McGr a w- Hi l l
Pu b l i s h i n g Co m p a n y, In c J a m e s H . M c G r a w , P r e s i d e n t E . J . M e h r e n , V ic e - P r e s id e n t
C g a LA g
D e v o te d to t h e O p e r a tin g , T ech n ica l an d B u s in e s s P r o b le m s o f t h e C oal-M in in g I n d u s tr y
R . Da w s o n Halt* E n g in e e r in g E d ito r
N o P lace fo r P o litics
A
D D R E S S IN G the leg isla tu re of W est V ir g in ia on l May 3, the opening day of the extraordinary session, Governor H ow ard M. Gore criticised th at body fo i its fa ilu re to confirm the appointm ent o f Robert M.
Lam bie to succeed h im self as ch ief of the D epartm ent of M ines. Those who have follow ed the course o f vv est V ir g in ia politics during the past tw o years are conscious o f a lack o f harm ony betw een the governor and the leg isla tu re or an influential group w ith in th at body.
W ith th is situ a tio n Coal A g e is not concerned; it is con
cerned, however, w ith the character of man chosen to head the departm ent of m ines and w ith his fitness fo i th a t office.
F ew executive officers are charged w ith g rea tei re
sp on sib ility. The w ork calls fo r a high degree of technical skill, for courage, personality, resourcefulness, constructive execu tive ab ility and an understanding o com plex hum an relationships. The rapid grow th in the production o f coal in W est V irg in ia throw s an ever in
creasin g burden on the head o f the department of m ines and on h is subordinates. The leader is charged w it th e protection o f thousands o f lives and of property w orth m illions o f dollars. S a fe ty work m ust be planned and encouraged; in some cases it m ust be enforced.
F ir s t aid and m ine rescue m u st be made part o l the common practice of every u n it of th e industry. ^ Mine inspection m u st be thorough, in telligen t and fa ir . A1 th is con stitu tes a job fo r a real man.
Coal A g e is not here u rg in g th a t the reappointm ent o f Mr. Lam bie be confirmed. I t is th e duty of the gov
ernor to appoint and o f the sta te legislatu re to
or to reject. T h is periodical m aintains, however, th at n eith er Mr. Lam bie nor any other state m in in g ch ief should be appointed or rejected because o f h is political relationship either to th e governor or to the legislatu re o f h is sta te. The final selection should be based solely on m erit— on th e fitness o f the man for h is official re
sp on sib ilities. I f there be reasons other than po 1 ics fo r w ithholding confirm ation in the case o f Mr. Lambie th ese should be m ade public.
A M onth’s Shutdow n
A
T MOST i f not all anthracite collieries, inasmuch . as the product is sold largely, if not wholly, as a dom estic fu el, th e hot m onths of the sum m er are dul tim es. T h is is particularly true o f the m onth of A ugust, fo r then not only .is the w eather hot, so th a t little or no coal is needed, but th is is the m onth w hen m ost people go on th eir vacations. Much of the m ine outpu during th is season o f the year m ust a c c o id in g y go ostorage. , _
It has been su ggested , therefore, that at least some o f the hard coal m ines m ig h t advantageously shut down during th is m onth. Such a shutdown would accomplish several th in g s. It would not only stop th e output at a tim e w hen it is lea st needed, but it would afford an
excellent opportunity to pu t'h oists, breakers, w asheries, and other equipment in proper condition for continuous operation throughout the balance of the year. It would afford a tim e for all em ployees in the operating depart
ment to have a good rest and be in good shape fo r the other eleven strenuous m onths of high-pressure p io -
duction. ,
Both men and m achinery give best resu lts when working at or n e a r th eir capacities. In like m anner, both need rejuvenating periodically. W hile th e m a
chinery is being repaired by the m echanical departm ent, the monthly operating men could be put on h a lf pay and afforded an opportunity to go fishing or otherw ise recuperate. So th at when the tim e comes to start operations in the early days o f Septem ber, all the operating force and all of th e equipm ent should be in excellent fettle. ___________
Practical Training
T
HE D E C ISIO N o f Carnegie In stitu te o f Technology to abandon its special tw o-year course in coal m ining because of lack of support represents a chal
lenge to coal operators everyw here but m ore especially to those in W estern P ennsylvania. The course^ w as designed to m eet the needs o f practical coal m ining men, m any of whom had not gone beyond th e grade school. T heir practical experience, however, acted as a splendid foundation on w hich to build a degree of engineering tra in in g th at would make them b etter fore
men and better superintendents.
The students tak in g th is course have financed them-:
selves. In the case of m arried m en th is has frequently meant th at entire fa m ilies have made sacrifices for years Many o f the men have loaded coal on Saturdays and holidays to earn tu itio n and board w hile in school.
It is true th at m any students work th eir way through college but it requires a h ig h degree of in itia tiv e and courage for men who have worked in the m ines to give up earning and devote tw o years to study w ith its attendant expense.
The course itse lf “g ets down to brass tacks. The men already have the flavor o f the industry. N eith er students nor instructors w aste tim e. They know w hat the course ought to prepare them for. T heir back
ground o f m in in g problems enables them to know how and where to apply th eir new ly acquired engineering knowledge. There is a real need for th ese men as rapidly as they can be graduated.
Unfortunately conditions in the coal industry during the past few years have made it quite as difficult for prospective students to lay by the necessary tuition fees as for the operator to build up a surplus. Carnegie Institute, facing many demands upon its funds and its teaching energy quite appropriately becomes discour
aged when only six or eight men register for this two- year course in coal m ining. ^ ^ ,, , ,,
It rem ains for operators to dem onstate th a t they are interested in th is course and in th e m en so trained.
T hey can do th is by co-operating- w ith the com m ittee appointed recently by W. L. Affelder, chairm an of the advisory board, con sistin g o f M. C. Angloch, o f V esta Coal Co.; W. H. Glasgow, H. C. F rick Coke Co., and W. E. Fohl, m ining engineer. Co-operation o f oper
ators in P ennsylvania, particularly, w ith th is com m it
tee w ill not only reopen th is course but m ay even arouse th eir in terest to th e point where w orthy m en m ay be financially a ssisted to take it. The raw m aterial is th ere; th e tra in in g is available. Coal A g e believes th e coal in d u stry w ill be well advised to make the m odest in vestm en t necessary to w in fo r it s e lf 1 the finished prod
uct— practical m ining men plus tw o years o f specialized train in g in the fundam entals o f m ining m anagem ent.
718
V alue o f . G oodw ill
N
OT SO -LO N G AGO a com pany sold its goodwill fo r $50,000,000. It w as enabled to obtain th is sum ow in g to its p ersisten t publicity and its m arketing of a readily salable product w ith copyrighted nam e. T his fa c t is fer tile in su ggestion . W hat is the goodw ill o f the average coal com pany? Some producers are not even seek in g to lay the ground fo r any such profit. When th e m arket im proves th eir prices go up unreasonably and the quality o f th eir product deteriorates. Goodwill for individual firms cannot thus be built up, nor can th e industry as a w hole a tta in such an a sset by these m ethods. Some com panies are tr y in g to protect th eir goodwill by stead y price and h ig h quality. Others by m ixin g disks w ith th e ir product or issu in g stam ps (one fo r each ton sold to be attached to delivery slips by reta ilers) are endeavoring to prevent in ferior coal from b ein g delivered in place o f th eir own and as i f supplied by them .
And goodwill between em ployer and employee is w orth real m oney. It is generally stated th at industry in Great B rita in has been ruined by a lack o f goodwill, th e coal industry in particular, and coal operators in th is country have not sou gh t th is in tangible a sse t as co n sisten tly , as th ey m ig h t have done. O verlooking goodw ill is a sh ort-sigh ted policy. E ith er a halter or a garland w ill be hung over th e shoulders of the fu tu re;
which it w ill be w ill depend on the character o f the past. A ny com pany th a t desires a fu tu re fre e o f bicker
in g and financial d isaster m ust plan all its operations so as to guarantee its future. T hat does not m ean solely that it shall comply w ith th e letter o f law alone or w ith th e dictates o f ju stice, but rather th a t it shall show such fo resig h t, g en erosity and patience as is calculated to w in the loyalty o f its men.
A Tragedy o f W aste
W
H E N T H E M IAM I C O N F E R E N C E betw een the Central C om petitive F ield producers and the U nited M ine W orkers broke up, unofficial forecasters o f labor stra teg y said th at the union would next propose d istrict agreem ents and, fa ilin g in that, would seek to n egotiate contracts w ith individual operators. Recent developm ents have attested to the soundness o f those p redictions. Indeed, th ere is concrete evidence th a t the union is ready to make individual agreem ents before the question o f d istrict settlem en ts has been disposed of. A t lea st one such contract already has been made•and there are unconfirmed rum ors th a t other individual tw o-year agreem ents are pending.
The present plan is to bind the individual operator to a renewal o f the term s of the Jacksonville compact w ith the protective proviso th a t any change w hich may be incorporated in a more general contract w ill auto
m atically become part of the individual agreem ents.
Superficially such an arrangem ent seem s m ore than fa ir to the individual operator since it assu res him the benefit o f any m odifications w hich m ay be made later in col
lective b a rgain in g w ith other producers sim ilarly situ ated. A ctually, however, th e exten sion o f th is process o f sig n in g individual agreem ents will destroy all chance o f a constructive . readjustm ent in labor relations in the Central C om petitive Field.
E very individual contract naturally encourages union officials to push th eir cam paign fo r such settlem ents.
E very individual contract m akes it ea sier fo r some other operator to sig n an independent agreem ent.
O bviously if the m ovem ent g a in s headw ay, the tim e will come w hen the U nited M ine W orkers w ill have suffi
cien t tonnage sign ed up to sa y to the rest o f the opera
to rs: “H ere is the contract; take it or leave it.” AH hope o f m odifications vanishes. T hat part o f the in dustry which cannot or w ill not turn to open-shop operation as the only w ay out again is saddled w ith the Jacksonville compact fo r another tw o years.
N eith er the union operator nor the union m ine worker would benefit from such an end to the present labor controversy. It would lead inevitably to a fu r
th er contraction of the sphere o f union influence and to still fu rth er decreases in the annual earnings of the union m iners. It would lead, too, to a fu rth er unbal
ancing o f production and d istrib u tion w hich in th e long run w ould be harm ful to th e industry as a whole. Such a trium ph of opportunism would be a traged y of w aste in which nobody would suffer m ore than th e operators and m in ers who had made it possible.
Vol.31, NO.20
Face Forem ost
O
P E R A T IN G FO R C E S a t coal m ines h a v e been long educated to the old tim e-honored system o f p ayin g by tonnage. They have learned to pay m ore regard to th e work o f th e m en engaged in the sm aller jobs around the m ine. T hey have by long experience become accustom ed to su bordinating m in in g to transportation.
Though the law demanded the presence o f th e forem an w here the m iner w as w orking, specified the frequency o f h is v isits and did not require him to be at any tim e on th e haulw ay or tipple, neverth eless it w as only the odd m om ents th a t he put at th e face.
N ow th a t w ill all be changed. In terest as well as the law w ill make him v is it th e fa ces in person or by proxy.
H ow ever, he w ill be slow to recognize th a t h is in terest has changed. A fter, years o f practice in one course o f action it is difficult to recognize en tirely new conditions requiring a new course o f action and it m ay be n ecessary som etim es to le t the forem an follow h is bent. Men can be appointed to keep the face men in active operation and the forem an can be allowed to continue to supervise the m ine in h is own w ay and as in th e days past. There w ill be need fo r expert men all along the line, th e tipple boss, the haulage boss, the road boss and the face boss.
So much has to be kept under observation in a mine, so m any chances o f m ishaps and bad m ining prac
tice, so m any m iles of roadway, so m any acres o f w ork
in g th a t i t is w ell sa id th a t m in in g needs more super
vision than any other operation and receives less.
G O A L A G E
■Pennsylvania Power &■ Light Co, (4,000 volts
No. 2 Lykens slope
Engine house I
\
\ m \^íñ^KEP(abandoned) I ? \ Office. (jjubji naTALI e«'School No. I Lykens
fan
, Substation No. 3 Lykens slope
\ *,No. 2 White
jk Slope
B o ile r house- Substation- Tun nel to N a ta lie No. 2 vein , Sth lev,
\ Drainage Tunnel Wash house
j Stable N Culm banks
P.R.R. *****
fro m H e a t p L a n N ^ . L ancaster Maga t i p e ^
sw itc h •
iL~——'S/ ~^~NfN
■ .it / } COLONIAL
BREAKER
■Substatk I Shaft '-Supply isnarr house COLONIAL C )LUERV
+.II,400 Volts Tunnel from Greenough
No. 4 bed s h a ft level
/Vp Carme! k. Rl£SL.
(P.&R. R-l
l No.BSlope
No.S bed No.bslope No. S bed
^¿Substation ,<-Boiler house
'*¿±30
P_Greenouah^a Shaft--’* »"
Shop-'_Jf±
/creenouoh breaker (.abandoned)
R o c k T u n n e ls R edu ce H a u la g e Costs
A t C o lo n ia l P la n ts
I
N T H E A N T H R A C IT E REG IO N, as in the bitum inous, “B ig g er and B etter M ines” has been the slogan o f operation. T h is principle has often been exem plified w hen m ines w ere brought under a common m anagem ent by financial consolidations. In tim es past, th is has often m eant only th e b rin gin g o f coal fio m d rifts, slopes and even sh a fts, usually on the surface and w ith m uch increase in transportation distance and expense, to a large central breaker, increasing the ton
nage of th a t u n it and creatin g a d iversity factor th at afforded a m ore regular demand on the capacity of the m achinery o f preparation.
A t one plant, at least, it has had a more radical con
notation— th e creation o f en tirely new and underground avenues o f approach to th e new breaker, by which the cost of operation h as been greatly decreased. B y th is m eans the transportation cost has been lowered rather than raised, th e preparation charges have been reduced and the disadvantages o f outside haulage in the w inter have been elim inated. The holding of cars on the sur
fa c e w here th ey w ill be exposed to the rigors of the w in ter and w here the coal may be frozen also is avoided.
Colonial Colliery Co., an affiliation of M adeira, H ill &
Co., had tw o breakers, the N a ta lie and the Greenough,
Coal is tran sp o rted to new shaft and breaker through gangways in solid rock—T hus two breakers are replaced by one w ith o u t the need to construct costly surface roads having railroad and h ig h way crossings and either long detours up valleys or trouble
some inclined planes.
5,800 ft. or roughly a m ile apart, located in the Mt.
Carmel-Shamokin district. One, which w as built in 1900, had been operated by the Greenough Red A sh Coal Co., which later became affiliated w ith M adeira, Hill
& Co. The m achinery for preparation w as regarded as obsolete having long circular screens fo r sizin g the coal.
The sh aft, however, w as still in good condition and would have rendered efficient service fo r m any years.
The other w as the N a ta lie breaker, a fram e struc
ture, erected in 1911. A ll the coal treated in th is plant w as hoisted by m eans o f slopes and transported on the surface to the foot o f the structure. H ere a portion of it was dumped into a conveyor line, 54 in. w ide, and conveyed by it to th e top o f the breaker. The rest was hoisted in m ine cars to th e sam e elevation.
A s m ight be expected, th is system required much rolling stock. Som e idea o f the exten sive outside tra n s
portation problem o f the old N a ta lie breaker can be gathered from th e fa c t th at there w ere on the surface six steam locom otives and 195 m ine cars w hich traveled
M A Y 1 9 ,1 9 2 7 C O A L A G E
M g . 1— T h e T w o Old P la n ts and th e N e w O ne by W hich
T h ey W ere R ep laced
C o a l R u n C r e e k , o r H ic k o r y - S w a m p , l i e s e x a c t l y h a l f w a y b e t w e e n t h e t w o o l d c o l l i e r i e s a n d u n d e r i t i s a l a r g e s y n c l i n a l . I t s e e m e d d e s i r a b l e t o p u t t h e p l a n t o n s o l i d g r o u n d a n d t o s i n k t h e s h a f t t h r o u g h n o n e o f t h e w o r k a b l e c o a l s e a m s b u t r a t h e r i n t h e i n t e r v a l b e t w e e n th e m . S o t h e C o l o n i a l C o l l i e r y S h a f t i s n e v e r l i k e l y t o b e d r a w n o u t o f p l u m b b y c o a l e x t r a c t i o n . T h i s a c c o u n t s f o r t h e l o c a t i o n c h o s e n . H a d t h e s h a f t b e e n s u n k i n t h e h e a r t o f t h e H i c k o r y S w a m p , i t w o u l d h a v e b e e n w e t a n d w o u l d p r o b a b l y h a v e b e e n p u l l e d o u t o f li n e b y m i n i n g o n e i t h e r s id e . A B is a c r o s s - s e c t i o n l i n e , a n d o n i t F i g . 2 is b a s e d .
720 C O A L A G E VOL.31, NO.20
Cross-Section on Line A - B1 Looking West
500_ -too __I
F ig . 2 — Cross S ection o f
C o l o n i a l C o l l i e r y i s a t t h e e x t r e m i t y o f o n e o f t h e “ f i n g e r s ” o f t h e W e s t e r n m i d d l e a n t h r a c i t e fie ld . C o n s e q u e n t l y t h e m e a s u r e s lie r e l a t i v e l y h i g h ; t h e l o w e s t w o r k i n g is 8 3 2 f t . a b o v e t i d e a n d t h e s h a f t b o t t o m i s 1 ,0 7 0 f t . a b o v e t h e s a m e le v e l. T h e l o w e s t c o n v e n i e n t d r a i n a g e p o i n t w i t h i n t h e a r e a p e r m i t s o f d r a i n a g e a t t h e s h a t t b o t t o m t o a l e v e l o f 1 ,2 9 0 f t . a b o v e t i d e . I t i s e a s y t o r e a l i z e t h a t , b e c a u s e o f t h e
Coal M easures A lo n g L in e A B o f F ig. 1 b u t to a D ifferen t S cale
e n d n e a r t h e C o l o n i a l s h a f t . T h e m e a s u r e s h a v e in g e n e r a l a d o w n w a r d t r e n d t o w a r d t h e s o u t h , s o t h a t n e a r t h e N a t a l i e s lo p e i r r e g u l a r f o l d i n g , d r i l l i n g g i v e s b u t a n
i n d i f f e r e n t k n o w l e d g e o f t h e l i e o f t h e s e a m s , s o t h a t i t i s o n l y w h e n t h e m e a s u r e s a r e w e ll d e v e l o p e d b y o p e r a t i o n t h a t g o o d g r a d e s f o r h a u l a g e a n d d r a i n a g e c a n b e d e t e r m i n e d . B o r e h o l e s , h o w e v e r , d o g i v e s o m e v a l u a b l e i n f o r m a t i o n , a n d a l o n g t h e l i n e o f c r o s s s e c t i o n s t w o h o l e s h a v e b e e n s u n k , o n e a t t h e s o u t h e n d o f t h e l i n e n e a r t h e G r e e n o u g h s h a f t a n d o n e a t t h e n o r t h
q u i t e a f e w s e a m s a r e m i s s i n g t h a t t h e o ld G r e e n o u g h o p e r a t i o n d e v e l o p e d . N e a r N a t a l i e , h o w e v e r , s o m e o f t h e s e a m s in w h i c h G r e e n o u g h c o l l i e r y w a s w o r k e d m a y b e f o u n d t o t h e e a s t w a r d o f t h i s c r o s s - s e c t i o n lin e . A ll m e a s u r e s w o r k e d a r e m o r e o r l e s s b e n t a n d d i s t o r t e d .
G r e e n o u g h 3 i ' t o 4 '
to'1 SO' 2?
35'
5 l'( Ma rnrnoth 7 ) ’
over m iles of track of 36-in. gage. On account of th is exten sive outside trackage, delays w ere frequent and production w as greatly restricted, especially during the w in ter m onths w hen snow and ice accum ulated and the run-of-m ine coal froze in the cars.
T his breaker had equipm ent fo r preparation, excellent in its generation but susceptible o f im provem ent under more modern m ethods o f coal w ash in g. N ew breakers w ere needed, fo r the old ones w ere in bad condition and had heavy m aintenance charges. W ith consolida
tion, the question naturally arose w hether to build tw o new breakers or to erect a common
breaker th a t could ship over both roads, would combine both tonnages and would have a common sh a ft which would be connected under
ground by a system of tunnels that would elim inate m uch o f th e ex
pense of previous m ethods o f tra n s
portation.
The problem when fu lly stated answ ered its e lf and a new breaker w as erected w ith the n ecessary con
nections to both th e P en n sylvan ia and th e P hiladelphia & R eading railroads. W here the new breaker should be placed w as a m atter much debated and carefully considered.
F in ally it w as decided th a t it should be located on the north side o f w hat is known as the H ickory Swam p basin.
The location adopted required the sin k in g of a new sh a ft. Skip h o ist
ing w as seriou sly considered, but on account o f the fr ia b ility of the coal, it w as feared th a t th is w ould reduce the percentage of prepared sizes, so self-dum ping cages w ere finally adopted. The new breaker not only prepares its coal w ith less expense but m akes a better product than w as form erly shipped. Thus the Colonial Colliery Co. has resolutely discarded both th e old breakers fo r a new one
140
100
360
00'
N a t a l i e
"Ro.y
N o'S" ¡2
10— —
-3j-
F i g . 3 -
T h e b e d s a n d t h e i n t e r v a l s b e t w e e n t h e m v a r y s o m e w h a t f r o m p l a c e t o p l a c e . T h e s e c t i o n s a r e t h e r e f o r e o n l y a p p r o x i m a t i o n s .
located at a convenient point betw een the tw o.
The sh a ft w as located betw een the outcrops of th e lower and upper seam s as indicated in F ig . 2. It has tw o landing points, one about 80 ft. below th e top o f the collar and the other 300 ft. below th e sam e point.
The collar is 30 in. w ide on top and 40 ft. deep. The sh a ft has four h oistw ays to the 80-ft. level and tw o to the 300-ft. level. Each com partm ent is 6 ft . 1 0 i in.
w ide and 12 ft. 6 in. long in th e clear. The sh a ft also has a h a lf com partm ent 4 ft. w ide and 12 ft. 6 in. long.
T h is extends th e fu ll length o f the sh a ft and is used fo r column pipes; w ires, etc. The upper landing is a sim ple layout, be
cause it has to contend w ith only one type of car and one track gage. The layout o f the low er landing, how ever, w as much m ore difficult because it had tw o track gages, and three, different typ es o f cars had to be Handled on' it.
The Greenough cars are of the box type, of tw o capacities, 120 cu .ft. and 90 cu .ft. and have a track g a g e o f 44 in. The N a ta lie car has flared sides, a capacity o f 91 cu .ft. and a track g a g e o f 36 in. To w ork ' the bottom o f the sh a ft efficiently requires th a t cars of eith er g age can be. h oisted in eith er com partm ent. T h is re
quired a com plicated track layout. It w as finally solved as shown in F ig s.
5 and 6.
In order to connect the w orkings o f both operations w ith th e new sh a ft i t w as n ecessary to drive 12,000 lin .ft. o f rock tunnel. The tunnel to th e G reenough w orkings is 12 ft. w ide, 7 ft. h igh over the rails and 3,500 ft.
long. It has a ditch 2 ft. w ide and 2 ft. deep below th e bottom o f th e sills. T his tunnel w as started at t h e ' Greenough end and driven to th e dip.
I t w as finished about the sam e tim e as the sin k in g o f the sh a ft.
The tunnel to N a ta lie is 10 ft. widfc
No. 7
No.fci J4 0 .6 No. 5"
•-Buck---
M o u n tain No.4~
(No. 2 L y k e n s i --- i N o . b
80 4'
9'to
10'
b'
24'
4' 51'
350
50' 4 4 to
S '
•Two Cross Sections Of Seams
May 1 9 ,1927
Fig. 4— Cage L anding at th e N atural D rainage L evel o f th e C olonial Shaft
T h e t w o s o u t h e r n c o m p a r t m e n t s a n d ^ h e s m a l l r u n w a y r u n ^ « ^ W a t e r is p u m p e d J r o m t h e l o w e r l a n d i n g t o b y a t u n n e l to t h e s u r f a c e
Leve/
loads
F ig . 5— T rack s a t B ottom of C olonial S h a ft
t h e r e a r e o n l v t w o c a g e c o m p a r t m e n t s a n d o n e p i p e w a y T h e o f h e r t w o c o m p a r t m e n t s t e r m i n a t e a t t h e n a t u r a l d r a i n a g e le v e l 2 2 3 .1 2 f t . a b o v e .
and 7 ft . h ig h over the rails w ith a ditch 2 ft. w ide and 2 ft. deep below the bottom of the sills. T his tunnel w as 1,550 ft. long and w as driven from the N atalie w orkings. The ditch had to be made large in order to drain all w ater to a central pum ping plant at the foot of the new sh aft.
The drainage-level tunnel w as started from the sur
fa c e approxim ately 2,000 ft. w est of the new sh a ft. It w as driven on an ascending grade of 0.42 per cent to th e w orkings of th e No. 2 W hite Ash Slope, of N atalie, and w as approxim ately
5,700 ft. l o n g . T h i s t u n n e l ' i s 10 ft. w i d e and 7 ft. h i g h w i t h a 2 x 2 -ft. ditch. It w as started from both ends and rushed to com pletion.
A connection w as made w ith lihe new s h a ft a t the 80-Tt. level. T h is tunnel elim inated th e N o. 2 W hite A sh pum ps and drained an area which h as alw ays given much trouble a fter heavy rains.
W ith seam s havin g bad roof conditions and heavy grades, n ecessita tin g crooked roads and planes, it ^ is freq u en tly an extravagance to attem pt to conduct m ain- haulage operations w ith in the coal bed. A rock tunnel can be m ade str a ig h t and o f even grade and w ill g i eat y increase the speed of tran sit, decrease the number of m en employed, elim inate delays, decrease m aintenance charges and increase sa fety . T his principle, so effective in the reduction o f the cost of operation has not been em ployed as frequently as m igh t be desire . The conditions at the Colonial M ine w here a tunnel can be driven in the roek at favorable grades for 5,640 It.
w ith ou t leaving the coal-bearing m easures, a ie we su ited to th e establishm ent of such a haulage and drain
age system . ,
It w ill be noted th a t the lower tunnels are both arranged to have a down grade toward the Colonial sh a ft, m ainly, o f course, for drainage purposes. How
ever, th is aids haulage and reduces car resistance. The tunnel on the south running from the G reenough sh a ft has a fall o f 0.5 per cent, so th at the resistance to the em pties w ill be approxim ately equal to th at of the loads m aking an ideal condition. The tunnel on the n oith that leads tow ard th e old N a ta lie sh a ft has a g favor of th e loads o f 0.25 per cent.
A s already stated, by means of the rock tunnels the water throughout the w orkings is brought by gravity to the Colonial sh a ft and is forced from the 300-ft. to the 80-ft. level by four cen trifu gal pumps having a total capacity of 10,000 gal. per min. Two of these w ere transferred from the Greenough plant. A t the 80-ft.
level there are tw o pumps, one of 1,500- and one of 1,000-gal. per min. capacity.
It is clear th at the pumps in the lower level can deliver more w ater than the pumps in the upper level
can handle, but it m ust be remem bered th at the fu ll capacity, 10,000 gal. per m in., o f the low er pumps is utilized only in flood tim e. T his large quantity of w ater is never needed for the operation o f the breaker, so the excess w ater from th e two levels is allowed to travel w est to the surface through the drainage tunnel already described. E ventually the sh a ft w ill be deepened, and new tunnels w ill be constructed w hich will be ex
tended at least to the Hickory Swamp basin which lies ju st south of Colonial shaft. The Lykens No. 1 bed in the syncline reaches an approxim ate depth of 1,350 ft.
as measured from the collar of the Colonial sh a ft. T his problem, however, is a m atter fo r a rem ote future, for like m any anthi'acite properties th at at Colonial has a large number o f workable seam s, the approxim ate thick
ness of which are set forth in tw o cross sections, F ig . 3.
These thicknesses vary som ewhat from place to place.
Ly k e n s Co al Is Hard to Du m p
The Lykens No. 1 bed w hich is about 4 ft. thick at Greenough and from 44 to 54 f t. thick at N atalie, is a so ft bed producing a coal th at even w ith a car having a steel bottom does not dump readily. The Lykens No. 2 bed which is 34 ft. thick at Greenough and 4 ft. thick a t N atalie is a hard m easure g iv in g a large percentage of domestic sizes. T hese Lykens beds burn to a red ash.
They are m ined only at the N atalie end of the property where the coal m easures ta il out to the surface. A n
other of the im portant seam s, the Buck M ountain or No. 4, a w hite-ash coal, covers alm ost the entire acreage.
However, the N o. 4 rises to th e surface a little to the south o f N atalie sh a ft. A ll th e seam s above it, shown
7 2 2 C U A l l A G E Vol.31, N o .2 0
-> c nI
I 1
Fig. 6— Bottom of the Colonial Shaft
T h e r e is a n a p p r o a c h f r o m t h e G r e e n o u g h S h a f t a n d o n e f r o m t h e N a t a l i e w i t h r u n a r o u n d s in t w o d i r e c t i o n s . A s t h e r o a d s a r e a l l in r o c k t h e g r a d e s a r e n o t m a d e t o s u i t t h e i n c l i n a t i o n s o f t h e c o a l b u t a r e m a d e s o l e l y to a c c o r d w i t h m o s t e f f ic ie n t o p e r a t i o n . E a s y c u r v e s m a k e t h e c a r r e s i s t a n c e l i g h t a n d r e d u c e t h e l i k e l i h o o d o f d e r a i l m e n t s . T h e a b s e n c e o f w o r k i n g s m a k e s a s y m m e t r i c a l l a y o u t e a s y .
in F ig . B, appear near N atalie but not at the sh a ft itse lf, som e b ein g m ined by strip p in g m ethods.
In th e Lykens beds, because o f the presence of gas, th e m en are provided w ith electric cap lamps as a direct protection a g a in st explosions and w ith flame sa fe ty lam ps also so th at should any g a s be p resent th e men w ill be w arned o f its m enace. T his double protection a g a in st m ethane is quite usual in the anthracite region.
It is a fa ir ly norm al condition o f affairs to see all the m en a t a m ine carryin g both kinds o f lamps. Thus every em ployee is enabled to ascertain w ith ou t delay w h eth er he is w orking in a dangerous atm osphere.
Op e n La m p s Ar e Us e d
The beds above the Lykens are operated by open lam ps. The dangers o f m ixed lig h ts in a mine— open and closed— is alm ost entirely removed w here the two areas are separated by an interval o f strata from 350 to 360 ft. thick, only connected through sh a fts. It is an altogeth er different condition from th at w hich ex ists w here the m en are w orking w ith both kinds o f lig h ts in a sin g le bed o f coal.
It is tru e th at the lower drainage tunnel cuts the upper seam s near the Greenough sh a ft, w here the upper beds are worked, and also the Lykens beds near the N a ta lie sh a ft. T hus there is a connection on a grade alm ost level, but betw een the tw o is the Colonial sh a ft and th e distance is considerable. The trip could hardly be made w ith ou t th e m an m ak in g it b eing subjected to
inspection. The upper beds are also cut in the H ickory Swamp, but there the upper seam s are not b ein g worked and, when th ey are, there w ill still be the n ecessity of passin g the Colonial sh a ft in goin g from the upper
w orkings to those in the Lykens.
E ig h ty -six m ules and nine battery locom otives are used for gath erin g. Ten trolley locom otives are em
ployed fo r m ain haulage. Three undercutting m achines are used in th e flat coal near the Greenough sh aft.
Scoop loaders, electrically operated, gather the coal from the faces, sh ak in g chutes are also employed and a non- continuous belt loader.
T his patented loader w orks like a roller blind. It is spread fo r th ree m inutes during w hich tim e the men a t the face load it w ith coal. It is then rolled up, the men havin g a b reath in g spell betw een loading periods. It g iv es excellent results, the men filling the belt in
dustriously w hen the opportunity is afforded. A s in m any anthracite m ines having several beds all of which are being worked the air currents are separated, each being actuated by its own fan. There are th ree o f th ese fa n s at Greenough and an equal num ber a t N atalie.
There is, of course, a secu rity in th is m anner o f han
dling the ven tilation problem, less w ater g age is re
quired and leakage is accordingly less likely to occur.
The bottom layou t is shown in F ig s . 5 and 6. It w ill be noted th a t th e tracks are of tw o different gages, which adds com plication, but ca g in g is effected w ith ou t difficulty. The N a ta lie cars are o f 36-in. g a g e and those from G reenough of 44-in., n ecessita tin g double rails on th e cage and a sh ort w ay in the 300-ft. bottom .
The upper or drainage-level bottom is shown in F ig . 4.
H ere cars o f only one gage are assem bled. A ll the four and a h a lf com partm ents of the s h a ft can be seen in the line draw ing, fo r all come to th is level.
A s w ill be seen, the bottom and upper m ine landings are not in coal but in solid rock. The tw o little seam s between the Lykens beds and the Buck M ountain or No. 4, are o f n egligib le thickness and not worked. F or th is reason th ey are n ot included in the cross-section in F ig . 3. It w ill be noted th at in the low er level o f the sh a ft they are cut at a high angle, and in th e upper level are m ore nearly horizontal and not cu t a t all.
The P en n sylvan ia P ow er & L ig h t Co., a su bsidiary of the L ehigh P ow er S ecu rities Co. has th ree lin es into the plant, so th a t there is no trouble from pow er failu re.
Current is received at 66,000 volts. One bank o f tra n s
form ers w ith a capacity of 3,000 kva. has a secondary voltage o f 2,200 volts. T h is supplies Colonial Colliery w ith power. The other bank has a secondary of 11,000 volts and supplies power to the old N a ta lie and Greenough collieries. A t th ese latter operations are step-down tran sform ers th a t reduce th e voltage to 2,200 and 440 respectively.
The 2,200-volt circu it from the 3,000-kva. bank is led into a sw itch house from w hich four feed ers leave, each controlled by oil circuit breakers. T hey supply the follow in g groups o f m achinery: (1 ) H o ists, (2 ) inside pumps, (3 ) breaker, (4 ) com pressors and m otor- generator sets.
The h o ist to the 80-ft. level is driven by 300-hp. slip- rin g induction m otors. T h at to the 3 00-ft. level is of 900 hp. sim ilarly driven. The latter m achine is o f the cylindro-conical type. A rrangem ents are m ade so that when th e hoistm an is called to raise men, he cannot h oist them beyond the top o f the sh a ft even though he should fo rg et to stop the m achine or be incapacitated by heart trouble or other injury.
Ma y 1 9 ,1 9 2 7 C O A L A G E 723
H a rd n e ss a n d T o u g h n ess o f R ocks D e te rm in e d By V a rio u s E x p e rim e n ta l M ethods"
S p eed of D r illin g , P la c e m e n t o f H o le s and Q u a n tity and Q u a lity o f E x p lo s iv e U se d , Im p o rta n t F a c to r s in A ll M in in g O p eration s, C ould B e E stim a te d from R o ck T a b le s— Su ch D a ta W ill G rea tly H e lp E n g in eer:
By E m ile E. Gyss and Ilcn ry G. Davis
S c h o o l o f M in e s , C o l u m b i a U n i v e r s i t y , N e w Y o r k C i t y
I
M PO R TA N T FACTO RS in all m ining operations requiring the removal of rock are the speed o f drilling, the placem ent o f holes and the quality and quantity o f explosive used. T hese are functions of the hardness and tou gh n ess o f the rock and m ust be considered in com piling a table th at w ill
enable a m in in g engineer or operator to estim ate both drillin g speeds and the quantity o f dynam ite required in any given rock.
A s a result, the hardness o f a hom ogeneous rock m ay be described as its resistance to penetration by any agency, fo r ex
ample, by a steel drill bit.
In the sam e m anner, rock toughness m ay be defined as its resistan ce to d isin tegration or th e rupture of its co n stitu en t m inerals.
Rock hardness, as here de
fined, is a fu n ction of the im penetrability o f t h e component g ra in s as well as of th eir size and ar
rangem ent, and the nature o f the binding m aterials.
The tou gh n ess o f a rock is largely dependent upon , the sam e factors but is measured by an en tirely different m e t h o d . The hardness o f a rock is usu- ~
ally expressed in u nits th a t represent either relative values or alphabetical designations which have no definite q u an titative equivalent. Dr. Robert M. Ray- m ondf su g g e sts th at th e composite hardness o f rocks be m easured in term s of the hardness of th eir con
stitu en t m inerals based on M ohs’ scale. T his is done by m u ltip lyin g the percentage of each m ineral in any given rock by the Moh hai’dness o f th at mineral, add
ing th ese resu lts and dividing by 100. The values thus obtained convey a clear understanding o f rock hardness to the men interested or engaged in any kind o f rock work. Tables I and II are based on such units.
Rock hardness as variously defined m ay be deter
m ined in different w ays. One method, as indicated in the preceding paragraph, is that in which the
• A b s t r a c t o f a p a p e r e n t i t l e d " T h e H a r d n e s s a n d T o u g h n e s s o f R o c k s , ” p r e s e n t e d b e f o r e t h e m e e t i n g o f t h e A m e r i c a n I n s t i t u t e 01 M i n i n g a n d M e t a l l u r g i c a l E n g i n e e r s , N e w Y o r k C ity , F e b . 14
17> 1927- . C . n-
f P r o f e s s o r o f r a i n i n g e n g i n e e r i n g , S c h o o l o f M in e s , C o l u m b i a U n i v e r s i t y .
proportionate average o f the hardness of the com
ponent rock m inerals is taken as the basis of classifica
tion. Other factors, as the size, shape and arrangem ent of the grains and the tenaciousness of the binding minerals, are n ot considered. T his system has been
employed in the first col
umn of Table I. A s may be seen, there is a definite relation betw een the hard
ness so determ ined and the percentage of silica in the rock.
A second method, devel
oped by th e U. S. Depart- m e n t o f A griculture, X m easures rock hardness by the loss in w eig h t suffered by uniform ly-shaped speci
mens o f rock when held a gain st a revolving disk composed of g r a i n s o f quartz. The hardness of various rocks, as deter
m ined by th is test, is given in the first column of Table II. T hese values are obtained b y arbitrarily selectin g 20 as the hard
ness o f quartz and from th is deducting one-third o f the w eig h t lost by each m ineral specim en per 1,000 revolutions of the disk.
The second column o f Table II w as calculated from the Table I—Variation of Rock Hardness
With Silica Content*
H a rd n e ss B ased on P e r C e n t Silica
K in d of R ock M i
C h e r t ...
Q u a rtz ite ...
R h y o lite ...
G ra n ite ...
G ra n ite G n e iss...
B io tite G ra n ite ...
G ra n o D io rite ...
Q u a rtz M o n z o n ite ...
D a c it e ...
T r a c h y t e . ...
Q u a rtz D io rite ...
S y e n ite G n e iss ...
S y e n ite ...
P e rio d o tite .. ...
D io rite ... ...
A u g ite A n d é site ...
A n d ésite ... ...
G a b b ro ...
S a n d s to n e . ...
D io rite G n eiss ...
F e ld sp ath io Q u a rtz ite ...
B a s a lt...
D ia b a s e . ...
B io tite G n eiss...
G a b b ro G n eiss. . ...
H o rn e b le n d e G n e is s .. . P y ro x e n ite . ...
H o rn e b le n d e S c h is t...
B ito te S c h ist...
C alcareo u s S a n d s to n e ...
M ica S c h is t...
L im esto n e ...
M a r b le ...
* D a ta in th is ta b le co m p iled fro m IT. S. W ash in g to n , “ C h em ica l A nalysis of Ig n eo u s R o c k s,” U . S. G eological S u rv ey , P rofessional P a p e r N o. 99, a n d E . C. E . L o rd , “ R elatio n of M in eral C om p o sitio n a n d R o ck S tr u c tu re to th e P h y s ic a l P ro p ertie s of R o a d M a te ria l,”
U . S. D e p a rtm e n t of A g ric u ltu re B u lle tin No. 348.
C om position in Rock
6 .9 5 98
6 .63 95
6 .55 76
6. 54 74
6.51 73
6.4 9 71
6.4 0 70
6. 37 68
6.3 5 69
6.35 65
6.31 66
6.31 66
6.39 66
6.23 42
6.26 62
6.25 60
6. 17 62
6. 14 53
6. 13
6. II 58
6. 19
6.07 5(1
6.04 52
5.92
5.83 50
5.83
5.67 51
5.63 5.59 5.41 5 .29 3 .7 0 3.20
hardness value o f rhyolite given in the first column and from its corresponding value, 6.55, in Table I.
In these te sts abrasion is the critical factor that m easures hardness and the influence o f impact is negligible. A s the latter plays an im portant part in all drilling operations, the second method m easures rock hardness only in part. H owever, several authorities have considered such data the m ost sa tisfa cto ry from which to compile tables o f rock hardness.§
A third method of classification has been proposed by H arley.* D eterm inations o f rock hardness for under
ground opei’ations are made by the d rill-test method
I F r a n k H . J a c k s o n , J r . , “ M e t h o d s f o r t h e D e t e r m i n a t i o n o f t h e P h y s i c a l P r o p e r t i e s o f R o a d - B u i l d i n g R o c k , " U . S . D e p a r t m e n t o f A g r i c u l t u r e , B u l l e t i n N o . 3 47.
S N o ta b ly , W . O . S n e l l i n g in a p a p e r p r e s e n t e d b e f o r e t h e E n g i n e e r s S o c i e t y o f W e s t e r n P e n n s y l v a n i a : N . G . J . Y o u n g , E l e m e n t s o f M i n i n g ,” p. 98 ; a n d H . P . G i l l e t t e , " H a n d b o o k o f R o c k E x c a v a t i o n , " p. 4 39. S i n c e t h e s e t a b l e s w e r e p r e p a r e d , m a n y m o r e h a r d n e s s d e t e r m i n a t i o n s h a v e b e e n m a d e a n d t h e s e a r e i n c l u d e d i n T a b l e I I .
*G . T o w n s e n d H a r l e y , “ P r o p o s e d G r o u n d C l a s s i f i c a t i o n f o r M i n i n g P u r p o s e s . ” E n g in e e r in g a n d M i n i n g J o u r n a l , V o l. 1 2 8 , N o . 10.
S e p t 4 1 9 2 8 , p. 3 8 8 -3 7 2 , a n d V o l. 1 2 0 , N o . 11 , S e p t . 11 , lO Jfi.
t>. 4 1 3 -4 1 8 .
•724 C O A L A G E VOL.31, No.20
but, instead o f exp ressin g it as a fu n ction of th e drilling speed, the foot-pounds o f energy required to cut a unit volume (usually 1 cu.in.) o f rock from a drill hole is taken as a m easure of its penetrability. T h is m ethod elim inates those variables, such as type o f drill, air pres
sure and b it size, w hich e x is t in other te s ts o f th is type. The u n its used by H arley are alphabetic and, w ith ou t careful study, have but little m eaning. The h ard est rocks, or those requiring the g rea test energy to drill a hole of u n it volume, are classed as A -j-, A and A — . The so fte st rocks, or those requiring the le a st energy per unit volum e drilled, are classed as D -{-, D and D - . Rocks in term ediate in hardness betw een th ese groups are classed as B -\-, B, B — and C-\~, C, C .
A pplication o f th is nom enclature to different rocks, such as g ra n ites, syen ites, diabases, etc., is not indi
cated by Mr. H arley. W hether drill-speed or energy- volume m easurem ents are used in th is m ethod, th e com parative resu lts will be influenced by the age and condition o f the m achine, the kind o f drill steel used, the m ethod o f tem pering and the shape of the bit. As recommended by H arley, th e personal equation in drill
in g is largely elim inated by u sin g a vertical stoper drill.
A lthough Tables I and II are o f in terest, a more valuable classification could be obtained from compar
a tive d rilling speeds and energy consum ptions per unit volum e o f hole drilled. T hese data, on rocks o f d if
fere n t ty p es and classes, could' be obtained from m ine operators in variou s section s o f th e country. In order th a t te stin g conditions m ay be as uniform as possible, t h e follow in g recom m endations are m a d e : . Some
standard make of m achine drill should be used. Inger- soll-Rand rock drills are preferable as th ese m achines are w id ely d istributed and have been carefully tested on Quincy gran ite. A vertically operated stopper drill is b est as it elim in ates any variation s th a t m ay be intro
duced by the runner and also reduces the fr ictio n o f the b it on the side o f the hole.
The air p ressure should be kept constant at 80 or 90 lb. per sq.in. and the drill b it should have a double taper w ith a 90-deg. c u ttin g edge. The b its, preferably,
Table II—Mineral Hardness As Found by Various Methods*
H a rd n e ss in H a rd n e ss H a rd n e ss XI. S. D e p t of R ec a lc u lated from K in d of R o ck A g ric u ltu re U n i t s t to M o h s ’ S cale T a b le I C h e r t... ... 19.4 6 .9 5 6 .9 5 Q u a rtz ite ... 18.9 6 .7 7 6.6 3 H o rn e b le n d e G ra n ite ... 18.6 6 .6 7 . . . .
•F e ld sp a th ic Q u a rtz ite ... * 18.5 6 .6 3 6 .1 0 R h y o lite ... 18.3 6 .5 5 6 .5 5 G r a n ite ... 18.3 6 .5 5 6 .5 4 F r e s h D ia b a s e ... 18.3 6 .5 5 6 .0 4 A u g ite S y e n ite .. . . , ... 18.3 6 .5 5 . . . .
D io rite ... 18 .2 «
T r a c h y te ... 18.1 6 .4 8 6 .3 3 S y e n ite ... 18 .0 6 .4 5 6 .3 0 B io tite G r a n ite ... 17.9 6.41 6 .4 9 B a s a l t ... 17.8 6 .3 8 6 .0 9 G ra n ite G n eiss... 17. 7 6 .3 4 6.51 G a b b r o ... 17.7 6 .3 4 6 .1 4 H o rn e b le n d e G n eiss... 17.6 6 .3 0 5 .8 0 A m p h ib o iite ... 17.5 6 .2 7 5 .8 2 A n d e site ... ¡7 .0 6 .0 9 6 .1 7 H o rn e b le n d e S c h ist... 17.0 6 .0 9 5 .6 0 M ica S c h is t... ¡ 6 .9 6 .0 5 5 .2 0 B io tite G n e iss ... 6. 5 .9 5 5 .9 2 B io tite S c h is t... ¡6 .1 5 .7 7 5 .5 0 C alcareo u s S a n d s to n e ... 15.8 5 .6 6 5.41 C h lo rite S c h ist... 15.4 5 .5 2 --- S la te ... 5 -0 5 .5 8
D o lo m ite ... ¡ 4 .9 5 .3 4 . . . . F e ld s p a th ic S a n d s to n e ... ¡4 6 5 .2 3 . . . . S a n d s to n e ... 4 -4 5 .1 6 6 .1 3 P e rio d o tite ... 4 .2 5 .0 9 6 .2 8 L im esto n e ... ¡4 . J 5 .0 5 3 .7 0 M a r b le ... 13.1 4 .6 9 3 .2 0
* T h e d a t a g iv e n i n th is ta b le re p re s e n t a v e ra g e figures as d e te rm in e d from h u n d re d s o sp ecim en s of rocks classed u n d e r a n y o ne n am e. W ith le w exceptions, th e h a rd n e ss v alu es fro m T a b le I cheek fa irly closely w ith th o se p re sen te d h e re a n d w hich w ere o b ta in e d b y e n tire ly d ifferen t m eth o d s.
f U . S. D e p a r tm e n t of A g ric u ltu re B u lle tin N o . 348.
should be 13, 12 and IS in. in diam eter. The hole should first be collared to a depth of about 2 in., after which a new steel should be inserted and the m achine run fo r about one m inute. The depth and average diam eter o f the hole, as well as the exact tim e th a t the m achine w as in operation, should be determ ined so that both the drilling speed and th e energy required per unit volume o f rock penetrated could be calculated. F iv e to ten such te sts on each different kind o f rock w ould give resu lts th a t would be both helpful and useful. So th a t it m ay be properly classified, a com plete description of the rock, so fa r as possible, should also be given.
There are y e t a number o f variables in the method o f te st ju st described. H ow ever, by u sin g as new a m achine as possible, or one th a t has been recently over
hauled, the difference in en ergy betw een th at developed by new and old m achines will be greatly decreased. Steel tem pered by standard m ethods should largely elim inate th e variable hardness o f the drill bit.
Sh a p e a n d Co h e s i o n La r g e l y Fix To u g h n e s s
A table sh ow in g the relative toughness of rocks should also indicate the relative am ount and stren gth o f explo
sive required fo r breaking them m ost econom ically.
The tou gh n ess of a hom ogeneous rock is largely deter
m ined by th e shape and arrangem ent o f the component grain s and by th e ten a city o f the b in d in g m inerals.
H owever, the principal difficulty in com piling such a table lies in th e fa ct th a t rocks are not hom ogeneous, uniform , m assive and unaltered.
In addition, the character and proxim ity o f fra c
tures, bedding planes, slips and shear planes, as w ell as the degree o f alteration, w ill introduce fu rth er vari
ables in any se ries o f practical te sts designed to deter
mine, directly by a m ethod o f explosive consum ption, the tou gh n ess o f any given rock. The follow ing factors, in addition to rock toughness, w ill also influence the consum ption o f explosive per u n it o f m aterial broken:
(1 ) The stren g th and character o f the explosive; (2 ) the depth, size, number and orientation o f the holes;
(3 ) the desired size of the blasted product; and (4 ) the num ber o f free faces o f rock blasted.
In a rrivin g at approxim ate determ inations o f th e ex plosive en ergy required in b lasting, H arley* has taken som e o f th ese fa cto rs into account. H e has developed a relation betw een the power input o f a drill in cu ttin g a hole o f unit volum e and the effective explosive energy required to break a u n it volum e o f rock. The work done in both in stan ces is m easured by the reciprocal o f th e mean diam eter o f th e com m inuted rock. T h is is ex pressed by the eq u a tio n :
P ow er input o f drill
per cu.in. o f rock Reciprocal o f the m ean diam eter removed o f rock-drill cu ttin gs.
E ffective w ork o f — Reciprocal o f the mean diam eter e x p l o s i v e s per of pieces in th e ideal muck
cu.in. of r o c k pile broken
T his proportion is corrected by tw o factors. One is a fu n ction of the number of, and distance betw een, slips, shear planes and lines o f w eakness. The other is a tou gh n ess factor w hich is a fu n ction o f the structure, texture, and chem ical com position o f the rock.
A t p resent no such data as th is is available from which to com pile a rock table. H ow ever, an exten sive series of te sts on rock tou gh n ess, u sin g a P age im pact
•L o c . cit.
