costs
more than the saving effected by its use.

Hoist clay appears to be the best stemming materi- ‘
al, but damp sand is nearly as good. Coarse or a gular sten-
ming should not be used, as there is danger of damaging the
fuze or wires of electric detonators. Most mining campanies
use dry tailings sand from concentrators, as the cartridges
are more easily made by hand with this material. Empty pow-
der cases are packed with the paper shells with the Open and
upward. The sand is then poured into the shells, after which
it is moist ned, and then the opened ends of the shells are
closed by hand. Clay cartridges are cheaply made with a
reel ding machine .

The main valid objection to the use of stemming
is that it is harder to take care of a misfire with stemming
in the hole. iowever, most missed.holes can be reblasted
by placing a new primer in the hole on tOp of the stemming.
Of the explosive in the hole is too insensitive for this,
most of the stemming can be removed without undue danger.

Firing Holes With Fuss a tetonator

The final act in blasting is the actual firing of
the loaded charges. With each method of firing some prepara-
tion is required, such as trimming fuse, connecting up and
testing electric circuits, and the like.

Seven-foot fuse are generally used for blasting

..A (3....

ordinary drift rounds. To get the proper sequence of firing,
a piece 12 to 18 inches long is ordinarily cut from the fuse
in the first hole to be shot and a section one-half to one
inch less than that for the preceding hole is cut from each
succeeding fuze, except that in the last lifter which is

not cut. Safety fuse is made in two distinct speed ranges,
namely, that which burns at approximately 40 seconds per
foot and approximately 30 seconds per foot. The manufactur-
ers hold the variations to 10 per cent either way at the
time of manufacture.

Holes are lit in the same rotation as the firing
sequence, and.whcre no ‘ifficulty is experienced the time
required to light as li-hole drift round with an open-flame
lamp is three-fourths to one and one-fourth minutes.

In most rounds, no advantage is obtained by having
a certain group of holes fire before others. Thus, after
the cut holes fire, it is immaterial whether the breast holes
or shimmers fire next. Also, in most rounds either one of
a pair of side holes could detonate before the other with-
out influencing tho break of the round. Such holes are
grouped and shot with the same delays in firing electrical-
ly. however, this practice is not generally followed when
used fuse and detonator as is shown in Figure 19, hich il-
lustrates the rotation firing of the holes.

In a ld-hole round drilled as in figure 19, the
holes could be grouped in this manner: (1) 2 center cuts;
(3) 4 side V cuts; (3) center breast and center skimmer; (4)

2 side breasts and 2 side shimmers: (5) back hole and center

3"" ._

3‘. ‘-

l“

 

 

 

lifter; and (6) 2 side lifters.

 

 

 

 

 

 

 

[—4'
——+
..-_::-' 1r
‘
C_ l
:-—=:--.-—
:~- ‘
E ‘~:~i
\ “
\\ .
\\
\\
\\
\\
\\ \
\>\‘
I " m
,’/|
/ /
I /
I
L"/
I ’4
’
”;”‘
2’,” I

 

 

l6-Hole Round, Figures Indicate
'the Rotation of Firing Holes
Fig. 19

Attention should be called here to a very im-
portant precaution in the firing of blasts -- the safe-
guarding of all persons including those working directly
on the blast, and those engaged in other work n the vi-
cinity. Two - and only two - men should be present while
a drift round is being lit. If one man loses his.li;ht,
the second is there to give him another.

Wet Holes: When wet holes are to_be shot with
fuse, they should be lit as soon as possible after loading.
Even with.the best protection, misfires are likely to occur
if wet holes are left standing over fifteen minutes. In
wet work most misfires are caused by the failure to make a

waterproof connection between the detonator and fuze.'

Watergroefing Raga: host fuse used in metal nines

 

will withstand water for a considerable time. However, de-

tonators are made insensitive by small amounts of moisture
and will fail to fire if wet. Therefore, in blasting in
wet places the capped end of the fuze is treated with some
waterproofing material. Various preparations are used.
Grease and candle taller are the old stand-bye used by miners
when other material is not available. P.& B. paint No. l
is successfully used at many places. The fuze companies re-
commend that only cap-sealing compounds made for the speci-
fic purpose be used for waterproofing the crimp Joint be-
tween the detonator and the fuzo. Waterproofing compounds
should not contain anything, such as gasoline, that will
tend to soften or penetrate the waterproofing coats of the
fuse. Some materials used for sealing the connection may
have excellent waterproofing qualities, but if they attack
the fuze they will defeat the purpose for which they are in-
tended.
Firing_fioles with Electric Delay Detonaters

There has been a large amount of material written
as to the relative values of blasting with electric delay
detonators over the use of safety fuse. A predominance of
the blasting in metal mines is still being done with safety
fuse even though it seems apparent that electricity is as
efficient and safer, although the cost will run slightly
higher. In sinking and raising, electric detonators have
come into almost exclusive use as it is necessary to give
the miners plenty of time to retreat to safety before the

blast is fired.

-50.-

In the larger mines electric current from lighting
or other circuits is generally available for firing electric
detonators, but occasionally a blasting machine will be re-
quired. When there is ample current, the detonators of a
round should be connected in multiple, but where it is neces-
sary to use a portable blasting machine, it is best to con-
nect the holes in series. There is less likelihood of mis-
fires from leakage of current or short-circuiting when a
high voltage is used. When wiring in multiple, the legs of
the individual detonators should be long enough to reach to
the bus wires without splicing. The leg wires for a 6~foot
round in a 6 z 7 foot face should be 10 feet long. Zach de-
tonator should be tested with a galvanometer before and af-
ter loading to insure that no circuits are broken. The ends
of the two leg wires of each detonator should be twisted to-
gether before the detonators are taken underground to pre-
vent possible premature explosion by stray electric currents.
After the round is loaded the bus wires, which should con-
sist of uninsulated copper wire of about No. 16 B.& S. gage,
are strung across the face and fastened to two wooden plugs
or stakes. Care should be taken that the bus wires do not
touch each other. One wire of each detonator is attached
to one bus wire and the other wire to the Opposite bus wire.
hash wire should be attached individually and care taken
that connections are well made and that no short circuits
occur.

The temporary firing line, which should consist

of 30. 14 lead wire, Ho. 13 annunciator wire, or Ho. 20 con-
necting wire, should then be connected to the bus wires and
the work proceed away from the face. The ends of the per-
manent blasting lin should be touched together to make sure
they carry no current before the connections to the tempo-
rary firing line are made. Two single wires rather than a
duplex lead wire are to be preferred. The use of single lead
wires prevents line losses of current and also makes the lo-
cation and repairs of breaks simpler. The round should be
fired through a safety switch, which.must be kept locked in
an Open position; the minor in charge of the blasting should
have the only key.

Delay electric blasting caps are similar to regu-
lar electric blasting caps, except that a delay element is
inserted between the electrical firing element and the de-
tonating charges. They are manufactured in standard periods

(I

oi delay. For instance, Dupont Delay Electric Blasting Caps
are manufactured in ten standard periods of delay, ranging
in numbers from a l-delay to lO-delay. The time interval
of delay for the first period is approximately one second
and the time intervals increase gradually up to approximate-
ly 2% seconds between the ninth and tenth periods. Figure 20
illustrates the use of electric delay detonators in a typi-
cal drift round at the Cliffs Shaft mine, Ishpcming, fiichi-
gen.

The central hole in the cut section is fired with

a regular electric detonator or a #0 delay. The remaining

cut holes ar fired with $1 delays; the bran ast holes wit};

5'5 delays; he side breastS, side wanna-ms, bacl’ 0105' and

lifters are all fired with a 35 delay.

 

 

00
O
5553
00
0333
57°95?
9°00”
! 3’ ’ J!

on
on
on
05.

 

 

8!

 

20-Hole Round Cliffs Sh- ft Lino, Hichigan.
Numbers Indicate Llectric Delay Detonators

hleetric blastin- has a trio-fold advantage over

53"

fuze and detonators in wet ifts; there is less likelihood

of misfires occurrinr caused by moisture, and the c m13er is
eliminated of men staying too long at a face while lighting
wet fuse. hangfiros are less frequent with electric blas-
ting, and men can take plenty of time to reach a place of
safety before firing a round. The pose ibili V? of misfires
from fuse being out by previous shots is eliminated, and the
rotation of firing is suror with electric blasting.
an ant of ixplosive Per,holc

The die tributien of the explosive in the holes of

a round is important and will depend upon the explosive used,

the characteristics of the rock, the number of holes, and

the kind and depth of the round drilled.

‘..

 

as an eranple, the following distribution was
foand to be best in a lG-holo round 5; feet deep, containing
three pairs of V-cut holes drilled in a 5 x 8 foot drift in

limestone at the Copper Queen mine at Disbee, arizona:

 

Cartridges
2 center 7 cuts - 7 each
4 side V cuts - 6 each
Center breast - 5 each
2 side breasts - 4 each
Center hinmer - 5 each
2 side shimmers - 4 each
Back - 3 each
3 lifters - 4 each

For ordinary work, it was not considered practic-
able to use parts of cartridges. When the cut holes broke
as expected, one less cartridge per hole would have been re-
quired for the other holes of the round. However, occasion-
ally the cut holes failed to break well; and in each case,
the extra cartridge partly made up for this deficiency, and
a fair break for the round was still obtained. Lifters are
almost always overloaded. A missed hole at the bottom of
the round is more dangerous than one elsewhere, as it is
likely to be covered with the broken material from the other
holes. Should it not be noticed, it might be picked into
by the shoveler. One reason for overloading the lifters is
to make a misfire more evident. An excess of ex losivo is
also used in the lifters to throw back the broken rock on
the shoveling sheet to make the work of the shovelor easier.
Where it is necessary to shovel back rock to set up a column
excessive exnlosive is also used to throw as much of the rock

back fram the face as possible.

iiisfires

Safety of Operation is the first requirement in
loading holes, as it is with all branches of mining. The
charging must be done in such a.manner that no premature ex-
plosions occur. hisfires or cut-off holes are also a source
of danger that can largely be prevented by cars in loading
and by the use of preper explosives and blasting supplies.
misfires materially reduce the ”break” of the blast, besides
interfering with the work of the following shift while missed
holes are being reshot.

Despite precautions, the fact remains that occa-
sionally for one reason or another, a misfire is encountered
and it is important to know how to handle it safely. All
faces should be carefully inspected for misfires before any
work is done at the place. In case of a misfire in a drift
round, no one should be allowed to return to the face for
one hour if fuse was used or one-half hour if the round was
blasted electrically. hissed charges should never be with-
drawn from a hole but always reblasted by inserting a fresh
primer in the top of the explosive. Re picking or drilling
should be done in a face in which a misfire occurs until the
missed charge is blasted. Where no stemming is used, it is
a simple matter to push a new primer down a hole and shoot
it in the ordinary manner. When stemming is used, the charge
may not fire through the inert material, in which case the
stemming must be removed. Where the stemming is in paper
shells, it is generally removed with the iron scraper used

for cleaning holes. There is an element of danger in this,

and washi.g the stemming out with water from the blowpipe
would appear safer.
Shafts, Hinges and;§aising Rounds

The procedure used in blasting sinking and raising
rounds is essentially the same as that in blasting drift
rounds, with the exception that electric detonators are used
instead of fuse and detonators.

All shaft rounds should be fired electrically so
that the entire crew can be out of the shaft before the
switch is thrown. Great care must be exercised to see that
the delays are properly loaded so that all holes will fire
in the desired order.

ihile small shafts requiring thirty holes or less
per round can usually be fired with a blasting machine using
a straight series connection. it is generally more satis-
factory to use a power circuit and connect the caps in either
straight parallel or parallel series. Connections in shaft
work are likely to get wet and if series connections are used,
some holes may be shorted out, causing a poorly pulled round,
loss of time, and possibly a serious accident. This trouble
can be largely eliminated by using the straight parallel con-
nection and firing with the power circuit. When the work
is not too wet, the parallel series hook-up may be used, con-
necting all instantaneous caps in one series. all first de-
lays in another, all second delays in a third, and so on,

finally connecting all these series in parallel.

TEST DATA F’CI‘! 51722.11] 01’" 252132-33 BULLETIN #511
Relationship of Planes of Weakness to the Quantity
of Explosive hoggirod for Breakingyhrift Wounds
To obtain data on the relationship of the planes
of weakness to the quantity of explosive required for break-
ing drift rounds. the blasting of a series of eight rounds
was observed at the Pilares nine of the hoctezuma Copper Com-
pany in April, 1927. These rounds were all blasted in a
hard-drilling, difficult-breaking porphyry. ?igure 21 shows
a standard lS-hole round used at the Pilares Mine. Rounds
were blasted with.60 per cent gelatin dynamite. Stemming

was generally used in the rounds.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Standard lS-Hole Round, Pilares hine

A description of the rounds and the results of
blasting are shown in Table 2, and Figure 22 is a curve
showing the relation between the quantity of explosive re-
quired per foot of advance and the classification according
to the planes of weakness of the rock. The points used are

for the estimated quantity of 40 per cent gelatin to give

an eqzivalent of the prepulsive energy of the 63 per cent

strength used. Th

e same classification scale and symbols

for the planes of weakness were used as those shown in

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 10
Size Ho. Depth Drilling a . Explosive Est.§quiv.

Round of of of Speed Sym- per ft. 40%
No. Reading Holes Round in.[min. bol Advancgz=~gelatin
es 5 x 7.5 16 3.5! 9 6.5 8.65? 9.9.?
70 5 x.7.5 13 4 9 7 8.0 9.2
71 5 x 7 10 5 6 9 5.0 5.8
72 5 x 7 16 3.5 10 7 8.6 9.9
73 5 x 7 13 4 -~ 7.5 8.0 9.2
74 5 x.7 16 4 6.5 6 9.2 10.6
25 5 5 Z 16 J 7 9 7,5 Q.6

Table 2

thefers to the classification of the planes of weakness in
the rock as described in Table l.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

'fi
Em
E \\
394" \
I. 7:
‘0 8 “\:\\~23
‘56 g.\
Q. 74
§5
34
°§a
a;
.5 6 7 8 9 lb II

EXPLOS/VES (40% GEL.) PER FZ' crepe/v CE

Curve Showing Relation of Amount of fixplosive
and Planes of Weakness

uC-fi-

Typical Drilling and Blasting Procedure as Used in
the Portland hine,AVictor, Colorado

It is impossible to give a complete picture of the
specific methods of drilling and blasting used in present-
day metal mining as the procedure will vary considerably
with the individual mines, types of rock encountered in the
various localities and.with the ability and knowledge of
the men carrying out the work. The procedure used at the
Portland Mine may be considered as representative of a metal
mine and is herein given to illustrate the use of some of
the general principles of drilling and blasting that have
been stated previously in this paper.

The standard size for drifts and cross-cuts in
the Portland Mine at Victor, Colorado, is 5 x 7 feet. Three
lengths of steel are used for drilling most of the drift
rounds. The starters average about 2% feet long: the second
steels are about 4 feet long: and the third is from 5% to
6% feet in length. The gage of the starters is 2 6/16 in-
ches, and there is a difference of about one-fourth inch in
gage in each successive bit. The average drilling speed is
about 9 inches per minute.

Rounds are drilled and blasted on each shift. Cross-
bars are used for holding the drilling machines. One set-up
is made near the top of the drift, and all of the round ex-
cept the lifters is drilled from this position. By the time
these holes are drilled the shovelers have removed the bro-
ken rock, the bar is set up near the bottom of the face, and

the lifters are drilled. The first position of the bar is

usually a pick handle length (51 inches) from the top and
the same distance from the face of the drift. Some miners
place the bar a little closer to the face to give the cut
holes greater pitch. figure 23 shows an average ld-hole

round in hard rock at this mine.

 

 

 

 

 

 

Typical 18-hole Round, Portland Mine

Thirty-five per cent strength special gelatin dy-
namite in 1 1/8 x 8 inch cartridges is used for all blasting
in the mine. The holes are loaded to near the collars, and
no stemming is used. He. 6 primers and fuse are used for
blasting drift rounds. ?rimers are made accord?ng to the
miner's preference. host mdners in the district insert the
capped end of the fuse centrally in the end of the cartridge.
In loading primers the fuse is not turned back along the cart-
ridge except where two primers are used in the same hole. in
which case one is turned and for end in order that both lengths
of fuse will extend the same istance from the hole. The cap-

ped ends of the fuse are protected from moisture by dipping

A“

.9 .... 1. fl .,.,
10.1.0119 .LOJ.

rounds, at the

cessive number of his

Eouble

#711-

then into an a.ir-dry-u3

tile 1111;130:360

insulator liquid,

.Ji tl‘”d, set

are

fires do not 0:

A large proportion

which appears to

of the

but apparentl" an ex-
"|. . ‘. .9 _
our iron this caise.

primers are used in nearly all lifters.

Data for twezlty—ninc and t.7onty-one rounds, res-

pectively, in two headings at the

Portland fiine, furnished

by Prod Jones, General Superintendent of the mine, are as

 

 

 

 

 

follows:
he, 1 30, g
Place - 2,500 crosscut. 2,400 N. 3 drift S.
Ground - Eedium.soft. Fairly hard, "revel-
1y" 0
No. of holes - 15 13
Powder used - 93 cartridges 1 1/6 80 cartrid 383 l l/B
x 8" 35. gelatin x 8” 35$ gelatin
dynamite. dynamite.

Types of round -

Distribution of
powder —

Advance, ft. per
round -

Powder per ft. of
advance -

Fuse per round -
Cost of powder per
linear ft. advanced

Cost of cap per
linear ft. advancew
Cost of labor per
linear ft. advance-

Total cost -

 

3 back, 3 breast, 3
cute, 3 liftersgcen-
ter cut a center
lifter connected at
bottom a detonated
t 0136 tlle 1".

7 cartridges in lif-
ters; 6 in all other
hOIOBQ

3.2

14.9#, average for
29 rounds.

129.5

$2.023

$0.223

X4.190
6.436

‘5

f

 

2 back, 6 breast, 3
cuts, 2 lifters.

7 cartridges in cuts
& lifters; 6 in out-
side breast; 5 in
center breast and
back holes.

3.7.

10.253, average for
21 rounds.

158.6

$1.375

$0.234

$4.823
$6.452

 

 

7“” Y' ‘ Q“...'
L: 'V '8--;«o '0'. h b‘

Development oyerations consist of drifting, cross-
cutting, sinking and raising. In each of these, drilling
and blas in; is an important part of the work ani the general
procedure used is similar in all four phases.

Gelatin dynamites, rau;i.5 from 33 to 83 per cent
strength, are the most commonly used explosives in metal
mines. This class of dynamite is adaptable to most of the
conditions not in dOVeIOpmcnt work, alth ugh special gelatin
dynamites are used occasionally in some mines. Ammonia dy-
namite may be used in some work where a bulky charge of lesser
density is an advantage or the saving in money justifies its
use.

A cartridge size of 1 1/8 x 8 inches is the stan-
dard used at most mines. In any case, the size should be
as large as can be easily loaded into the bore hole so that
a high density may be obtained and minimum amount of "free
space" left in the bore hole.

The cut holes of a round are the most inpertant
and care should be exercised so that these holes are drilled
and loaded as to give the maximum break. The depth to which
the other holes will break is largely dependent upon the ef-
fectiveness of the cut holes, and when the cut holes break
well, a full advance for the whole round is generally assured.

"7'"

The 7 cut, or "

Pyramid" cut, is the type which is most com- ‘
monly used and will produce a larger crater than the "Burn"

cut or "Toe" cut. The depth and volume of this crater can

be increased by usinQ h1Qher strength dynamite than would
be necessary the surrounding holes. Also, tests Lave
chose the t so per cent of the explosive for a roimd should
be concentrated in th a cut zolcs.

the planes of w~e skgk 33 is the rock bear a direct
relationship to the amount of explosive necessary to break
a given round. Therefore, it is 1t1psrtant that these planes
be taken into account in placing the drill holes so that a
saving in explosives may be had.

It has been shown that the standard round for a
inen class of rock under given conditions will reduce the
cost per foot of advance. The placing of holes in a stan-
dard round can be best accomplished by observing the break
which occurs by firing a round one hole at a time. flounds
should be desiand to tel 10 advantage of re gslar planes of
weakness which occur in the rock.

Primers should be made so that they satisfy the
following condi ions:

1. That the igniter or dotonstor cannot be pulled

out of the primer cartridge.

2. That the detouetor be in the safest and most
effective position in the primer cartridge.

3. That the fuse or wires of electrical firing
devices are not subject to harmful strains.

4. T1 ist the arimer is waterproof if necessary.

5. That the whole primer assembly can be loaded
safely, easily and in t:r 13 prefer; ed position
in the charge.

The charge should be tsmped in the bore hole as a

higher density will give more energy per cartridge.

Stemming increases the effectiveness of the charge

and should be used unless there is a valid objection to its

uBOo

minimum of u sfircs will occur.

1.513

11.31,: 15’ ¥=

"\
‘I

5v

0.

Care should be ta:

place in any cps:

)nl'
“V

L

1 or.

u in all Operations so
hurried or careless

-1 .. .1. -QQ -.- 5.1..1 .
.uic 1a.olves one use

II.

III

IV.

V.

VI.

cougar; A '7‘, fit

:t? m v'fi T‘.'.-"".~T1""*.T
a-.. -‘I .J.1-‘4
:fi T -.~:‘:'“."
..Ifio‘J séc.1.

80H???”
...Lu.,4.-.:l '
131””2.‘ (".73 ‘1

A c-1'LK’A.J do

fi Q I - ‘-

Tvrrn'fi O?— 'vnrfi“: 3??
Al. --.'1- '~‘-‘-.¢~I~‘.

'hfr- hv'vfi,
& 3).. M).

A.
B.
C.

VICE: O"?

THJ’LY

1'4.

P.
Go

I.‘

v "arr-"7'": “0 r1 nf‘fifim‘?‘ ‘6‘ '-"
a”. D r- u"_...-..'-_I')..‘:l O" 0;, _4;'-...;.-.3.Io-

IN “

I ...... —’A. "In-L J .....I
r\‘¢

1.)," ~Tr
JIJV'LI LO; semi-i

:1" ”A G3 0

Drifting
Cross-cutting
Raising
Sinking

I! [Tqrvjn

«gs/v) u-vmnr 3.
”‘0‘

5 Job or...“ 0-6...

0:“ - ~v1-_-. r

o lde .1)

0 IVT

Various 5rades and composition.

Gases developed.

Strength or pressures developed.

Size of cartrid5es.

Facts concl'ded for prep )er selection.
-..?I‘l“, O? CUTS

”V" out with sketches.

”Draw" c1t or "Toe" cut with.sketchcs.

“Fyremid"u cut with sicetches.

”fiich15dan or ”Burn" out with sketches.
" T33 PESEG" OF RDUHCG AKD THHIR “V'LOAH

Crater theory and effect of physical

characteristics of rock.

Effect of planes of weakness.

Classification of planes or weakness.

Theory of designing rounds.

DevelOpment of drift rounds.

1. Depth of rounds.
2. Stenaard rounds.
raising rounds.
Sinking rounds.

r v- 1-" c I" T‘
EIZIthiax 3 a. ' 7 31V

\l;c—QJ' '-

Slnker drills
Drifter drills
Steper drills
Drill carriages

.Tr‘vr [of T" Yf’jf'"

“J

«VT.

4“.

'3

D

VII.

VIII.

IX.

- th’iTfi‘Vfl r
Lil-WAJuuooJ L1

A.

T33? DAmA

(..-... v-nc-CQ

Uv.i.' $34131.

‘ko'I m hr-vrs'f‘fl
at A

klv U~.J~- Q.)

Primers
1. Cupping faze.
2. Stren3th of detonators.
5. Iandli n3. dotar ate?

4. Eotzois of makin3 Srlmors u:.th
fuze and detonator.
5. "akin3 primer 3 with eloctric
delay detonators.
fiosition of primers in bore holes.
Tamping.
Stomglng.
Firing holes with fuze and dotonator.
Lot holes.
2. Waterproofing fuzo.
firing holes with electric delay detonators.
Amount of explosive per hole.
malin3 miaflroa.
:lasting snafts, winze ana raising rounds.

mj’: 32:2:‘Mnjij OF 2.: .1-..) BULL 3le {7311

Relationship of planes of weakneas to the
quantity of explosives required for breaking
drift rOAnda.

Typical drilliA3 anu blasting proce are used
in the Iortland Aine. Victor, Colorado.

-68-

fi‘ ‘? f... .U "m
AUI“ IL’IiLl‘JLC in H}.

I am indebted to the followinr persens and firms
for furn1sh1’ n3 no Jlth help and.mater1aI, which were of
value to mo in compiling this thesis:

Professor Alundsen, Agricultural Extension Eopartment, Elohi-
5an State College, Last Lansing, Alch1;_;an.

W. L. Sever, Sales fiepresontatlve, 3.1. cu Pent do KOAours &
Company, Bay City, Eichlgan.

John Jeffries, Assistant to Llrector of tales, Atlas Powder
Company, nilmlng ;ton, Lelaware.

Francls Thomas, Clvil Ln31neer, Ishperzin53,2fleh15an.
E.J. Longyear Company, Klnnoapolis, Kinnesota.

The Axplosives Lnrineer, ullnziz.5ton, Lelarare.
Hercules Powder Company, hilmin 3ton, Delaware.
neGraw-nill Catalog Service, new York, new York.

The Cleveland hock brill Company, Cleveland, Ohio.
Ingersoll-Rand Company, Phillipseurg, Lew uez~sey.

Le Eel Company, Eilwaukee, Klscensin.

'LIC&30 Pneumatic Tool Company, How'fork, Kew‘York.
Gardner-Lenver Comp any, guiney, illineis.

3.1. du Pont de Honours a Company, Wilmington, Delaware.

American Institute of K1n1n5 u 2.0tallur51cal An3ineers,
Now'Ye erk, new York.

chhlgan State Department of Conservation, Lansing, Kichic
van
t, O

Coolegy Department, ulcnlgan State Colle' 56, Last LaAelng,
1.11.0111 gun.

BIBA I O GRAPE.

Friller's handboqg, TA Clevelanu neck rrlll Comrany.

 

Bock Excavation - Cathode & Cost, Lalbert Powers Slllette.
Elastor's_§endbook, L.I. Cu Pont de fiemours LC Company.
.tggg3taeto 1n 3 asting, A.e. :rcenfelder.'
:unr.olf -ng, Gnarles Prolini.

Blaet1n3_with L13L pg“losivcs, W.G. Boulton.

Yr1111n35fi Planting 1n Vctal Vino “r1fts & Croescuts,

5.x. Cara Aler, (Awn eau of Iinee Billetln 3 .

 

 

“rillin' ~ “last’ n3 in fore American Votal Hines, Theo~
Core Larvln.

! - '5‘
M33“

 

*—

 

Ln...
0
a
on.
..n
e
(x

. , 1
i-UCi

a
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51
“£30

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inle; llfi~~

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71-“? f)
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iya

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a
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back

=Ckea

LC

ligan

Jfic?

~4

 

7'1
J,“ 013.9
ELJ ‘f 1i”). ’
’Jeneral
Emfihov
-‘l‘".:§ .
.JJUneagm

gentlemen:

\ \‘

on p1 antinv 0 use tho\sfihfieo+
and Blast
W o flpgfee 1n /
.5 wOulJ grefiTij\,pprew
oiate it if you rquJ Send me any bfilietim
of informo+f ion vou méj have concerning the
”fichioerfi and d?+1i1nd OPBIHTlOfla in Metal
mines. I am abovebte in the tV“9s and costs
of the drill nqoh he ery UQQQ and your zeoommolm

Jation. as to thelfi/usa anger-va”ious cond’ tiOflSa

6

rjn

Inasoucn as/ fihe +hesis mu at be in
caéé L would aprQCioEe 1t if you
would San anv i3lu«s tzations of vour equip—
ment iv m ipllcate, Ifzthere is on y charge
for Elis\i"o ormation, I will be glao to re»
imburse you\x.

\‘.__n_/
\ \‘_« _
Thanking you in advance for any

help you may give to me, I am

a
,

Sincerely,

PeJ. Rockenbach

Adaress:

L
‘P.sJ. Rockenbach
767 W. Ionia

Lansing, Mich.

i"

‘3

u
(

 

DIAMOND DRILLING
SHAFT SINKING

GEOLOGICAL AND
MINING REPORTS
MANUFACTURE OF

DIAMOND DRILL?)
AND SUPPLIES

n Vt t ‘w V‘x‘; A x . if K1 , ‘ "\- " r .‘ '\ 7 V
mm (A “MA ( A >\IIA\\ a
lVIIPfilflSIC} ICINICBIIVTEIIE:F{ES

GENERAL. OFFICE
FOQHAY Toer

IVIINNEAFDOLIS 2,MINNESOTA

June‘% 1947

Mr. P. J. Rockenbach
707 W. Ionia
Lansing, Michigan

Dear Mr. Rockenbach:

Thank you very much for your letter of June lst in
which we cannot help but be interested.

we are glad to send you our complete catalog and
recently published Bibliography of Diamond Drilling under sep-
arate cover, both of which may be of interest. we believe that
after looking over the catalog you will find certain equipment

which is of major interest to you, and if you will advise us of
those models in which you are particularly interested we will be
glad to send you additional copies of the bulletins and can pos-
sibly locate some reasonably good photographs Which you might
wish to use..

If it is at all possible for you to do so, we suggest
that you might like to take a trip up here and discuss those
points which would be of interest to your thesis. If this seems
desirable to you, it would be well to let us know a week or ten
days in advance so that we could plan to have some time to discuss
your work and be sure that the men with whom you wish to talk will
be in the office.

Yours very truly,

E. J. LONGTEAR COMPANY
R. L. Loofbourow
Sales flanager

 

 

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1-1!» v\«

 

 

 

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I
I

It] Will III“ [III

1293 03168 80

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