COIVCRETT SOCIEIY" TECITrVICAL-?APIIR "IvO 1O5

F. A. Auld BSc, PhDictCflngi:,MIGE.t::,MIMi,f]E ;-;, iFFBC h i e f D e s i s n E n s i n e e r .

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Terminal House, Grosve,no.,_r:. Gardens3e LortdonrSWilW!{ OA,JI -".)t.;a.i lThe Conc re te Soc ie t y ,

The author wlshes to thank Mr J C Black, ManaglngDirector of Cenentat ion Hlnlng Lin l ted, forpernisslon to present the paper. I l lustrat lons anddetal ls are inc luded f ron the Selby New MineProjecc and the author ls lndebted toMr C T Massey, Deputy Dlrector ( l { in ing) - SelbyProject , of the Nat lonal Coal Board for h ispernisslon to use th ls lnfornat ion.

Further acknowledgenents are due to Mr V W l lowe,who was responslble for producLng nany of thei l l u sc ra r i on d raw lngs , Cemen ta t l on M ln l ng L lm i t ed rsdrawlng of f lce personnel for assistance lndetai l ing others, Mrs J Slmpson for prLntLng chei l lustrat lons, Mrs M Mordue for typlng themanuscr ipt , and var ious col leagues in Cenentat ionMlnlng Lin i ted for supply ing the photographs.

Fronc cover photograph: Typical shaf t bot ton showingactual worklng condi tLons. Mount Isa Copper Mine,sha f t A .10 .S , Aus t ra l i a .

Concrete Soclety Technical Paper.No. 105

Flrst publ lshed 1983 -

ISBN O 72LO T284 I

Publlshed by The Concrete SocletyTerninal House, Grosvencir Gardens, London SWIW OAJ

Designed and prlnted by the Cement and ConcreteAssociat ionWexhan Springs, Slough SL3 6PL

Further copl-es nay be obtained fron:Publ lcat lons Dlstr lbut lon, CeEent and ConcreteAssocl .at ionI{exham $prlngs, Slough SL3 6PLquot lng' reference nunber 53.039

Price Group CS5

@ fne Conc re te Soc te t y 1983

Although The Concrece Soclety ( l in l ted byguarantee) does l ts best Eo ensure Ehat any advice,recoomendat ion or lnfornat . ion i t nay glve el ther Lnthis publ lcat lon or e lsewhere is accurate, nol l ab l l l t y o r r espons ib i l i t y o f any k i nd ( t nc l ud ingl tabl l l ty for negl lg6nbe), howsoever and f ronl thaEsoever cause ar is lng, ls accepted ln th isrespec t by t he Soc le t y , l t s se r van t s o r agenEs .

Goncrete inUnde$rorrnd.IllorlcsF. A. Auld BSc, PhD, CEng, MICE, MIMinE, FFBChief Design Engl-neer ,Cenentat ion Mln ing L in i ted

Paper p resented a t The Concre te Soc ie tyYorkshire and Hunberside Reglon.One-day Synposlun, Concrete in power andenergy . Se lby Fork Hote l , Yorksh i re

18 Novernber 1981

The paper covers three aspects ofconcret ing in underground works.

I n t he f i r s t sec t i on , va r i ous t ypes o fs t ruc tu re a re desc r i bed to i l l us t ra tethe broad range of concreteconstruct ion work which is involved inmining development . An indicat lon ofgene ra l des ign p r i nc ip les i s a l soinc luded .

The secbnd sec t i on i l l us t ra tes t hemeans of carry lng out the work. Plantand cons t ruc t i on t echn iques a redesc r l bed i n de ta l l .

A d i scuss ion on m ix des ign requ i remen tscons t l t u tes t he th i rd aspec t . I nc ludedin th is sect ion are commenE.s on the useof cement replacement mater ia ls andadmix tu res .

eutfror's Introductorywote onRecent and.GurrentUndeground.Worlcs ProjectsCenentat lon Mlnlng Lin l ted have ln the last f iveyears been lnvolved ln the conscruct lon of s ixsha f t s ( ou t o f a t o t a l o f t en ) and t so d r i f t s f o rthe Nat lonal Coal Board's New Mlne ProJect at Selbyl n Yo rksh l r e ( see F igu re 1 ) . Sha f t dep ths rangefrom 417 to 1033 n. The Gascolgne Wood dr l f ts andlwo shaf ts at WlsEow are norr complete, wi th theother four shaf ts, cwo at Rlccal l and two ar NorthSe lby , s t l l l unde r cons t ruc t l on a t t he p resen tt loe. AI I the shafEs at Selby have been sunk uslngthe f r eez lng p rocess t o con t ro l wa te r , t he dep thsof f reeze ranging f ron 148 to 283 n. Cenentat ionMlning Lin i ted are also ready to conmence s inklng,w i t hou t f r eez lng , a new 1023 ro deep sha f t a t Ma l t byCo l l i e r y f o r t he NCB.

Du r i ng t he pe r i od 1963 t o 1973 , e i gh t sha f t s we resunk for Ehe potash nines ln Saskatchewan, Canada,by The CeEen ta t l on Co . (Canada ) L td . , s l x o f t hento dep ths o f ove r 1000 n n i t h f r eeze dep ths f r om468 t o 684 n . Many o the r sha f t s have been sunkove r t he l as t lwen t y yea rs t n va r i ous coun t r l esw iEh o r s i t hou t f r eez lng . I n Ge rnany , s i x t eenshafts have been sunk dur ing the per lod using thef reez ing p focess , f ou r o f t he@ cu r ren tcon t rac t s 1 . A t o ta l o f t h i r t y -one sha f t s havebeen constructed in Canada and Norrh Aoer ica s lnce1963 uslng f teezlng 2. The Chinese have also sunkr n o r e t h a n s e v e n t y s h a f t s , a l l f r o z e n 3 .

Annua l l eng ths o f 56 and 47 .3 ko a re quoced f o rl l ned and un l i ned t unne l s f o r t he yea rs 1979 and1980 respec t l ve l y a . Du r i ng t he l as t f i f t een yea rsCeEentat ion Mlning LiEi ted have been theconEractors for che Alcan Snel ter polrer staEioncoo l l ng wa te r i n t ake and ou t f a l l t unne l s a tLynenouth, the two Is le of Grain pouer sta i ioncool lng sater lntake tunnels and the s inglePeterhead power stat ion cool ing water intaketunne l . I n 1978 t hey a l so comp le ted t he Ed inbu rghe f f l uen t ouc fa l l t unne l w iEh twen t y d l f f use rs ! othe sea bed ln Seaf le ld Bay. At leasE two noresuch con t rac t s a re cu r ren t l y l n p rog ress by o the rc o n t r a c t o r s .

The f u tu re po ten t i a l f o r sha f t , t unne l andunderground construct lon is enormous. Access belowg round l s r equ i r ed f o r nany pu rposes : e .g :

n i ne ra l ex t r ac t i on ;power s t a t i on and assoc la ted f ac i l l t i e s ( coo l i ngwa te r t unne l s and nach lne ry ha l l s ) ;e f f l uen t r eoova l t o t he sea ;s t o r a g e ( g a s , l i q u i d o r n u c l e a r w a s t e ) ;nuc lea r she l t e r s .

Al though aE the present t lne the wor ld-vLdeeconornic c l lnate is no! favourable for suchdeve lopoen t , nany f u ru re na jo r p ro j ecEs a rei nev l t ab le .

F A AuIdOc tobe r 1982

References[ . KLE IN , J . P reaen t 6 ta te o f f r eeze sha f t des lgn

ln n ln lng. Proc. of the Synposiun on StrataMechanlcs, Univers i ty of Newcast le upon Tyne, 5-7 Ap r l 1 , 1982 . E l sev le r Sc ien t l f l c Pub l l sh l ngConpany , 1982 . pp . 147 -153 .

BRAUN, B. and NASII , W.R. Ground f reezLngappl icat lons ln underground nin lngcons t ruc t l on . P roc . o f The Th i r d I n te rna t l ona lSynposiuro on Ground Freezlng. US Arruy Corps ofEngineers Cold Reglons Research and Engln-eer ingLabo ra to r y , Hanove r , New Hampsh l re , USA . 22 -24J u n e , 1 9 8 2 . p p . 3 1 9 - 3 2 6 .

AULD, F.A. Notes on v is l t of Cementat ion MlnlngLlnl ted/Foraky Lln i ted Technlcal Delegat lon toC h i n a , 3 - 1 5 O c t o b e r , 1 9 7 9 .

CONSTRUCTION INDUSTRY RESEARCH AND INFORMATIONASSOCIAT ION. R .P . 307 - P ipe Jack ing Phase 1 .Second Draf t Report . Chapcers 1, 2 and 3 andAppend i x A , B , and C . Ap r i l , 1982 .

4 ,

Gontents

I.IntroductionaIVI,es of Stnrcture and.

Generaf Desi$n FinciBles 4In t roduct ion

Sha f t s

2 .2 . I Advan tages o f conc re te i nshaf t construct ion

2 .2 .2 Re in fo rcemen t2 . 2 . 3 D e s i g n o f s h a f t l i n i n g s

2.3 Co l la rs and fo reshaf ts

2 .4 A i r and fan dr i f t s

2 . 5 I n s e t s

2 . 6 T u n n e l s

2 .7 Sp i ra l chu te bunker shaf ts

2.8 Sump tanks

2 . 9 P l u g s

4

6

2. r2 . 2

4. Goncrete llltix Design4 . 1 I n t r o d u c t i o n

4.2 Normal mixes

4.3 Cement rep lacement mater ia ls

4 .4 Admix tu res

5. Gonclud.lng Remarks6. Eeferences

666

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2B

2B

292929

30

30

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3 l

3 l

3 3

3 4

5. Construction MetJrod.s3.1 In t roduc t ion

3.2 Co l la rs and fo reshaf ts

3 .3 A i r and fan dr i f t s

3 .4 Shaf t l in ing

3 . 5 I n s e t s

3 .6 Tunne ls

3.7 Spiral chute bunker shafts

3.8 Sump tanks and plugs

3.9 Batch ing p lan t

3 .10 Transpor ta t ion and p lac ing

3.10 .1 Transpor ta tLon down shaf ts3 .10 .2 Transpor t underground3.10 .3 Concre te p lac ing a t roo f leve l

Page

4

7. GlossarJr of llfiining Terms :s

l.IntrodustionConcrete and steel are the two najor construcElonnater la ls used in underground developnenc work.Steel ls nornal ly enployed ln the forn of arches orsquare work (colunns and beans), fabr l .cated f ronstandard secElons. Archee or square sets roay beused as pen0anent support to an excavat lon or astemporary supporE prLor to provld ing a peroanenEconcrete structure. Except in extrenely competentand sel f support lng ground, or Ln ground whlch canbe supported by rock bol ts and nesh, steelworkcenpo ra ry suppo r t , p r l o r Eo l l n i ng l n conc re te , l sessen t i a l f o r sa fe wo rk i ng 1n unde rg roundexcava t i ons .

UsLng concrete underground creates addl t lonalproblens to Ehose encountered above ground,

Conf lned spaces present access, handl lng andpJ.acing problens and. for developnent sork inex l sE lng p i t s , i t s use ous t no t i n t e r f e re w l t h p l tp roduc t l on . Neve r t he less , wLch a co r rec l l yenglneered handl ing systen, the r lght p lant and asulEable nlx deslgn, concrecLng underground Ls noEd i f f i c u l t .

Thls paper concentrates on three naLn aspecte ofunde rg round cons t ruc t l on w i t h conc re te . F l r s t l y ,l t i l lustrates the types of sf ructure which can befound ln such an envlronnent. Also lncluded aregene ra l des lgn p r l nc l p l es f o r such s t r ucL . l r f es . Thesecond sec t i on desc r l bes how cons t rucB lon wo rk o ft h l s k i nd i s ca r r i ed ou t . F l na1 l y , conc re te D l xdes lgn requ i r enen t s a re l nd l ca ted . I n che l a t t e rsecl lorr , the use of cenent replacement Eater la lsand adnlxt .ures ls conmented uDon.

a IIrI,es of Stnrcture and, @neral Desilfn Pr'rnciples2 . 1 I n t r o d u c t l o n

In s inple terms, underground development workl nvo l ves ch ree d i s t i ncc s tages o f ope ra t l on ( seeF igu re l ) . Fo r a new n ine , t he f i r s t s t age l s t hesinklng of a shaf t or an lncl lned dr i f t to reachthe level of the proposed undergrounddeve lopnen t . Second l y , ho r i zon ta l o r nea r l yho r l zon ta l t unne l s a re d r l ven Eo t he ex t r ac t l onface o f t he o re body . Th l r d l y , pa r t l cu l a r a reasalong the dr ivage are enlarged to house equipoentand o the r p roduc t l on f ac i l l t i e s . The cons t ruc t l ono f o the r unde rg round s t r uc tu res wh i ch a re r equ i r edi s a l so l nc l uded i n t h i s l as t sEage . F i gu re 2shows nany of the structures to be found ln a n lne.

Civ l I englneer lng shaf t s inking and tunnel l lng worki s ca r r l ed ou t i n s i n l l a r s t ages t o t ha t f o r a newmlne . Ex i s t l ng p l t deve lopnen t l s pu re l y anex tens lon o f f ac l l i t l e s on t he saoe bas i s .

F i i u r e 1 .

4

To put the use of concrete underground lntoperspect ive, i ! t rust be reroeobered Ehat the nln ingenv i r onmen t f t nposes l t s own spec ia l cond i t l ons .A l l i ed r l l t h any excava t i on l s a cons lde ra t l on o ftwo naJo r f ac l o r s :

( a ) The s tab l l i t y o f t he excava t l on once l t i sopened up ,

(b ) The poss ib l e p resence o f waEe r l n l a rgeq u a n t i t i e s .

Eo th o f t hese aspec t s can be s tud ted p r l o r Eoexcava t i on , us i ng geo log l ca l and hyd rogeo log l ca lbo reho le da ta , and t he t r e thod o f g round p re -t r ea tnen t can be es rab l l shed . P rov l ded t he wa le ri n f l ow i s l ow l t can be hand led en t i r e l y by d l r ec tpunp ing o r w l t h t he ass l s t ance o f a we l l dewa te r l ngs c h e m e .

I f t he s tud ies i nd i ca te t he p resence o f l a rgequan t l t i e s o f l r a t e r , t hen p re - t r ea toen t by g rou t i ng

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F igu re 2 . M ine s t r uc tu res and ope raE iona l f ac i l i t i e s .

t ray be necessary to reduce the Lrater nake lnto thee x c a v a t l o n . G r o u t l n g l s t h e p r o c e s s o f l n j e c t i n gc e m e n t , o r o t h e r m a t e r i a l s , t o i o p r o v e t h e s t r e n g t ho f t he s t r a te o r t o r e ta rd o r p reven t t he passageo f l i q u i d s o r g a s e s . F o r e x c e s s l v e a n o u n t s o fwa te r l n cond i t i ons whe re t he g round i s no tsuscep t i b l e t o g rou t i ng , f r eez ing t echn iques can becons ide red . The f r eez lng p rocess i s a l onges tab l l shed me thod o f conso l i da t l ng wa te r -bea r i ngs t ra ta t o p repa re i t f o r sha f t s i nk i ng , l n wh i ch af r eez ing agen t ( usua l1y b r l ne ) i s c i r cu l a tedt h r o u g h s u i E a b l y d i s p o s e d b o r e h o l e s d r i l l e d i n t othe s t r a ra a round t he s i t e o f t he sha f t . S i t r l l a rt echn lques can a l so be emp loyed i n t he ho r i zon ta ld i r e c ! i o n f o r t u n n e l s .

I t ls l r iEhin th ls envlronnent that concrete must betransported and placed underground. Ful l knowledge1s t he re fo re essenE ia l o f t he behav lou r o f conc re tel n a l l ch ree phases o f 1 t s i ns ta l l a t i on , l n f he weEsEa te r du r i ng l n i t i a l se t t l ng and i n t he f u l l yha rdened cond i t Lon .

The Eethod of excavat ing is an added factor to beconsLde red when us l ng conc re te unde rg round .B las t l ng i s no rna l l y e rnp loy i d and i t s e f f ec t s onear ly age concrete at c lose range EusE beacconnoda ted . The sub jec t o f b l asc i ng e f f ec r s onear ly age concrete ls a conplex one and lst he re fo re ou t s i de t he scope o f t h t s pape r .

I n add iC ion t o g round t r ea tmen t , t he l i n i ng o f anexcavat ion can also be designed pr ior tocons t rucE ion by enp loy i ng . rock and so i l mechan l csp r l nc l p l es Eo de te rn i ne g round p ressu res o r on t hebas l s o f t he l i n i ng rs ab l l iEy t o r es l s t hyd ros ta t i cp ressu re . Conc re te l i n l ngs i n t h l s con tex t cane i t he r be pu re l y cosne t l c whe re l he g round i s se l f -suppo r t l ng ; t hey nay be cons t ruc ted a f t e rl nsca l l l ng s tee lwo rk t empo ra ry suppo r t ; o r t hedes ign cou ld necess i t a te r ap id l ns ta l l a t i on ,lnnediately upon openlng up the excavat ion, tonln in ize ground movement.

2 . 2 S h a f t s

A t yp l ca l sha f t sec t l on i s i l l u s t r a ted i n F i gu re 3 ,t oge the r w i t h t he geo logy and esE lmaEed wa te rlnf lows needed for ground pre- t reatment analysisand sha f t l i n l ng des lgn .

2 . 2 . 1 A d v a n t a g e s o f c o n c r e t e i n s h a f tcons t ruc t i on

The cho i ce o f conc re te as a sha f t L i n i ng ma te r i a li s eas i l y Jus t l f l ed . Re la t i ve l y sma l l a reas o fwa l l can be cons t ruc ted sys tema t l ca l l y i n phasew l t h t he sha f t s l nk l ng p rocess . T ranspo r t t o anypos i t l on i n Ehe sha f t i s s l np le by neans o fp i pe l l ne o r sk i p . Conc re te i s a conven len tnaterLal to handle and place r . r1 lh in fhe restr ic tedwork l ng space o f a o l ne sha f t . When p l aced ,conc re te mou lds i t se l f t o Che excava ted p ro f i l e o fthe shafE provld ing an inEer locking act ion wi th thesu r round ing rock . TesE ing p rocedu res f o r conc re tequa l i t y con t ro l a re s t r a i gh t f o rwa rd . Res i s t ance t osulphate at tack is achieved by using sulphateres i s t i ng Po r t l and cenen t , p roduc ing a s t r uc tu rewh l ch requ i r es l i t t l e na in tenance .

Un re ln fo r ced conc re te can w l t hs tand mos t l oad ingcond i t l ons no roa l l y encoun te red and 1 t p roduces ad ry ' sha f t . T t r e bene f i t s o f us i ng conc re te ,pa r t l cu l a r l y un re i n fo r ced conc re te , f o r sha f tI i n l ngs a re t he re fo re subs tan t i a l .

2 . 2 . 2 R e i n f o r c e m e n tSEee l r e l " n fo r cemen t i s used on l y l n spec ta lc l r cuns tances , whe re weak s t r a ta occu r , t o p rov i deres l s t ance t o l oca l i sed t ens l l e bend ing s t r essesand as a means o f p reven t i ng f r agmen ta t l on o f t heconc re te , Howeve r , s t ee l r e i n fo r cenen t wh i ch hasCo be included ln a shaf t wal1 could be subject toco r ros i on wh l ch cou ld cause spa l l l ng . I n add i c i on ,t .here is a probleo ln f ix ing the re lnforcement and

so , l n gene ra l , i t l s p re fe rab le t o useun re ln fo r ced conc re te .

2 . 2 . 3 D e s i g n o f s h a f t l i n l n g sThe des lgn o f conc re te sha f t l i n i ngs i s d i scussedroo re f u l 1y i n o the r pape rs r , z . S t r esses i n ath lck cyl lnder can be deternlned eicher on ane las t l c des ign bas i s o r by an u l t i na te l i n l t s t a teapp roach eop loy i ng p l as t l c l c y p r i nc i p l es . I n Ehecase of a shaf t ln conpetenE (sel f s tanding whenexcavated) rock, the deslgrr of the l ln ing need onlyca te r f o r hyd ros ta t l c p ressu re t h rough t he aqu i f e rzones . The t h l ckness o f t he l l n l ng i s t he re fo revar ied wi th depth unt i l a level ls reached at whichsater is no longer present and only a noninalt h l ckness o f conc re te becones necessa ry . M lg ra t l onof wacer downsards f ron the hydrostat ic sect lon lsp reven ted by l ns ta l l l ng g rouc sea l s a t t he ' bo tEono f t he hyd ros ta t l c l l n l ng . I n g round wh i ch l slncompetent , rock pressures may need to becons lde red as an a l t e rna t l ve t o hvd ros ta t i c

P res su re .

The mlninun th ickness for a concrete shaf t l in lngls norual ly 300 nn unless che concrete is belngcas t . d l r ec t l y aga lns t f r ozen g round , l n sh i ch case600 oo should be the mlnLroun. Wlth th ls extrath i ckness o f conc rece su f f l c i enc hea t i s gene ra tedby the hydrat lon of Ehe cenent to overcome anyde t r l oen ta l e f f ec t s due t o f r eez ing o f t heconc re te . I nc renen t s o f wa1 I t h i c kness o f 150 nmare gene ra l l y used , up t o a nax lnum o f 1200 m , a twh i ch t h l ckness cons t ruc t l on beconeslnp rac t l cab le . Spec l f i ed cha rac te r i s t i c s r r eng thsfo r sha f t l i n l ng conc re te r ange f r om 25 N /mm2,sh l ch i s che l ose r l im i t f o r dense , wa te r t i gh t ,s t r uc tu ra l conc reEe , up t o 45 N /mn2 , t h l s be ing t hep racE i cab le uppe r l l n i t bea r i ng i n u r t nd t hecon f l ned cond l t i ons o f p l ac i ng . Howeve r , w iEhapp rop r i aEe n i x i ng red iencs and by us i ngworkab l l l t y agen t s and good qua l l t y con t ro l ,sE reng ths g rea te r t han 45 N /nu rz a re poss ib l e .

L in ing of the shaf t takes place downwards in 6 mleng ths as s l nk l ng p roceeds . PVC g rou t sea l s(F lgu re 3 ) a re p rov i ded a t each cons t ruc t i on j o i n tand coup le te na te r t i gh tness l s ach ieved us i ng abackwa l l g rou t i ng p rocess . F ron F igu re 3 i t cana l so be seen t ha t a t each ho r i zon ta l j o i n t i n anyf r o z e n s e c t l o n a s l o t i s l e f E a t t h e i n s i d e f a c ewhich can be gunl ted af ter conplet lon of heavedu r l ng Ehe f r eez ing pe r i od . Gun i t i ng i s ca r r i edout f tnmediately the cenperaEure of the l ln lng r lsesabove 0"C in the thawing per iod. The cr ibs shownln F igu re 3 p rov i de add i t l ona l suppo r t f o r t heseight of the l in ing Ehrough sof ter zones butnorrnal ly the weight is assumed to be t ransferredd i r ec t l y t o t he su r round ing rock .

2 .3 Co l l a r s and fo resha f t s

Pos i t l oned aE t he t op o f t he sha f t l l n l ng l s t heco l l a r and f o resha f t s t r uc tu re ( see F igu re 3 ) .Th i s i s cons t ruc ted i n r e l n fo r ced conc re te ( seeF igu re 4 ) . The t o ta l l eng th o f Eh l s sec t i on , f r oocol lar level to the bot ton of foreshaft wi l l varydepend ing upon t he g round cond iE ions . Wa l1th l cknesses a re no rma l l y g rea te r t han f o r t heuppe r sec t l ons o f t he sha f t l i n i ng . F i gu re 5 l sa v le l r looking down a f in ished col lar andfo resha f t .

The pu rpose o f t he co l l a r and f o resha f t l stwo fo l d . I t s ma ln f unc t i on l s t o p rov l de a r i g i d ,I oad ca r r y i ng s t r ucCu re wh l ch passes t h rough t heso f t , su r f ace so i l depos l t s and t r ans fe r s t hehead f rame and o the r co l l a r l oads t o t he ha rd ,conpe ten t r ock be low . I n o the r wo rds i t pe r f o rmsthe f uncE ion o f a l a rge d l ame te r p l l e . Theseconda ry f unc t i on o f t he co l l a r and f o resha f ts e c t i o n i s t o g i v e s u f f i c l e n t i n i t i a l d e p t h o fsha f t co enab le t he i ns ta l l a t i on o f t he s l nk i ngs tage t o be ca r r i ed ou t p r i o r t o t he Ea lnexcava t i on .

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F igu re 4 . Co l l a r and f o resha fE s t r uccu re w i t h f an d r i f t en t r y , Se lby R i ca l - l No ' . 2 ( upcas t ) sha f t .

In addl t lon to belng able to wi thstand al l lnposedloads , bo th ve r t l ca l and ho r i zon ta l , a t co l l a rl eve l , t he co l l a r and f o resha f t a re des igned t ores i s t g round and wa te r p ressu res ac r i ng rad la l l yon t he s t r uc tu re , wh i ch l nc rease w i t h depEh . Thec r i b s i t ua ted a t t he base o f che f o resha f t ass i s t sl n sp read ing t he ve r t i ca l l oad a t t h i s l eve l ove r al a rge r a rea , r educ ing t he bea r i ng p ressu re , as we l las p rov i d l ng an add l t i ona l key l n t o Ehe s t r a ta .

2 .4 L f t and fan d r i f t s

Hine ven t l l a t l on l s a ve r y i npo r t an t aspec t o funde rg round ope ra t l ons . No rma l l y sha f t s a re sunkin pa l r s , one f o r r n l ne ra l w ind ing and t he o the r f o rnen and oa te r l a l s access . As a seconda ry f unc t i on ,

8

ter ln shaf ts a l low one Eo be used for a i r entry andthe second for a i r exhausE. Entry and rernoval ofa l r nay t ake p l ace t h rough t he head f rane bu l l d i ng ,founded at col lar l -evel , or v l .a an incl , lned dr l f tw i t h a s l de en t r y i n t o l he co l l a r and f o resha f ts t r uc tu re be low g round l eve l . F l gu re 6 i l l u sE ra tesa re i n fo r ced conc re re exhaus t f an d r i f t f o r a sha f ti n wh l ch t he a i r Ls upcas t . A s l n l l a r s t r uc tu re ,l e rned an a i r d r i f t , wou ld be p rov l ded f o r a l ren t r y t o t he downcas t sha f t .

The des ign o f a i r and f an d r l f t s f o l l ows s tanda rdbasLc p rLnc lp l es . S ince one end i s a t t ached t o ar i g l d f oundaE lon - t he sha f t - s l n i l a r suppo r t mus tbe provlded over the reoainder of the dr i f tl engEh . The re fo re l n a l l cases o the r r han ha rdrock p l l ed f ounda t l ons a re necessa ry .

F igu re 5 .

Design is based on the analysis of the box cross-secE ion t o r es i s t su r cha rge l oads , ove rbu rdenpressures and lateral ground pressures togetherwl th any loads f ron surface structures founded ontop o f t he d r l f t . Sec t i on C -C o f F i gu re 6indlcates that Ehe s ide wal ls of the fan dr i f t havebeen deslgned as deep beams over Ehe sDan becweenEhe shaf t and cencral p l le cap to acconmodaEe heavyfounda t l on l oads f r on su r f ace s t r uc l u res .

ConsEruct ion sequences should be taken account ofl n des lgn . The ab l l i t y o f t he d r i fE t o ac t as aEhree 6pan beam ln l ts f inal condi t ion nay need to

r { i t h f an d r i f t en t r y

be augroented by an lnvest lgat lon lnto the part lycons t ruc ted s ta te o f a s i ng le span w i t h acan tL l eve r sec t l on ove r t he cenEra l p i l e cap . Thela t t e r cond l t Lon i s o f pa r t l cu l a r impo r tance i n Ehecase of a shaf t sunk in f rozen ground. ConnecElonof the dr l f t Eo the shaf t should only be made afcerDost of the ground set t lement dur lng thawlng hastaken place.

Air and fan dr i f ts are noE fu l ly undergroundstructures ln the t rue sense, but they are ofpart lcular importance ln that Ehey forrn anlncerface bel l reen the underground and Ehe surface

V iew down se lby w i s to r . / No . 2 ( upcas t ) sha f t co l l a r and f o resha f t s t r uc tu reE o t h e r i g h t .

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works . As such , t hey a re no t s l np le Eo cons t ruc t ,requir lng the correct tenporary works approach,conbinlng both c iv i l englneer ing and rn ln ingtechn lques . Connec t l on t o r he sha f t t akes p l ace a ta po ln t whe re g round s tab l l i t y l s poo r and g roundwater lngress lnto Ehe excavat lon is l lkely. Henceevery atEeDpt should be nade ln the deslgn tos i np l i f y t he sha fE rouCh ing deEa i l and t o p rov l dethe su r f ace wo rks s t r uc tu res w l t h f ounda t i onsindependen t o f t he a i r and f an d r i . f t s .

2 . 5 I n s e t s

Havlng sunk and l - ined a vert lcal shaf t l t isnecessary to dr lve away hor lzontal ly f ron thebo t t on . The s t r uc tu re wh i ch l s cons t ruc ted a ! t hep l t bo t t on t haE enab les t h i s wo rk t o p roceed l s t helnse t ( see F lgu re 7 ) . F i gu re 8 i s a v l ew o f are l n fo r ced conc re te l nse t unde r cons t ruc t l on . Thefunct lons of rhe lnset ln a worklng mine are top rov i de sk l p l oad tng f ac l l i t i e s f o r p roduc t i onw lnd ing and t r ans fe r l nsca l l a t i ons f o r oen andna te r i a l s . I c a l so p l ays an l npo r t an t pa r t l n t hen ine ven t i l a t i on scheee .

Des lgn p r l nc l p l es f o r l nse t s encon rpass two d l s t i nc tapp roaches as t r ans fe r f r on t he ve r t i ca l d i r ec t l onto t he ho r i zon ta l i s acconp l l shed . Sha f t I l n l ngdeslgn nornal ly involves a uni forn loading aroundthe c i r cun fe rence , ac t i ng l n a r ad ia l d i r ecE ion ,wh i ch c rea tes a co rnp ress i ve s t r ess w l t hou t bend lngon a c l r cu l a r shape . W i t h a t unne l , depend ing uponthe overburden pressure and the deformat ioncha rec te r i s t l c s o f t he rock , l a t e ra l p ressu res naybe d i f f e ren t f r on t he ve rE i ca l ones and bend ingloomenEs and shear forces are lnduced in a c l rcularp ro f l l e unde r Ehese c i r cumscances . I n f ac t , f o rthe rectangular and haunched arch prof i les shown inFigure 7, bendlng moments and shear forces arepresen! whether the loading ls uni forn al l round orno t . Howeve r , Ehe i r nagn lEudes cou ld changedepending upon lhe rat io bet \ reen the vert lcal andla te ra l p ressu res . Desp i t e t h i s p rob len , p rov l ded

both the shaf t neck r lng and the hor izontal roadwaysec t i ons a re des lgned l n acco rdance n l ! h t he l r ownp r i nc l p l es , t hen f r on expe r l ence l -E wou ld appea rthat the lnterconnecl ion between the two Eakes careo f i t s e l f .

One o f t he nos t d l f f l cu l t aspec t s o f l nse t des ignl s t o de te ro l ne accu ra te l y wha t t he t r ue l oad ingshould be. In nany cases ru le of thunb nethodshave been enployed, based on local knowledge andscapda rd p rac t l ce i n pa r l l cu l a r n l n l ng a rees .F i g u r e s o f ^ 1 3 . 4 , 2 6 . 7 a n d , 5 3 . 5 k N / n 2 ( L / 8 , I l 4 a n dl / 2 t on / f . t z r espec t i ve l y ) we re t he no rn un t l lr ecen t l y when t he va lues have r i sen Eo 106 .9 t o2 1 3 . 8 k N / n 2 ( l t o 2 t o n s / f t 2 ) . A p p l l c a t i o n o f t h l sl oad ing has t ended t o be on a un l f o rn l y d i s t r i bu tedbas l s a I1 r ound , a l t hough i n sone l ns taccps va lueso f 106 .9 kN /nz ( I t o r . / fEz ) have been t aken on t heroo f w i t h 53 .5 kN /n2 (L /2 t o t / f t 2 ) app l i ed ro r heve r t i ca l s i des . No appa ren t l og i c acconpan les t h l sme thod o f l oad de te rm lna t i on excep t Eha t l f t hesame i n tens l t y o f l oad ing has been enp loyed t odes ign ano the r s t r uc tu re o f t h i s t ype i n a s l . o l l a rm in i ng a rea e r l t hou t de t r i nenEa l e f f ec t s , t heconc lus l on has been t ha t i t nus t be sa t i s f ac t . o r y .Gene ra l l y t h i s p r i nc i p l e ho lds t r ue l f l he g roundis conpetent but in a ru le of thunb approach thet rue f ac to r o f sa fe t y l n t he des ign rena insunknovn . Whe re t he g round i s l nconpe ten t , hoseve r , .t he chances o f s t r uc tu ra l f a l l u re becone ve rv r ea lwhen us l ng t h l s me thod .

F o r g o o d d e s i g n , t h e r e f o r e , 1 t l s i n p e r a t l v e t ohave a mo re reaL i s t i c app roach t o t he eva lua t i on o ft h e i n s e t l o a d i n g . I n t h i s r e s p e c t , p a r t l c u l a r l yw i t h t he s iE ing o f s t r uc tu res i n coa l neasu ress t ra ta , t he wo rk ca r r i ed ou t by t he NCB M in lngResea rch and Deve lopmen t EsEab l l shnen t . a t B recby l nE n g l a n d h a s b e e n h e l p f u l 3 . U s t n g [ . l l l s o n ' s m e t i o do f des ign , t he c l osu re o f an unde rg round d r l vage i nweak rock can be re l a ted co t he l i n l ng s t r eng th andthe rock propert ies obtained f rorn laboratorytes t s . I n t h i s way , a l l n l ng can be p rov l ded wh l ch

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F i g u r e 7 .

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ls conpat ib le wi .ch the surrounding strata, and s i tha knorm factor of aafety. I t should be noted,however, that s i t lng of an lnseE relat lve to thecoal seam ls of partLcular lnportance andpreference should be glven to locaELons above andbelos the sof ter rocks assoclated wi th rhe mLneralbody .

once the t rue lnset loading ls establ ished, i t ls arelat ively s inple nat ter to determlne the bendlngnonent6 and shear forces for typical cro6s-sect lonssuch as SecElons A-A and B-B shoun ln Figure 7.The use of a conputer, for which standardstructural engineer ing prograns are avai lable,nakes Ehe analysls easler . In the analysls of thesEructurer account musE be taken of Ehe resistanceto def lexion of the surrounding rock. The correctdefornat lon propertLes of the ground need to beintroduced into Ehe program as spr lng sci f fnesses,as the surrounding rock rnodl f ies the bendingmonents and shear forces that r rould occur l f EhestrucEure were to be considered as unconf ined.

2.6 Tunne ls

Baslc pr incip les for tunnel l in ing design have beentouched on br ief ly in the previous sect ion oninseEs . Th i s i s no t su rp r i s i ng as t he ho r l zonEa lsect ion of an lnset ls s inply a Eunnel . The addedconp l i ca t l on i n Ehe case o f t he i nse t l s t hei nEe rconnec t i on w l t h t he sha f t . As w i t h Ehe i nse t ,t he ' sec re t t o f good t unne l l i n l ng des ign i s t oprovide a system shich is conpat ib le wiEh thesurrounding ground. This means natching up thedefornat lon characEer lst ics of the ground and thel i n i ng .

To fu l ! ,y understand Ehe role of concrete in tunnell l n i ng des ign , i t i s necessa ry t o be f an i l l a r w l t htunnel deslgn and construct ion techniques ingeneral . L in ing requlrements for tunnels varyimmensely depending upon the ground condi t ions.Tunnels in hard rock nay be conpletely unsupporEed

e r i t h no add l t i ona l ' cosmeE lc r l l n l ng . I n o the rt ypes o f s t r aBa , r ock bo l t l ng uay be su f f i c l en t t oprovide permanent scabl l i ty to Ehe excavat lon rr l - ththe posslb le use of nesh and sprayed concrete 10more f r iable zones to prevent f ragnents f romfa l l i ng o f f o r su r f ace weaEhe r l ng .

For weaker ground condl t lons, pernanent support naybe achleved using arches, beams and columns orcomp le te r i ngs , a l l f ab r l ca ted f r on s tanda rd 6 tee lsec t i ons . .A l t e rna t i ve l y sphe ro lda l g raph iEe , cas tst .eel segments or precast concrece segnenEs provldea convenienE form of c i rcular Eunnel construct ion,part lcular ly ln sofE ground condl t lons c lose - to theaurface. Cast steel segnenEs would noroal ly beenployed as the f ln lshed l in lng because of theirh lgh load carry lng capaci ty, but the othersteelwork support sysEer ls and the precast concretesegnents nay also be used as temporary works pr lorto l in ing ln concrete on a more pentranenE basis.Flgure 9 shows a typlcal sof t ground cunnelconstrucElon ln which precast concreCe uni ts wereinstal led as temporary support pr lor to l in ing wlrhln s lEu concrete. Flgure 10 ls a photograph takenlnside one of the tunnels.

As for lnsets, accuraCe deEernlnat ion of thelnposed loadlng ls of fundanental lnportance ln thedeslgn of tunnel l ln lngs. Hany soi l and rocknechanlcs theor les are aval lable Eo deterninepressures on tunnels ln var ious groundcond l t i ons

q . Two bas l c t ypes o f l oad ing

predoninate. One consists of a t r iangular shapedzone of roof st rata whlch is consldered Co breakaway under graviEy to Lnpose loading on thesupport lng structure. This could occur insE ra t l f Led rock o f a conpe ten t naEu re w i t h no s i deo r f l oo r l oad ing p resen t . The second p r l nc l p l e ,used in neaker ground, considers a y ie ld zone toexlst around the opening J. This occurs becauseEhe strengEh of the rock is lncapable ofwichsEandlng the high local lsed sBresses r , rh ich arecreated around the per lneter once the excavat ionhas Eaken p Iace . I n i t i a l y i e l d i ng f l : r s t r akes

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place at the excavatLon face and graduel ly spreadsfur ther lnto the grouod unt l l s tabl l l ty is onceagaln restored. The opening ls thereforeconpletely r lnged by a part ly crushed (y le ld) zone.

In both these approachee, the tLme since excavat ionand the dlstance f ron the excavat lon face arecr lc lcal . An unsupported roof , shlch is coopetencshen excavated, nay becone unstable wi th c ioe asdefornat lon takes place and larger gravi ty forcesare brought lnCo play ln conJunct lon wiCh theLncreased t r langular loadlng. Closure of an

excavat l -on, shlch ls restra l .ned at the dr lvageface, Lncreases t l th d istance back f ron the face upto approxlnately f lve to s ix d ianeters shen at chisposl t lon l t ls Eost ly conplete 3. Sone rocks,however, such as salr , exhlb i t t loe dependentmoveEents whlch nay contLnue throughout the tunnel1 1 f e .

Based on the prevlous commencs, lE can be seld thacthe ra r t ' o f t unne l l l ng cons i scs o f i ns ta l l l ng t hemost su{table (safe, econooLcal and serv iceable)l ln lng at exact ly the r lghc t loe ln phase wi th Ehe

F igu re 10 . The i ns i de o f t he Gra in Power ScaE lon coo l i ng wa te r i n t ake t unne l s .

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proceedlng excavat lon. The bul l .d up of load for atr langular rgof zone approach ls a progressive onedue to the gradual loosenLng of the rock ln theroo f dependen t upon t iDe . Res t r l c t i on o f r oo fde fo roa t l on by l nned la te l ns ta l l a t l on o f t he l i n i ngprevents the zone of inf luence f ron spreadlng andnLnlnizes gravl ty forces. In the caae of a y le ldzone, lmmedlate lnsta l lat lon of support c lose tothe dr lvage face could be achleved but lEs requlred6trength sould be excessive. InsEal lat lon of thel ln lng at some dlstance back f roo the face needsless support a6 part of the c losure has al readytaken p1ace. Provlded the ground renalns cotopetent(ee l f s t and lng ) , t hen t he re -adJus ted s t r esses w l11be carr ied by the 8l rata or wl th the asslstance ofnin lnal tenporary support pr lor to l in ing wl th ath ln skln of st ructural concrete.

The technlque of a l lowlng the rock l tsel f to carryae much of che poat excavat lon atress as posslb le,ln conJunct lon s l th a n in lnal l ln lng, nay becons ide red t o be ano the r r sec re t r o f good t unne ldeslgn. The Nev Auscr lan Tunnel Method (NATM) 5

deEonstrates th ls aspecB to the fu l l and enploysonly rock bol ts, nesh and a th ln skin of sprayedconcrete as Che pr luary support sysCeo whichasslsts the ground to carry the load.

Ic ls l r l th in th ls context that concrete ls used lntunnel construcClon. The ground condi t lons and i tsde fo rna t l on cha rac te r l s t i c s subsequen t Eo excava t l onnust be knorn before l in ing concepts can be fu l lyfornulated. Pre-knowledge of ground condlc ions lsobEalned f ron geological .and hydrogeologlcal boreholedata. The NATM goes even fur ther ln l ts lnpl lc l tre l lance on lnstrunentat ion and ln sLcu observat lonsas tunnel construct lon proceeds. These observat lonsare used not only to checkr 'on the perfornance andsa fecy o f t he t unne l bu t t o ' gu lde t he p rov l s i on o fseconda ry o r t e r t l a r y supPo r t .

Ic can be seen that . the possib le range of concreteusage for tunnel construct ion ls therefore wide andenbraces the fu l l range of sprayed, precast and insLtu work. The use of sprayed concrete isnldespread underground and nany references areava l l ab l e e l sewhe re conce rn lng iEs use .

2.7 Sp i ra l chu te bunker shaf ts

The concrete structures discussed so far have al1been related to verBlcal shafEs or hor izontaltunnel dr lvage. We now coDe to var lous structureswh l ch a re consCruc ted t o f u l f l l spec i f l c f unc t l onsconnected wl th working olne operat lons.

In a mlne, handl ing facl l l t ies underground are ofexEreme lmportance for t ransport lng the exlracted

nater la l - to the surface. Coal is nornal lyt ransporced underground f roB extract ion face to theho l sc l ng sha f t , o r a l t e rna t l ve l y t o t he su r f ace upan l nc l l ned d r l f t , us i ng conveyo rs . The cu r ren tt rend ln coal Elnes ln the Uni ted Kingdom,

fol lowing thelr or ig inal developrnent ln Gernany, L6to use splra l chute bunker shaf ts (see Flgure 11)lo l ine on the conveyor sysEen. These provldestorage facl l l t ies underground ln addl t lon to belnga means of regulat ing coal f lov. Coal is fed lntothe in let chute, s l tuated ln che bunker topchauber, and f lows downwards splra1ly ln the chutese t i n t o t he va l1 . The pu rpose o f t he sp l r a l , asopposed t o a f r ee f a l 1 sys ten , l s t o con t ro l t heinf low of coal so that degradaclon and the r iak oflncendive sparklng are reduced and wear on theshaft r ra l ls and dust are miniu ized. Rernoval of coalis through Ehe conical out let in the bot tdu chanberroof , feedlng back onto the naln 1 lne conveyortransportat lon systen. The bunker shaf t shown lnF lgu re 1 l l s cons t rucEed f r om re l n fo r ced conc re te ,c a s t i n s i t u .

At the present t lne, splra l chute bunker shaf ts arecons t ruc red w l t h a d l ane te r o f 7 . 315 n ( 24 fC ) andnlEh a helght nornal ly of about 40 o Eo glve acapacl ty shen fu l l of 1000 tonnes.

Construct lon of spira l chute bunker shaf ts can Eakeseveral forns. They nay be instal led uslng snal lp recas t conc re te b l ocks (Thyssen sys teo ) o r l a rge r ,bo lEed , p recas t conc re te sha f t l i n l ng segnen ts(Cenentat lon l , t ln lng/Buchan systetr) . In both cases,spec ia l un i t . s a re r equ l r ed f o r t he sp l r a l ( seeF igu re 12 ) . Vo id f i l l i ng beh lnd t hese un l t s du r l nglns ta l l a t l on i s ca r r i ed ou t us l ng a g rou t l ngp rocess . A l t e rna t l ve l y , i n s l t u conc re te can beused w i t h o r w l t hou t g l ass f l . b re r e l n fo r cedconcrete panels as permanen! fornwork. In a l lt hese f o ros o f cons t ruc t i on , cas t basa l t t 1 l esp rov lde t he wea r i ng su r f ace f o r t he sp l r a l p ro f l l e( s e e F l g u r e 1 l ) .

Des lgn p r l nc i p l es f o r t he i n f eed chu te t o t hebunke r t op , t he sp i r a l l t se l f and t he ou t f eedsys ten , a re ou t l l ned by voss 5 , I n t he s t r uc tu ra ldes lgn o f t he sha f t , t he ques t i on o f l oad ing i sf o renos t : two k i nds requ i r e sc ru t l ny . F l r s t , t hecon ta i ned ma te r i a l imposes s i l o - t ype , l a t e ra lp ressu res and ve r t i ca l shea r f o r ces on Che wa l l .Second , t he poss ib l l l t y o f ex te rna l g round l oad ingmus t be cons ide red . Howeve r , i n nos t cases ,bunker shaf ts are s i tuated ln cotrpeEent ground andw l l l on l y be sub jecced t o ex te rna l g round p ressu rest f f u r t he r ad jacen t deve lopmen t d r i vage i s ca r r l edou t subsequen t l y . I f t h i s occu rs , g round novenen tscou ld be l a rge , v i r t ua l l y i nposs ib l e t o de f l neaccu raee l y and canno t be accomuoda ted l n des lgn .

F lgu re 12 . Ceu ren taE ion M in i ng /Buchan bo l t ed , p recas t conc re te , sp l r a l chu te bunke r sha fE segnenE .

L 4

I n conpe ten t g round , t he l oad o f Che coa l con ta l nedln t he bunke r can be t r ans fe r red d i r ec t l y f r om thel i n i ng t o t he su r round ing g round by mechan i ca li n t e r l ock . La te ra l p ressu res a re r es i s t ed d i r ec t l yby t he rock , and ve r t l ca l shea r f o r ces byfr lc t lonal reslstance and nechanical inter lock.Lia lngs of bol ted precast concrete segments, lns l tu concrete or f lbre re inforced concrete panelt l ipes therefore need only be designed nonlnal lyfor st rength as the internal loadl-ng is d lss lpated

dlrect ly into the ground. Thls leaves the baee s laband bot ton chanber structure to carry the ef fect lveve r t l ca l s i l o p ressu re aC t ha t l eve l . The sp i r a lchuce also servea to lmprove the interact ion betweenthe bunker and the ground, provid lng an exEernalco rksc rew e f f ec ! . I n f he case o f t he b l ock l i n i nghowever, in whlch Che elenenEs are noc physlcal tyconnected together, considerat lon may need to be glvento carry lng Ehe fu11 welght of the 6haf t l in ing andEhe bunker contentE on the bot ton charnber structure.

sEcTtott c-c

Floor r lob pruturt rr l i r fond groul ing pip. l

s E c T r 0 N 8 - 8

F igu re 13 . sunp Eank f o r ho ld l ng m ine wa te r p r i o r t o pump ing Eo su r f ace .

l -5

stroro c c$cr :o gror iag cl i l rctr

l lt l

V I E W O N B - B

F lgu re 14 , Unde rg round sa fe t y p l ug and bu l khead doo r .

2.8 Sump tanks

The con t ro l o f ea te r l s an lmpo rEan t aspec t o foperat lng an underground nine. Sunp tanks arel nva r l ab l y r equ i r ed Eo ac t as co l l ec t l ng po in t s f o rwater. Punplng arrangenents can then be eoployedfo r iEs t r ans fe r t o o the r pa r t s o f l he D lne o r t ot he su r f ace f o r d i sposa l .

A typical re inforced concrete sump tank isi l l u s t r a red l n F l gu re 13 . Th i s Eank has beens l t ua ted i n an a rea whe re i ng ress o f wace r cou ldoccu r t h rough t he s t r a ta beh lnd t he s i de wa l l s andbe low t he f l oo r . Hence , a p ressu re re l l ev i ngsys ten has been l ns ta l l ed . The p ressu re re l l ev l ngsys ten consLs t s o f a number o f p l pes l ead ing ou tf rorn below the f loor s lab to prevent bul ld up ofsE ra ta wa te r p ressu re wh i ch cou ld danage t hes t rucEu re . These p l pes cou ld a l so be used Eo g rou tup t he i nEe r face zones f o r sea l l ng pu rposes l f l twe re necessa ry t o f l l l t he who le a rea conp leEe l yn l t h conc re te due ro excess wa te r i ng ress .

I n some a reas unde rg round , t he sE ra ta cond l t i onsnay be suf f lc lent ly conpetent and lnperrneable Eoa l1ow wa te r s t o rage w i t hou t any add l t l ona ll i n i ng . A t h i n l aye r o f sp rayed conc re te on s tee lnesh may su f f l ce l n oEhe r a reas . Howeve r , whe re ano re subs tan t i a l sE ruc tu re l s r equ l r ed , t he des ignshou ld f o l l ow t he gu lde l l nes o f Lhe re l evan t Codeo f P r a c t l c e / .

2 . 9 P l u g s

Al l led to the cootro l of eraEer in a mlne is theab l l i t y ! o sea l o f f secE ions aga ins t naJo rl ng ress . P lugs may be l nc l uded f o r sa fe t y , as m inedeve lop rnen t p roceeds , o r t hey oay be l ns ta l l ed asan emergency p rocedu re i f a l a rge l n rush occu rs .The foro of the plug var ies depending upon thecond l t l ons . I n an ene rgency , a so l l d conc re te p l ugwould be constructed as a permanent seal ing of ftDeaau re . P lugs l ns ta l l ed du r l ng an Ln l t l a l n i nedevelopnent scheme wi l l need to a11ow men,

r6

nater la ls, equlpoent and serv lces to pass throughand a l so be capab le o f r ap id c l os l ng o f f . Such aplug, lncorporat lng a bulkhead door, ls shown lnF lgu re 14 .

The p l ug wh i ch i s i l l u s t r a ted has been des igned onthe bas i s t ha t f u l l hyd ros ta t i c p ressu re cou ldprevaLl ln the event of a f lood, the naxinun headbelng the depth f ron Ehe ground surface to thelnsEa l l a t l on l eve l unde rg round . Th ree na lne lemen ts a re i nco rpo ra ted i n t he p l ug :

(a ) conc reEe cy l l nd r i ca l p l ug ;(b ) s t ee l l oad t r ans fe r cy l i nde r ;( c ) s t ee l bu l khead doo r .

The concrete cyl lndr lcal p lug has two purposes. T ' t lef l r s t i s t o p rov l de a ba r r l e r t o w l t hs tand t he endhyd ros ta t i c p ressu re . Th i s l s ach leved byp rov ld i ng a su f f i c i en t l eng th t o keep t he shea r a tthe concrete to rock lnter face wi th ln pernlssib lel l n l t s . Second l y , t he p l ug i s des lgned as a oeansof prevent lng the passage of nater through the plugl t se l f , aE t he conc re te t o r ock l n t e r f ace and a l soch rough t he sE ra ta . When g rou t l ng t he con tac t zonebetween Ehe plug and the rock, or grout ing the6 t ra ta , g rea te r p ressu re t han t he p reva i l i ng headl s r equ l r ed , t o chase t he wa te r back a l ong i t slnf low paths. The concrete tube nust therefore becapab le o f w l t hs tand ing p ressu res marg lna l l y l nexcess o f hyd ros ta ! i c i n t he rad la l d i r ecE ion .Add lC lona l g rou t sea le he lp t o c l ose o f f poss ib l el eakage pa ths .

The steel load t ransfer cy l lnder bears onto r lngf langes and al lons che bulkhead door pressure Eo beca r r l ed by t he conc re te cy l l nd r l ca l p l ug . Enoughf l enges a re p rov i ded t o r educe t he bea r i ng s t r essesto pe rn l ss l b l e l l o l t s . The s tee l bu l khead doo r i sdes lgned t o ca r r y t he f u l l hyd ros ta t i c p ressu re aoda l so l nco rpo ra tes a man access t ube . Se rv l ces canbe ca r rLed t h rough s tee l p i pes e rnbedded i n t heconc re te cy l l nd r l ca l p l ug , g l ands be lng l ns ta l l eda t bo th ends o f t he p l pes f o r sa te r sea l i ng .

5. Gonstrrrction Method.s3 . 1 I n t r o d u c t i o n

The use of concrete ln underground developrnent workhas t h ree d l s t l nc t aspec t s . F l r sE , any excava t l onnus t be secu red be fo re casE lng t he conc re te aga ins tl t . Th i s l nvo l ves p rov l d i ng t he co r rec t t enpo ra ryuorks support ln phaee wl th the excavat lonprocedure. Second, fornwork and fa lsework arerequLred, to ensure thaL the concrete, when placed,remains ln the desired posi t lon and ls of the shapeexpected. The th l rd aspect of concreteconstruct ion ls the abl l l ty to roove the fornworkand fa lsework safely and quickly for subsequentpou rs .

I n Ehe f o l l ow ing secE lon6 , t hese aspec t s a reconsLde red w i t h r e fe rence t o t he pa r t l cu l a rs t r uc l u res p rev l ous l y desc r l bed . Subsequen tsecELons cover batchlng planc and t ransportat lonand p l ac i ng t echn lques .

3.2 Co l la rs and fo reshaf ts

Figure 15 i l lustrates lhe method employed tocons t ruc t t he co l l a r and f o resha fE o f a f r ozensha f t and F lgu re 16 l s a v l ew l ook ing i ns l de a t t heteopo ra ry suppo r t p rov l ded f o r such a sc ruc tu re ,p r l o r t o l i n i ng l n conc re te . Th t enpo ra ry suppo r t

f o r t he excava t l on cons i s t s o f s t ee l l l ne r p l a tes

and s tee l r l ngs , t he l a t t e r be ing f ab r l ca ted f r ons tanda rd sec t i ons . Th l s l ype o f t eEpo ra ry suppo r twould normal ly be used through the sof t , sur faceso i l depos l t s un t l l bed rock i s r eached . On f u r rhe rs lnklng ln competent ground, only rock bol ts andmesh need to be used for tenporary support .

I n f r ozen g round , t he s t r engEh o f t he so f t su r f aceso l l depos i t s Ls enhanced t o such an ex tenc t ha t l trenalns competen! when excavated. The 1lner p lafesand r i ngs a re p rov i ded , t he re fo re , as an add l t i ona lsafety neasure and also to prevent squeeze on thef resh l y cas t conc re te l l n l ng as a r esu l t o f t hdw lngln t he g round caused by hea t o f hyd ra t l ondevelopnent. However, care nust be Eaken to ensuretha t t he i ce wa1 l i s conp le te l y c l osed a round i t spe r i ne te r , be l ow t he f r eeze ce l l a r , i n o rde r Eoprevent Lngress of ground water Lnto theexcava t l on .

Where the ground f reezlng nethod i .s noE used,conslderat lon oust be given to provid ing teuporarysupporE which can sustain the inposed groundp ressu res . A dewa te r i ng scheme cou ld a l so beneeded .

The l ln lng forowork and oeans of handl ing theconc re te i n t he co l l a r and f o resha f t a re s i n i l a r t ot he equ i va len t i t ens l n s t anda rd sha fE s l nk l ngp rac t l ce . They a re de ta i l ed l a t e r i n Sec t i on 3 .4 .

T l p D l n g

F o p o

8 r n k t r n a n a

V . n t l l . t l o n C r b i n

F r n

A c c a r l

L a d a t a r i a y

H o p p i t

T o n p o r r r y S u p p o r t

l l n e l

T a m p o r a r y S r t t o r t

P l r t . !

T r r c l l o u n t a d

! . c k h o .

T Y P I C A L F O R E S H A F T

c o x s T R U c T t o x

F igu re 15 . Co l - l a r and f o resha fE excava t i on and t enpo ra ry suppo r t .

L 7

F igu re 16 . W is tow No . 2 ( upcas t ) sha f t co l l a r and

3 . 3 A i r a n d f a n d r i f t s

Provld ing a tenporary works schene for a i r and fand r l f t s has i t s own pa r t l cu l a r p rob lens . AsDen t l oned l n Sec t i on 2 .4 , connec t l on t o t he sha f t

Eakes place at the most vulnerable polnt for groundstabl l l ty and ground nater ingress lnto theexcavaElon. At th is point , the tenporary worksscheme for the shaf t construcl lon must be Eatchedup l r i t h t ha t f o r t he d r l f t . I n add i t i on , i n f r ozenground, the f reeze cel lar muat be supported aboveth i s pos l t l on r h i l e excava t i on p roceeds be lov ( seeF l g u r e I 7 ) .

In conjunct lon s l th a f tozen shaf t , a f rozen groundtenporary works support systen for the dr l f t can bep rov lded . Howeve r , t h l s i s suscep t l b l e t o seve reground novements ln the forru of heave dur lngfreezlng and seEt lenent ln the thasing per lod.Provided the ground condl t ions are sul table, theau lho r r s p re fe r red DeEhod o f t enpo ra ry wo rks Ls t hefo l l ov i ng .

( l ) P rov i de scee l shee t p l l es f o r t he d r l f t r i gh tthrough to the proposed shaf t col lar excavat ionpe r i ne te r , p r i o r t o l ns ta l l i ng t he sha f t f r eezetube d r i l 1 pad and t he f r eeze ce l l a r .

( 2 ) Du r l ng t he f r eeze ce l l a r cons t ruc t i on t excava tebe low t he f l oo r s l ab t o p rov l de re i n fo r cedconc re te co rbe l s wh l ch cou ld I a te r become anin teg ra l pa r t o f t he sha f t , r e i n fo r ced conc re teco l l a r s t r ucEu re . Ca re shou ld be t aken no t t oexcava te deepe r chan t he t op l eve l o f t he p roposedd r l f t r oo f s l ab . P rov i de enough co rbe l s ! o ca r r yt he we igh t o f t he secE lon o f f r eeze ce l l a rspann lng ac ross t he d r i f t . P rov i de re l n fo r cemen ta t t he rea r o f Che co rbe l f o r bend ing ou twa rds ,on exposu re du r l ng t he sha f t excava t l on , t o p rov l dethe necessa ry t l e l n w l t h t he sha f t co l l a r . Thef reeze ce l l a r s t r uccu re l t se l f , shou ld be are l n fo r ced conc re te s t r ucEu re capab le o f be lngca r r i ed by t he co rbe l s ove r t he w idEh o f t hed r i f t excava t l on .

l 8

f o resha f c unde r cons t ruc t i on .

P rov id i ng shee t p l l es r l gh t t h rough t o che sha f twa l l ensu res t ha t t he g round 1s co rop l - e te l y secu reda t Eh i s pos i r i on , wh i l e t he f r eeze ce l . l a r l ssuppo r ted f r om the co l l a r s t r uc tu re . Whe re g roundwa te r l s p resen t , a we l l dewa te r i ng sys l em oay berequ i r ed .

I n Sec t i on 2 ,4 , IE was reconmended t ha t connec t l ono f t he d r l f t t o t he sha f t shou ld no t occu r , i n t hecase o f a f r ozen sha f t , un t l l t haw lng se tE lenen t l sconp le te . P rov i s l on nus t be oade , t he re fo re ,du r i ng cons t ruc t l on f o r t h l s t o be accommoda ted .G a p s , w l E h o r n l t h o u t c o n t l n u i t y o f r e l n f o r c e r u e n t ,ous t be a l l owed i n t he f l oo r , wa l l s and roo f f o rt h i s pu rpose . Whe re t he re i n fo r cenen t i s n i n lma l ,a 300 nu r gap w i t h con t i nu i t y wou ld p robab l ysuf f lce. For an abundance of re lnforceuent ln thedeep bean s ide wal ls of the box cross-sect lon dr l f t(see Sect lon C-C tn Figure 6) , rehich provldes anuch stLf fer e leoent of realstance to bendlng, awlder gap preferably of at least a required lapl eng th , shou ld be a l l owed w i t h d l scon l l nu l t y o f t hesteel . The detai l r [ust a lso be watert ight andrequlres a steel seal lng plaEe across the back ofthe gap. Fron Ehe posl t ioning poln! of vLes, thebest locat lon is away f ron the shaf t towarde checen t re p l l e cap .

Propr ietary formwork systens can be eoployed fort he cons t ruc t l on o f a l r and f an d r l f t , s w l t h t r eg t l esfo r r oo f so f f l t suppo r t . Conc reE ing p roce< lu res a res i n l l a r t o t hose used i n su r f ace wo rks .

3 . 4 S h a f t l l n l n g

F lgu re 17 l l l u s t r a tes t he bas i c e l enen t s l nvo l vedln t he l i n i ng o f sha f t s . L i n i ng 16 ca r r i ed ou tdownwards, as s inkLng proceeds. The face of theexcavatLon ls only advanced as far ahead of thel ln lng as the ground condlElons al low, the s ldesbelng secured by rock bol ts and nesh. In wetcondl t lons backsheet.s of PVC, fastened to the rockbo l t s and oesh f o r cas t l ng t he conc reEe aga lns t ,are used to channel the wacer behind, out f low belng

Sink ingheodf rome

Muckingsystem

Brine rnqinFree ze ce l tor

4 Orumcopston winch

Vent i lo t ionDouble drum

w i nderAirond

dr i f tshqft cot lqr

Freeze tubes

Scrv i ce s

Honging rodsfor formwork

Pumpingryr t rm

Mutt i -deck scof fotd

Muc k inguni t

Stondqrd formwork

Muck hoppi t Cqctus grob

Figure 17. Coumencement of shaf t s inklng and l ln lng.

t 9

V c n t i l a t i o n

R i r i n g M r i n

B l a t t i n g B o r

C o n c r r t c

D i r t r i b u t i o n

D e r h P o l

P r o t r c t i v r

C a n o p y

S t c a d y C h e i n r

G u i d c R o l l r r r

S h u t t r r i n g S h u t t r r i n gW i n c h r t

S w i t c h g r r r &

L i g h t i n g

T r r n s f o r r n r r r

S i g n i I C a b l c

H r n g i n g R o d r

C o m m u n i c e t i o n

C r b l r

C o n c r c t i n g

Pipr Boo t - \ - -

W r t o r T a n k

T o o I 8 o r

S t e g c L i g h t i n g

S t r g r W e t e r

P u m p

S t c a d y

J a c k sV c n l i l a t i o n

O p c n i n g C o v c r

S i n k i n g L i g h t r T o o l B o x

D r i v c r c C a b R o t a r y A r m

M u c k i n g

U n i tC a c t u g G r a b

H o p p i t s

S u m p

P u m p

F i g u r e 1 8 .

20

Sca f f o l d used f o r sha f t s l nk i ng and l l n i ng .

conc ro l l ed v l a p i pes t o t he g rou t po r t s l n t hefornwork for punping to the surface dlsposalp o l n t s .

A11 s lnking, l ln lng and fornwork handl lngope ra t l ons l n a sha f t a re ca r r i ed ou t f r om a nu l t l -deck sca f f o l d suspended f r on t he head f rane ( seeF tgu re 17 ) . A caps t . an w inch ra l ses and l owe rg Eheecaffo ld. Flgure 18 shows the general arrangeoento f a t yp l ca l s ca f f o l d and F lgu re 19 l s a v i ew o f afou r deck sca f f o l d be lng i ns ta l l ed l n a sha f t . .

Sha f t l i n l ng f o rmso rk ( see F lgu re 20 ) i s suppo r ted ,dur ing concrete pour ing, by rneans of hanglng rodssuspended f ron the l l f t above. The kerb r ing, oncei t l s l l ned and l eve l l ed , ac t s as a scop -end co t heboE ton o f t he l l f t be l ng consEruc ted and p rov l dea a

seat lng upon whlch to lo i rer the complete eet offormwork r lngs f ron the prevloue pour. Thelower lng of the forosork ls achLeved by rneana ofw lnches s l i ua ted on l he sca f f o l d ( see F lgu re 18 ) .

F l gu re 2 l i l l u s t r a te6 t he conc re te l l n l ngsequence. Pour doors in the fonnwork asslst lJ l ththe placlng of the concrete and the specla l shaped

Jo ln t ( see F igu re 20 ) pe rn lEs na t ch lng up t o t heprevlous pour. The concrete 1s t ran6ported f ronthe su r f ace , v i a a ve r t l ca l p l pe l l ne l n t he eha f t ,and l s r ece i ved f i r s t by a dash po t and t hen by ad l s t r l bu t l on box ( see F tgu re 21 ) . Passage i n t o t he

fornwork ls by oeans of f lex ib le hoses at tached toe tee l p tpe ou t l e t s f r om the d l s t r l bu t i on box .} { e thods o f conc re te d i s t r i bu t l on a re d l scussed no ref u l 1 y l a t e r l n S e c t l o n 3 . 1 0 .

F i g u r e 1 9 . W l s E o w N o . 2 ( u p c a s E ) s h a f t f o u r - d e c k s i n k i n g s c a f f o l d b e i n g i n s t a l l e d .

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