C hc .1 NGUYN S NGC C HC DNG CHO SINH VIN NGNH XY DNG CNG TRNH . NH XUT BN GIAO THNG VN TI H NI - 2005 2.C hc Chu trch nhim xut bn L T GIANG Bin tp THN NGC ANH Ch bn v sa bi XNG IN TRNG I HC GTVT NH XUT BN GIAO THNG VN TI 80B Trn Hng o H Ni T: 9423345 Fax: 8224784 05 230/805 GTVT075(6V)MS In 620 cun, kh 19x27cm ti Xng in Trng i hc GTVT. In xong v np lu chiu qu III nm 2005. Giy chp nhn k hoch xut bn s 230/XB QLXB ngy 03/03/2005 LI NI U C hc .3 Chclmtmnhctrongchngtrnhotoksxydngcng trnhgiaothngcaTrngihcGiaothngvnti,nhmcungcpchosinh vinnhngkinthccbnnhtvcctnhchttrngthicavkhi nguyn trng; cc qu trnh v hin tng c hc xy ra khi xy dng cc cng trnh trnvtrong,ttmraccphngphpphhuchiuqu,cchiu khinhplplc,lmnnhcccngtrnhxydngtrn,trongv bng . Vithigiangingdycamnhcl60tit,cunschnhnykhngth trnhbyhtcymikhacnhcachclthuytvngdng,m mi ch nu c mt cch tm tt mt s vn rt c bn ca c hc . Do trnh bn thn c hn m kin thc c hc li rng, nn chc chn s khng trnh khi nhng thiu st trong khi vit. Ngi vit rt mong c s ch bo ca bn c gn xa. NhngkinnggpxingivBmnakthutKhoaCngtrnhTrng i hc Giao thng Vn ti H Ni. Chng ti xin trn trng cm n. H ni ngy 30 12 2004 Ngi vit PGS.TS. Nguyn S Ngc Ch nhim B mn a k thut, Th k Hi C hc Vit Nam 4.C hc MC LC Li ni u3 M u7 Chng I V TNH CHT C BN CA 16 1.1.Cc khi nim c bn v - 1.1.1. S thnh to cc loi - 1.1.2. Thnh phn ca 17 C hc .5 1.1.3. Kin trc ca 25 1.1.4. Cu to ca 26 1.1.5- Tnh khng ng nht v d hng ca 27 1.1.6. Mt s loi thng gp28 1.2.Cc tnh cht c bn ca 35 1.2.1. Mt s ch tiu c trng cho hm lng cc pha trong 37 1.2.2. Tnh cht c hc54 Chng II CC TNH CHT CA KHI NGUYN TRNG127 2.1.Khi nguyn trng v mt vi c im ca n.- 2.1.1. Khi nim v khi nguyn trng - 2.1.2. Vi c im ca khi nguyn trng128 2.2.Cc tnh cht ca khi nguyn trng132 2.2.1. Tnh phong ho133 2.2.2. Tnh cht nt n143 2.2.3. Tnh cht c hc157 2.2.4. Nc v khi nguyn trng187 2.2.5. Mt s tnh cht khc ca khi 196 Chng III KHO ST V NH GI KHI 202 3.1.Kho st khi - 3.1.1. Mc ch v ni dung kho st khi - 3.1.2. Nguyn tc c bn trong kho st khi 203 3.1.3. Cc phng php kho st206 3.2.Phn loi khi 213 3.2.1. Phn loi theo cc ch tiu c lp214 3.2.2. Phn loi theo cc ch tiu tng hp- 3.3.nh gi khi 225 3.3.1. nh gi tnh cht bin dng ca khi - 3.3.2. nh gi bn khi . 227 Chng IV N NH NN V B DC 228 4.1.S n nh ca nn - 4.1.1. Khi nim- 4.1.2. Sc chu ti ca nn 238 4.2.n nh b dc 245 6.C hc 4.2.1. B dc v n nh ca n- 4.2.2. Tnh ton n nh b dc256 4.2.3. phng v chng trt b dc276 Chng V TRNG THI NG SUT V P LC XUNG QUANHCNG TRNH NGM284 5.1.ng sut t nhin trong khi - 5.1.1. Cc gi thuyt v s phn b ng sut trong 285 5.1.2. Trng thi ng sut ban u ca khi 287 5.1.3. S phn b li ng sut trong v tri t291 5.1.4. Cc phng php o ng sut t nhin trong khi 294 5.2.Trng thi ng sut v bin dng ca xung quanhcng trnh ngm305 5.2.1. Khi nim v cc cng trnh ngm- 5.2.2. Trng thi ng sut ca xung quanh cng trnh ngm310 5.2.3. Bin dng ca xung quanh cng trnh ngm324 5.3.p lc trong cng trnh ngm328 5.3.1. Khi nim v p lc - 5.3.2. p lc trong cc hm ngang333 5.3.3. p lc trong thnh ging v hm nghing355 Ph lc365 Ti liu tham kho372 M U1.V TR V I TNG NGHIN CU CA C HC Hngnghnnmqua,ng vai tr rt quan trng trong cc hot ng cthccaconngi.Nhngcngc laongvvkhthscangi nguynthu,nhngKimtthps ngsngsngcnhtngconSphinx khng l bng bn dng sng Nil Ai Cptthinl,nhngnginhcao chctri;nhngnghmt,hm ngstxuynquanihayngmdi ybinnilinccoxaxi;nhng Hnh 01 Kim t thp v Sphinx vng Giza gn Cairo (Ai Cp) khong 2700 2550 TCN C hc .7 cng trnh bng ni ting hay nhng khi tng khng l tc ngay trn vch ca th gii ngy nay u do hay nh to nn. ngy cng tr nn gn gi trong i sngcon ngi. Vvyvicnghincutnhchtvtrngthica-nhtlcakhi nguyn trng di tc dngca ngoi lcnh thin nhin (trng lc, cc tc dng a cht) hay nhn to (lc do cc cng trnh xy dng, do hot ng sn xut ) l rt quan trng v cn thit. p ng nhu cu nghin cu trn, mt mn khoa hc mi c ra i, gi l C hc . C hc l mt mn khoa hc lin quan ti nnglng,lcvtcngcachng lnvtth,nncthcoichcl mtbphncangnhkhoahcchc acht,chuynnghincutnhcht, trng thi ca v khi nguyn trng, cc qu trnh v hin tng c hc xy ra khi tin hnh thi cng cc cng trnh trn , tm ra cc phng php ph hu c hiu qu, cch iu khin hp l p lc v lm n nh cc b dc , nn . Mnkhoahcchcmangtnhcht ngdng.Cclnhvcnghincucanc litrctip,thitthcnccngnhkinht qucdn,nhtlccngnhm,giaothng, thuliNhnghiubitvvccc trng, trng thi ca n s gip cho vic thit k v thi cng cc cng trnh trong v trn c hp l, c hiu qu kinh t v an ton hn. U ban C hc ca Vin hn lm khoa hc quc gia M (1966) nh ngha: C hc lmnkhoahclthuytvngdngv nhng ng x c hc ca , n l ngnh c hc lin quan n s phn ng ca vi cc trng lc bao quanh chng. Hnh 02 Nh m thnh ph Petra (Jorani ngy nay) o vo trong khi (th k VI TCN) Hnh 03 Nh th c B Paris (1163 1250) 8.C hc Hnh 04 Khi tng 4 Tng thng M ni Rushmore (bang Nam Dakota M) (1927 1941) C hc da trn cc thnh tu ca vt l cht rn, cc l thuyt do, thm, lubin,cchiubitvacht,ahovccmnkhoahckhc.Ncng c coi l phn nn tng ca khoa hc v tri t- nht l khoa hc m. Khc vi cc vt liu khc, rt a dng, t ng nht nn i khi kh hiu v khdon.Mtkhc,ccschcvhnhhccaccbitonchc thng khc vi cc s c in ca cc bi ton n hi, do nn vic nghin cu cng c nhiu im ring bit. Khithicngcccngtrnhtrn,ccqutrnhchcchnhcnghin cu trong c hc l s hnh thnh trng thi ng sut ca khi v s thay i can,schuynngcaccdngkhcnhau,stngtcgiavv chng Vic nghin cu C hc gm mt s hng sau: - Tnh cht ca v khi nguyn trng -L thuyt ph hu -S xut hin v cch iu khin p lc khi thi cng cng trnh ngm -S chuyn ng ca khi thi cng cng trnh -n nh cc b dc -Cc hin tng ng lc trong khi -Qu trnh thm trong -S tng tc gia cc hin tng kin to khu vc v vi a cht cng trnh trong khi 2.S LC LCH S PHT TRIN C HC C hc l mt ngnh khoa hc rt tr. Lch s pht trin ca n c th chia thnh ba giai on: Trong giai on u, khi ngi ta bit khai thc v cc khong sn su trong lng t th vn n nh hm l c t ra. Vic la chn cc phng php chng l i hi phi nghin cu cc qu trnh bin dng v ph hu ca xung quanh hm l, cc quy lut pht trin ca cc qu trnh y trong khng gian v thi gian. Tuy vy, giai on ny, vic nghin cu mi ch mc m t, tng ktcchintng,chchaphntchcmtcchsusccchphtsinhv pht trin ca chng. Trong nhng nm 30 ca th k XIX, ngi ta quan st thy hin tng st ln mt t do vic khai thc than nm gn mt t ngoi thnh ph Lige (B) v mychcnmsau,hintngtngtcngxyramtvithnhphcac. Nhiu tc gi nghin cu chng v ra c nhng nguyn tc u tin, xc nhphmvinhhngcavickhaithchmlivimtt:Nm1864, J.Goodwin, mt k s ngi Anh nu kh y nhng yu t nh hng ti s st ln mt t nh h thng hm l, tnh cht ca , gc nghing v chiu di va, chiu su khai thc ngha l nhng yu t c nh hng quyt nh nht. C hc .9 Cng trong giai on ny, vic nghin cu cc thnh phn ng sut ca khi cngbtucch:nm1874,F.Rziha,mtchuyngiavhmcacv bnnmsau,giosngiThysA.Heimnulngithuytvthnhphn ng sut nm ngang trong khi v quan h ca n vi thnh phn ng sut thng ng, nhng khi , nhng gi thuyt ny cha c tha nhn v ph bin rng ri. nghin cu, th nghim , ngi ta dng cc thit b n gin hay hon thinccmyko,nn,unvccukpmukhikodonhvtlHlan P.Musschenbrock ch to t nm 1729. Ni chung, vic nghincu c hc giai on nymi chchn cc hin tng bn ngoi,ccgi thuyt thng mang tnhcht thc nghim, cha bao hm cc ch tiu phn nh thc cht khi b bin dng. Giai on hai c th tnh t cui th k XIX. Trong giai on ny, ngi ta xy dng c nhiu gi thuyt kh cht ch vbnchtvtl,cchccqutrnhxyratrongkhikhithicngcccng trnh. Nm 1885, M.Fayol, mt k s ngi Php v 4 nm sau, k s trc a ngi cW.Trompeternuralthuytvsphnvngplcxungquanhcng trnh ngm. Nm1907,giosngiNgaM.M.Protodjakonovragithuythnh thnh vm p lc trong cc cng trnh ngm. Cng trnh ny l mt bc tin rt ln trongchc,toiukintnhtonccthngschovchng,nhngcng cha ph hp vi cc cng trnhc tit din ln v nm su trong lng t. ng thi vi vic xut hin cc gi thuyt v p lc v trng thi ng sut xung quanh cng trnh ngm, cc dng c o ng sut v bin dng ca c ch to tinh vi, chnh xc cao hn v c th o trc tip ngay ti khi . Ngi ta cng bt u dng phng php m hnh nghin cu cc qu trnh bin dng ca xung quanh cng trnh ngm. Nm 1909, ngi ta dng phng php phun va lm n nh cc ng hm. Nm1912,T.Karmannghincutrngthingsutthtch-mt trng thi rt ph hp vi iu kin t nhin. Nm 1918, ngi ta bt u s dng neo lm n nh cc khi . Nm 1926, J. Schmidt a ra nhng gi thuyt v tnh cht n hi, kt hp vi l thuyt ca A. Heim v ng sut ban u ca khi , to nn nhng c s u tin ca C hc . Nm1938,nhachtngiChinR.Fennercngbnhngktqu nghin cu v p lc , ni chung cng gn vi kt qu ca J. Schmidt. Cng trong nmny,vinsXvitA.N.inniknurcimphnbngsuttrong khi c tnh n h s p lc ngang. Nhng nm sau, nhiu tc gi pht trin thm cng trnh ca ng. 10.C hc Nichung,tronggiaionny,ngitanghincusuvccqutrnh bin dng v ph hu ca trn mt t cng nh trong cc cng trnh ngm bng cc my o c chnh xc cao. Ngi ta gn cc qu trnh bin dng v ph hu do vic thi cng cc cng trnh vi cc qu trnh thay i trng thi ng sut ca khi . Ni mt cch khc, trong giai on ny, ngi ta chuyn dn dn t vic nghincucc hin tng bn ngoi sang vicnghincucc nguynnhngyra chng. Giaionthba-giaionchchinicthbtutnhtcui nhng nm 30 ca th k XX. Dotchlucnhiukinhnghimthctkhikhaithckhongsnhaythi cngcngtrnhngm,ngitanhnthynhngskhngphhpgiacc phng php tnh a ra v cc s tnh ton v chng. i vi , l thuyt v cc phng php nghin cu c hc mi trng ri rc l c s ca nhng gi thuyt cagiaiontrckhngcnphhpna,ngitabtusdngrngril thuyt v cc phng php nghin cu c hc mi trng lin tc, nht l l thuyt nhi,tmhiusthayitrngthingsuttnhindovicthicngcc cngtrnhtrongvtrngthicakhixungquanhcngtrnhkhicsthay i ng sut y. ngthivivicphttrinlthuyt,nhiuphngphpthcnghim nh gi trng thi ng sut ca khi cng c ra. Ngi ta s dng rt rng ri phng php quang n hi dng cho cc m hnh c th th hin c cc iu kin a cht khc nhau nh phn lp, khng ng nht Cc phng php a vt l dng nh gi trng thi ng sut ca m khng cn phi o bin dng ca n nh cc sng n hi cng c p dng ti thc a trn cc khi . Do thc t i hi phi xy dng c cc m hnh ging vi cc quy lut bin dng thc ca , nn trong giai on ny, ngi ta lp c cc s tnh ton bin dng khng ch cho vt th n hi m cn cho cc vt th bin dng theo thi gian. Nm 1950, ln u tin, phng php o hm mi kiu o (NATM) c nu ra. Nhngnm1950-1954,hainhnghincuXvitF.A.Belaenkov K.V.Ruppeneytlpccngthctnhtonplcxungquanhhmmc tnh n bin dng n hi- do. Trongkhong1955-1958,ccnhnghincuBalanJ.LitwiniszynvA. Salustowicz cng lp c m hnh tnh ton cho cc bin dng n hi nht. Nm 1957, k s ngi Php J. Talobre xut bn cun C hc trong trnh by tng i h thng cc vn v c hc v ng dng ca n trong xy dng cng trnh. Tnm1960,ngitabtunghincuvsbindngcatheothi gian.LinX,vnnycZh.X.Erzhanov,V.T.Glusko nghin cu rt su. Tronggiaionny,ngitahonthinccphngphpvdngco bin dng v chuyn v ca xung quanh cng trnh ngm, ng thi xc nh ngay ti ch cc tnh cht ca khi nguyn trng. Hin nay, ngoi cc thit b tin cy c C hc .11 kh nng gim st v d bo s chuyn v ca , cc k thut tnh ton pht trin ti mc m cc cch ng x ca c th c m hnh ho v d on vi tin cy nht nh. Thng10nm1962,HiChcQuct(theInternationalSocietyforRock Mechanics ISRM) c thnh lp o trn c s Hi cc nh a vt l, a cht cng trnh nc o do S.Stini thnh lp t 1951- Hi C hc Quc t tp hp c cc chuyn gia c hc ca nhiu nc trn th gii Cc hi ngh c 4 nm mt ln ca Hi thng bo cc kt qu nghin cu v c hc , ng thi ra phng hng nghin cu trong thi gian ti. Nhng hi ngh gn y ca Hi l ln th VIII nm 1995 Tokyo (Nht), ln th IX nm 1999 Paris (Php) v gn y nht, ln th X Johannesburg (Nam Phi) nm 2003. nc ta, l i tng gn gi ca con ngi t rt lu. T tin chng ta,nhngngiVitc(sngcchykhongtrndi10.000nm)bits dng rt sm: c dng lm cng c lao ng(ru, dao, cuc bng ), lm trang sc cho cc thiu n (cc vng , khuyn tai bng ) hay lm nhc c s dng trong cc sinh hot cng ng (cc n , t v bng ). Trong thi phong kin, nhiu thnh c bng c xy dng vi quy m kh ln nh thnh nh H (cao 5m, dy 3m An Lc, Vnh Lc - Thanh Ho ngy nay,cxytnm1397bngnhngkhixanhln,ckhickchthc 1,7x5,1x2,2mnngti40tn),thnhnhMc(thnhcTuynQuangchnh vung,michiu275m,cao3,5m,dy0,8mcxydngbngongtnm 1592)haythnhcSnTy(cxydngtnm1822cngbngong,mi chiu ca to thnh vung ny cng ti 400m). thkXIX,mtscngtrnhbngcxydng,tntitingy nayvtrthnhnhngthngcnhcatncnhNgmn(cachnhvoi ni c Hu, c xy dng bng nhng khi ln t nm 1802), i Nghin, Thp Bt (bn h Hon Kim, H Ni c xy dng t nm 1867), nh th Pht Dim (Ninh Bnh) BcvothkXX,dovickhaithcm,phttringiaothngvnng lngihiphicnhnghiubitnhtnhvchc.NgiPhp nghin cu o cc hm l khai thc than vng m Hng Gai - Cm Ph (thuc tnh Qung Ninh ngy nay), lm ng hm giao thng trn tuyn ngst xuyn Vit(trongnhngnmcathpnin30),lmnhmythuinaNhim(trong nhngnm1961-1964cngsut160MWvinghmdnncdi4878m, ng knh 3,4m c o xuyn qua o Ngon Mc Sau khi ho bnh lp li, do s pht trin ton din ca nn kinh t qucdn, vic nghin cu v th nghim c hc c ch trng hn, dn dn c hc ngvaitrnhtnhtrongcngcucphttrinkinht,xydngtnc. Ngi ta nghin cu tnh cht ca t , cc qu trnh c hc xy ra khi thi cng cc cng trnh trong v p dng cc phngphp nh gi v phn loi ang c s dng trn th gii trong xy dng cng trnh ngm. Cc nh my thu in lncxydngnhHoBnh(xydngtrongnhngnm1979-1994,cng sut1920MW,pchnnccao128m,gianhmmyckchthc280x22x 53m)hayYaly(xydngt1993-1999,cngsut720MW,pcao69mvgian 12.C hc hmmyckchthc118x21 x42m).Cchml,ccnggiaothngngm cng c xy dng vi nhng bin php k thut tin tin, cch nh gi trng thi khi ph hp vi nhng tin b ca th gii nh hm ng b qua o Hi Vn trn quc l I di gn 6.500m, tit din 10 x 7m p dng cng ngh o hm mi ca o khi thi cng v cch phn loi theo ch s RMR(Rock Mass Rating). Trong tng lai, ngi ta bt u xy dng nh my thu in Sn La, ln nht ng Nam vi cng sut 3600MW v p chn nc cao ti 265m. Cng vi s pht trin ca khoa hc c hc ,nhng ngi lm cng tc c hcVitNamtphp nhau li trong mt t chc gi l Hi C hc Vit Nam c thnhlpvothng10/1984. CccucihicaHic5 nmmtlnnhmtngkt nhngthnhtchnghincu trongnhngnmquavra nhng phng hng hot ng, nghin cu trong nhng nm ti. NhngihignycaHi nhihilnthIIIvonm 1997,lnthIVvonm2002 u c t chc ti H Ni.Nm 1996, Hi C hc Vit Nam c chnh thc cng nhn l thnh vin ca Hi C hc Quc t ISRM. 3. CC PHNG PHP NGHIN CU C HC l mt tp hp c quy lut ca nhiu khong vt. N a dng, khng ng nht,dhngvluntntinhnglrng,khent.Dovy,vicnghincu thng phc tp v kh hn cc vt liu khc. Khi nghin cu thng phn bit khi nim mu v nguyn trng. Mu c coi nh mt th tch m ti khng th pht hin c cc khe nt bng mt thng. nguyntrng(nguynkhi)ccoinhlmtphncavtrit nm trong phm vi nh hng ca cng trnh. Do vy, nguyn trnggm c cc khe nt v vt liu lp nht trong cc khi , chng khng tch khi v tri t, chu nh hng ca cc qu trnh hot ng ni sinh hay ngoi sinh ca v tri t khu vcnghincu.Tnhchtcanguyntrngphthucvothnhphnvtnh cht cacc khong vtto nn , vo c im ca cc h khe nt c trong khi , vo ng thi nc di t v trng ng sut t nhin. nghincuchc,ngitacthsdngnhiuphngphpkhc nhau,nhngnichung,cthgplithnhbanhmchnh:Phngphpoc, quan st trong iu kin t nhin; phng php m hnh v phng php l thuyt. Hnh 0-5.Hm ng b Hi Vn C hc .13 Phng php o c v quan st trong iu kin t nhin gi vai tr quan trng nht.Quavicquanstvoctithcasxcnhcnhngthngsc bn v cc c trng ca qu trnh nh nghin cu trong cc iu kin a - c hc c th nh ng sut, bin dng, chuyn v ca v s thay i ca chng theo cc yuttcngchnh.Tnhngsliusphnloiccchintng,qu trnh nh nghin cu, gii thch c cc c ch chung v bn cht vt l ca chng tin ti tng kt c v mt l thuyt ln thc tin. Trong phng php o c v quan st hin trng, ngi ta lichia ra: -Xc nh cc tnh cht vt l v cc c im cu trc ca khi . -Xc nh cc thng s chuyn v, bin dng ca . -Nghin cu trng thi ng sut trong v s thay i ca n. -Nghincutngtccavivchngvplctrongcngtrnh ngm. Phng php m hnh cng c s dng rng ri nghin cu c hc . N pht hin c vai tr ca cc yu t tc ng khc nhau trong qu trnh nh nghin cu vtm c gi tr ca cc thng s cn thit m cc phng php khc khng th lm c. Tuy nhin, cc m hnh khng th th hin c y cc iu kin achttnhin.Trongphngphpmhnh,ngitacthdngccloim hnh ly tm, m hnh vt liu tng ng, m hnh quang hc Vi mi loi m hnh s c nhng l thuyt ring v bt buc phi tun theo khi s dng chng. Phngphplthuytchophpgiiccbitonchcmctng qut nht, cc iu kin ca bi ton thay i trong mt phm vi rt rng. Tuy nhin, mc chnh xc ca li gii cho bi ton ph thuc vo mc lit k y cc yu t tc ng, cc thng s c bn tng ng vi qu trnh nghin cu v tnh cht ca khi . Mun s dng phng php l thuyt, phi xy dng c mt m hnh ton hc ca hin tng, qu trnh nh nghin cu. Trong c hc , c c mt m hnh ton hc, ngi ta phi l tng ho tnh lin tc ca , trn c s s p dng cc l thuyt cami trng lin tc, ccquy lut ca l thuyt n hi, do, cnbnggiihnTrongcccngtrnhtnhton,cchs,chsthngc xcnhtvicoctithcahocthnghimtrongphnghaytrnccm hnh.Trong nhng trng hp khng c sn li gii, trng thi ng sut bin dng trong c th gii gn ng bng phng php s nh s tr gip ca cc my tnh in t. Ngi ta c th dng phng php sai phn hu hn, phng php phn t hu hn, phng php bin ri rc v phng php phn tring gii cc bi ton c hc . Chng I V CC TNH CHT C BN CA lnhngphnvtchttonnvTrit.Nltphpcamthay nhiu khong vt khc nhau, c cu to v thnh phn khong vt tng i n nh. 1.1. CC KHI NIM C BN V 1.1.1. S THNH TO CC LOI V s hnh thnh cc loi c trnh by rt r rng trong cc gio trnh a cht i cng hay a cht cng trnh. y ch nhc li mt vi im chnh. Theo ngun gc thnh to, c chia thnh 3 loi chnh: magma, trm tch v bin cht. 1.1.1.1. magma c thnh to do s ng cng ca dng dung nham nng chy phunlnttronglngt.Dngdungnhamnylccdungdchsilicatcthnh phn rt phc tp v cha cc loi kh, hi nc khc nhau. Khi dng dung nham phun ln v ng cng li ngay trong lng t th s to thnh magma xm nhp. Do c thnh to trong iu kin p sut cao, s ng cng xy ra t t v u u nn cc khong vt d dng kt tinh, to nn magma kt tinh hon ton, dng khi, cht xt nh granit, gabro Khidngdungnhamtrolnmttvngcnglithstothnh magma phn xut (hay phun tro). Do mt t nhit v p sut thp, nhit thot nhanh nn khng thun li cho vic kt tinh ca cc khong vt, to nn magma dng v nh hnh, c nhiu l rng nh bazan, bt Cc phun tro c thnh to t i c sinh th c gi l phun tro c, cn nu thnh to mi gn y th c gi l phun tro tr. 1.1.1.2. trm tch c thnh to c th theo 3 cch: -Do s lng ng v gn kt ca cc mnh vn (l cc sn phm phong ho ca gc hay cc vn ni la); -Do s kt ta ca cht ho hc c trong nc; -Do s nn cht ca cc di tch ng, thc vt. Tu theo cc cch thc thnh to nh vy m ngi ta cng chia thnh cc trm thch c hc, trm tch ho hc v trm tch hu c. trm tch ch chim 5% khi lng v Tri t nhng n bao ph ti 75% din tch mt t vi cc chiu dy khc nhau (t 3 4km vng Trung , cn 1km vng Xibir v ch t 0,3 0,7km Thi Bnh Dng. C HC .17 1.1.1.3. bin cht c to thnh do s bin i su sc ca magma, trm tchvcbinchtctrcditcngcanhitcao,psutlnvcc cht c hot tnh ho hc. Da vo cc nhn t tc ng ch yu, ngi ta chia ra: Bin cht tip xc xy ra khu vc tip gip gia khi magma nng chy v vy quanh. Nhit cao lm thay i thnh phn, kin trc v tnh cht ca t . Cng xa khi magma, mc bin cht ca gim dn. Bin cht ng lc xy ra di tc ng ca p sut cao khng ch do trng lng cc lp nm trn m cn do p lc sinh ra trong hot ng to sn ca cc qutrnhkinto.Dovy,tbmtnc,rnggimi,slinktgia chng tng ln lm thay i kin trc v cu to ca . Bin cht khu vc thng xy ra di su do tc ng ng thi ca nhit cao v p sut ln lm thnh phn, kin trc ca bthay i. 1.1.2. THNH PHN CA c th c to thnh t mt khong vt ( n khong) hay nhiu khong vtcgnlivinhaubngccchtgnkt(akhong).asccloi u l a khong v nh vy thnh phn ca chng s gm cc khong vt v cc cht gn kt. 1.1.2.1. Cc khong vt to Khongvtlnhnghpchtcaccnguynthohctnhinhaycc nguyn t t sinh c hnh thnh do cc qu trnh ho l khc nhau xy ra trong v Tri t hay trn mt t. a s cc khong vt th rn vc trng thi kt tinh. TheoA.P.Vinogradov,trongtnhinbitkhonggn3000khongvt,nhng trongs,chckhong3050khongvtngvaitrquytnhtrongvic thnh to c gi l khong vt to . Cckhongvttocchiathnhtngnhmvmikhongvtlic nhngcimvcuto,lclinkttrongmngtinhthkhcnhaudnn tnh cht ca chng cng khc nhau. Cc nhm khong vt to chnh: Trong c hc thng khng xc nh thnh phn khong vt y v nh lng.TheoJ.A.Franklin,c6nhmkhongvttochnhnhhngntnh cht c hc ca hu ht cc loi thng gp trong xy dng cng trnh. Cc nhm c nu theo th t gim dn v cht lng c hc: -Nhm thch anh felspat Thch anh l thnh phn ch yu ca granit v hu ht cc loi ct kt. N thng trong sut hoc c mu trng n xm ta thu tinh, cng 7. Felspat l thnh phnchyuca hu ht cc magma vct kt loi arko. N gm plagioclas v orthoclas c mu t hng n trng, m c, rt d vch bng dao b ti. -Nhm lithic / baz Gm cc vn ca magma baz (bazan,gabro), ct ktgrauvac xm tro, amphibolit v cc khong vt baz sm mu nh amphibol v pyroxen. Khi cn ti, cc khong vt ny c cng km hn thch anh mt cht. -Nhm mica Gm cc khong vt dng tm nh biotit (mica en), muscovit (mica trng) v clorit,xuthinnhthnhphnphnhngquantrngcamtsmagmavl thnh phn chnh ca cc bin cht cu to phn phin. Biotit c mu tiu biu t nu n en; muscovit c mu bc v clorit c mu xanh. Tnh phn phin v thng to thnh cc di c hm lng mica cao lm yu cc cha chng. Mica d b tc ng bi cc tc nhn phong ho. -Nhm carbonat Gmcckhongvtnhcalcit,olomitdnhnbitdochngdbvch bng dao, si bt trongHCl long. Chng xut hin di dngcc tinhth, cc ht hayccvnhothchccngkchthcvdokhnnghotan,chngcng thnglximnggnktgiacchtvlpylrng.Cckhongvtnhm carbonat thng c mu trng m n vng sm sng, i khi c mu ti, thm ch l mu en. -Nhm mui Gm mui m, mui kali v thch cao. Chng thng mm yu v do, i khi chyvcthbhotantrongkhongthigianxydng.Cckhongvtnyc khnnghotanvcthnhtotccdungdchmuibin.Mucachng thng t mu m c ti trng pht hng. Tinh th halit c dng khi c trng cn thch cao li c dng si. -Nhm pelit (cha st) Gm cc khong vt nh kaolinit, illit, monmorilonit l cc thnh phn ch yu trong phin st, phin v l sn phm th sinh trong nhiu magma, bin cht vvi.Chngchtmnvdovy,khnhnbit,trkhisuyluntctnh mm yu v mu nu xanh xm thng thng ca chng. Cc khong vt st c kh nng trng n khc nhau, trong monmorilonit trng n mnh nht. Khi m t , cc khong vt c lit k theo phn trm v th t gim dn. Thdgranitcthmttheothnhphnkhongvtlgmfelspattrngti vng sm, 25% thch anh, 10% khong vt cha magne st v 10% biotit. Cu to ca khong vt Khong vt thng gp dng tinh th hay ht. Tuy mt s khong vt c kch thc ln nh thch anh, felspat nhng a s cc khong vt u dng tinh th nh. Cc tinh th khong vt thng c cu to mng l s hnh hc trong khng giancutocavtchtkttinh.Giscmtmngtinhthnhtrnhnh1.1. Phn nh nht ca tinh th c biu din bng cc ng m nt, c gi l nhn cbnhaymngphnt,chngspxplintctheo3trctrongkhnggianto thnh tinh th. C HC .19 Mngphntcctrngbng6 yu t: 3 kch thc ca khung mng a, b, c v3gcgiacctrcX,Y,Zl, v. Tutheoquanhhnhhcgiaccyut camngmcctinhthcchiathnh nhiuhkhcnhaunhtamt(abc; 90o), t phng (a b c; = = = 90o), lc phng (a = b c ; = = 90o, = 120o), lp phng(a = b = c; = = = 90o) Cctinhthkhngchkhcnhauv hnhdngcamngmcnkhcnhau dng cc vt cht nm nt mng. Theo , ngitachiarathnhmngionkhiccnt mng l cc ion mang in tch m hay dng (nh mng tinh th mui m NaCl), mng nguyn t khi mi nt mng l mt nguyn t vt cht (nh mng tinh th kim cng, sfalerit ZnS) hay mng phn t khi nt mng l nhng phn t trung ho v in (nh trong mng cc lin kt hu c). Tuy vy, trong t nhin rt hay gp cc mng hn hp nh mng ion phn t. Cc khong vt to cng hay l loi mng ny. Lc lin kt trong mng tinh th. Lclinkttrongmngtinhthcbnchtllctnhin,sinhradotc ng tng h ch yu l ca cc in t ho tr ca nguyn t. Do s phn b cc in t trong nguyn t v phn t ca cc tinh th khng nh nhau nn cc lc lin kt trong cc tinh th khong vt cng khc nhau. Ngi ta chia ra mt s loi lin kt sau: -Lin kt ion thng thy cc mng ion, ngha l ti cc nt mng l cc ion dng hay m. Lc lin kt gy ra do lc ht gia cc ion mang in tch tri du. Lc ny t l nghch vi khong cch gia cc ion v t l thun vi cc in tch ca chng. -Linktnghotrthngthyccmngnguynt.Lclinkt sinhradotcngtraoiintgiahainguyntnmhaint mng rt gn nhau. -Linktcarbonlthdcincaccloilinktny(nhkim cng v mt vi khong vt khc). -Lin kt phn t thng thy cc mng phn t. Cc phn t trung ho v in nhng s sp xp cc in tch trong chng li khng hon ton i xng nn s lin kt gia cc phn t l lc tnh in rt yu nh lc Vander Vaals, sinh ra khi chng gn nhau. bn ca nhng tinh th c lin kt kiu ny rt km. -Linktkimloictrngchotnhchtcatinhthkimloi.Nhng nguyntkimloisaukhimtinttrthnhcciondngnm Hnh 1.1. Mng khng gian ca tinh th. cc nt mng, cn cc in t tch ra nm khong khng gia cc nt. Gia cc in t, ion dng lin kt vi nhau bng cc in lc. Chnh cc lc ny gii thch cho bn ca vt rn. Do mng tinh th ca mt vi khong vt c th l hn hp nn lc lin kt ca chng cng khng phi ch l mt loi. C th theo hng ny th l lin kt ion, cn theohngkhcthcthllinktphnt(nhmolibenit,grafit).iuny lm pht sinh tnh cht d hng ca cc tinh th. Mt s c trng ca khong vt: -Trng thi vt lascckhongvtudngkttinh,trongccnguynthayion cspxptheomttrttnhtnh,tothnhmnglikhnggian lmkhongvtchnhdngbnngoinhtnh.Mtskhongvtv nh hnh do khng c cu trc mng tinh th khng gian nn chng khng c hnh dng bn ngoi nht nh, to nn tnh ng hng ca khong vt: tnh cht ca khong vt theo mi phng c th coi l bng nhau. -Hnh dng tinh th Tutheosphttrintrongkhnggiancamngtinhth,khongvtc th c dng hnh lng tr, hnh que, hnh kim khi tinh th khong vt ch phttrintheomtphng;dngtm,vy,lkhitinhthkhongvt phttrintheohaiphnghaydnght,cckhitinh thphttrintheo c ba phng. -Mu sc v vt vch Mu ca khong vt l do thnh phn ho hc v cc tp cht trong n quyt nh.Theo,ngitachialmkhongvtmusng(khngmu,trng, xm sng, vng hng) v khong vt mu sm (en, xanh, nu v cc mu ti khc). Vtvchlmucabtkhongvtlitrntmstrng,nhmkhic von.Thngthmucakhongvtvcavtvchlgingnhau nhngcngcnhngkhongvtlikhngthhinnhvy:Khongvt hmatitcmuen,xmthpnhngmucavtvchlilmuhay khong vt pyrit c mu vng thau nhng vt vch li c mu en. - trong sut v nh trongsutcakhongvtlkhnngkhongvtchonhsngxuyn qua.Theo,ngitachiathnhccmctrongsut(nhthchanh, muscovit), na trong sut (nh thchcao, sphalerit), khng trong sut (nh pyrit, magnetit).nhcakhongvtlsphnxmusctrnmtkhongvtkhinh sng chiu vo. Ngi ta chia thnh nh kim v nh phi kim (nh nh thu tinh, nh x c, nh m, nh aamatin). -Tnh d tch (ct khai)Tnh d tch l kh nng tinh th ca mt vi khong vt c th tch ra c theonhngmtphngsongsongvinhaukhichutcdnglc.Ccmt phng ny cng c gi l mt tch hay mt ct khai. C HC .21 Theo O. Brave (1848), ngi sng lp ra l thuyt cu to mng ca tinh th th mt ct khai l mt c mt nt ln nht v khong cch gia cc mt cng l ln nht. Trong mt mt ca mng tinh th (hnh 1.2), k cc hng OA, OB, OC. Mt ntdynhtlhngOA(khongcchgiaccntlbnht).Khiu khong cch gia cc mt song song lin tip theo cc hng trn, tng ng l d1, d2 v d3; v khong cch gia cc nt theo cc hng trn tng ng l a1, a2 v a3 th c th d dng nhn thy l: a1d1=a2d2=a3d3=ad (1.1) ngha l tch ca khong cch gia cc nt mng theo mt hng no v khong cch gia hai mt song song lin lip theo hng lun l mt hng s. Vvy,khikhongcchgiahaimt song song cng ln (trong khi khong cch gia ccntmngcnggimnghalmtnt cngdy)thlclinktgiachngcng gim,chngcngdtchxanhaukhichutc dng lc. mngtinhthnhtrnhnh1.2,mt ct khai s l mt MN, trng vi hng OA. Tuy nhin, lc lin kt gia cc nt mng khng ch ph thuc vo khong cch gia chng m cn ph thuc vo s tng tc giachng,nghalcnphitnhncclc lin kt ho hc. Tnhchtctkhaicngcthgiithch bng thuyt nng lng b mt. Theo V.. Kuznexhov th mt ct khai s trng vi mt c nng lng b mt b nht. Nng lngb mt c th coi l nng lng d trn mt n v din tch hay l lc cn thit t vo mt n v chiu di tch lp trn mt (vi cc cht lng, nng lng b mt c gi l sc cng b mt). Tu theo mc d tch ca cc khong vt m ngi ta c th chia thnh d tch rt hon ton (nh mica, mui m), hon ton (nh calcit), trung bnh (nh felspat),khnghonton(nhapatit,olivin)vrtkhnghonton(nh corinon, magnetit). -Vt v Vt v l dng bt k ca mt khong vt khi b ph hu.Tutheohnhdngcavtv,ngitachiathnhvtvphng(khi khong vt b v theo cc mt d tch, c trng cho cc khong vt c tnh d tch cao), vt v v s (nh thch anh), vt v nham nh (khi mt vt v lm chm, khng bng phng nh cc khong vt ng, bc) v vt v t (khi b v, khong vt vn nh t, nh khong vt kaolinit). - cng cng l kh nng chng li tc dng ca ngoi lc ca khong vt, c trng cho bn cc b ca n.d2BCAd3d1oM NHnh 1.2. Mt mt ca mng tinh th. Trongthct,thngdngcngtngi,nghalsosnhcngca khong vt vi 10 khong vt chun do F. Mohs chn ra t th k XIX. Vic so snh c thc hn theo nguyn tc khi c xt hai khong vt vi nhau, khong vt no cng hn s li vt xc trn khong vt kia. Cc khong vt trong thang cng ca Mohs c coi l mm nht ( cng 1) ti cng nht ( cng 10) nh sau: 1- Talc6- Orthoclas 2- Thch cao7- Thch anh 3- Calcit8- Topaz 4- Fluorit9- Corinon 5- Apatit10- Kim cng. Ngoi ra, ngi ta cn dng cng ca mt s vt ph bin nh mng tay ( cng2,5),mnhknh(5,5),lidaothp(6,5)ddngxcnhcngti thc a. -T trng Tutheosthayittrngcacckhongvt,ngitachiathnh khongvtnngkhittrng>4nhpyrit,magnetit;khongvttrung bnh khi t trng t 2,5 4 nh thch anh, calcit v khong vt nh khi t trng < 2,5 nh thch cao, orthoclas a s cc khong vt thng c t trng t 2,5 3,5. -Tnh d hngDhngltnhchtphthucvohngcatinhth:theocchng song song vi nhau th tnh cht ca n l nh nhau, nhng khi xt theo cc hng khc nhau th tnh cht ca n li thay i. Tnh d hng ca khong vt c th gii thch theo l thuyt cu to mng ca tinh th. Trnhnh1.2,theocchngOA,OB,OCmtnt(slngnttrn1 n v chiu di) l khng ging nhau. Mt dy nht l theo hng OA, tha nht l hng OC, do vy lc lin kt gia cc nt mng theo cc hng cng s khng nh nhau lm tnh cht ca khong vt theo cc hng khc nhau s khc nhau. Vi cc hng song song, chng c cng mt nt v do vy, tnh cht ca chng hu nh khng thay i. Ngitathngnsdhngcngcakhongvtvhsd hng l t s gia gi tr ln nht v nh nht ca mt ch tiu theo cc hng khc nhau c dng th hin tnh d hng ca khong vt. Th d: Khong vt rt d hng v cng l disthen vi h s d hng bng 3,13. Ngoi cc tnh cht trn, khong vt cn c mt s tnh cht khc nh kh nng sibtviHCl10%,tnhnhi,khnngunconghaydtmng,ttnh,tnh phng x 1.1.2.2. Cht gn kt C HC .23 Trong a khong hay vn, cc khong vt hay cc ht c gn li vi nhau bng cc cht gn kt. Cc loi cht gn kt Tutheotnhcht,thnhphncachtgnktmngitachiaraccloi cht gn kt sau: -Cht gn kt silic gm SiO2 hay SiO2.nH2O -Cht gn kt carbonat gm calcit CaCO3, sierit FeCO3 -Cht gn kt sulfat nh thch cao CaSO4 -Cht gn kt c cha st nh hematit Fe2O3, limonit 2Fe2O3.3H2O -Chtgnktcchastgmcckhongvtstnhkaolinit Al2O3.2SiO2.2H2O, illit -Cht gn kt t bitum hay cc cht khc. Theo th t k trn, bn ca cc cht gn kt gim dn nn cc c gn kt bng silic l loi cng v bn vng nht trong cc trm tch. Cc cht gn ktcngcmuscrtctrng:Silicvvithngcmuxmnht,sieritc mu da b, hematit c mu , cn limonit li c mu nu. Cc kiu gn kt Tutheotngquangiaccchtgnktvcchtcgnktm ngi ta chia thnh 3 kiu gn kt: -Gn kt kiu tip xc khi cht gn kt ch c ch tip xc gia cc ht (hnh 1.3a). -Gnktkiulpyhaylrngkhichtgnktlpylrnggia cc ht (hnh 1.3b). -Gn kt kiu bazan hay c s khi cht gn kt trn y trong khi lm cc ht khng tip xc vi nhau (hnh 1.3c). a) b) c) Hnh 1.3. Cc kiu gn kt.a) Kiu tip xc; b) Kiu lp y; c) Kiu bazan. Theo th t k trn, khi vi cng mt loi khong vt v cht gn kt, bn ca tng dn. 1.1.3. KIN TRC CA Kin trc l tng hp cc c trng thnh to ca c xc nh bng mc kt tinh; dng, kch thc ht v quan hlnnhaugiaccphntonn, nghalgiacckhongvttov dung nham trong magma hay cht gn kt trong trm tch vn. 1.1.3.1.Theomckttinh,ngita chia ra: Kintrctontinhhaykintrc ht,ctrngcholoinmdisu, kttinhtrongiukinthunli:qu trnh ng ngui xy ra t t, cc tinh th cthigianlnln,tonntrong gmtonnhnghtkttinhcth nhn r c bng mt thng (hnh 1.4). Kintrcporphyrtothnhkhi iukinkttinhkhngthunli:phn magmanglidngthutinh,trn nncnilnnhngtinhthlnca khong vt to . gm c cc khong vt dng kt tinh v nhng tinh th nh mmtthngkhngnhnthyc (hnh 1.5). Kin trc n tinh gm nhng tinh thrtnhchnhnthycquaknh hinvi,xyrakhidngdungnhamb nguilnhnhanhtrnmtt,tinhth khng thi gian hnh thnh, ch to c nhng tinh th rt nh (hnh 1.6). Kintrcthutinhtothnhkhi iukinkttinhrtkhngthunli. Dng dung nham b ngui lnh rt nhanh to thnh mt khi thu tinh c xt. Kin trc ny thng thy khi dng dung nham phun ln t lng t di y bin. 1.1.3.2. Theo kch thc ht kt tinh, Hi C hc Quc t (ISRM) chia thnh mt s loi kin trc sau: Kin trc ht rt th khi ng knh ht > 60mm.Kin trc ht th khi ng knh ht t 2 60mm.Kin trc ht va khi ng knh ht t 0,06 2mm.Kin trc ht mn khi ng knh ht t 0,002 0,06mm.Hnh 1.4. Kin trc ton tinh( granit c cha cc ht ln orthoclas, thch anh v biotit) Hnh 1.5. Kin trc porphyr Hnh 1.6. Kin trc n tinh C HC .25 Kin trc ht rt mn khi ng knh ht < 0,002mm.TrongtiuchunVitNamTCVN57471993,kintrccacphn chia theo kch thc ca cc ht vi cch gi tn v kch thc ht hi khc: Kin trc tng khi kch thc ht > 300mm Kin trc cui (dm) khi kch thc ht t 150 300mm Kin trc si (sn) khi kch thc ht t 2 150mm Kin trc ht ct khi kch thc ht t 0,06 2mm Kin trc ht bi khi kch thc ht t 0,002 0,06mm Kin trc ht st khi kch thc ht t < 0,002 mm. 1.1.3.3. Theo dng v mc ng u ca ht Theo hnh dng ca htkt tinh, tu theo tngquan gia 3 chiu kch thc ca ht m ngi ta chia thnh kin trc ng thc (khi kch thc 3 trc gn nh nhau), kin trc dng tm (khi c 2 trc di v 1 trc ngn) v kin trc dng si (khi c 2 trc ngn v 1 trc di). Tu theo hnh dng ca ht kt tinh sau khi b mi mn m ngi ta c th chiathnhkintrchtgccnh,nagccnh,natrncnh,trncnhhocrt trn cnh. Tu theo mc ng u ca cc ht kt tinh m ngi ta li chia thnh kin trchtu(khicchtckchthcgngingnhau)vkintrchtkhngu (khi cc ht c kch thc rt khc nhau). 1.1.4. CU TO CA Cutolnhngcimvsspxptrongkhnggiancanhngthnh phn to nn v mc lin tc ca chng. 1.1.4.1. Trongc hc , theo s nh hngca cc khongvt trongkhnggian th c mt s cu to chnh l: Cutokhictothnhdoccthnhphntonnspxpkhng theo mt trt t, mt qui lut no c, to nn mt khi cht xt. Cu to ny c trng ch yu cho magma, khi cc dng dung nham tro ln ri ng c li. bin cht v trm tch cng thy c cu to ny. Dosspxpmtcchngunhincaccthnhphntonn,nntheo cc hng khc nhau, tnh cht ca khi coinh lging nhau- c tnh cht ng hng. Cu to phn lp c to thnh do s lng ng lin tip ca cc lp c thnh phn v kch thc ht khc nhau trong trm tch hay do s ng cng ca cc di theo phng dch chuyn ca dng magma trong magma hay do s bin cht cao ca cc di c trc trong bin cht. Tu theo chiu dyca lp m ngi ta chia thnh phn lp mnh, mng, trung bnh v khng phn lp (to thnh khi). Cu to ny c trng cho trm tch. Cu to phn phin c to thnh do s bin i ca trong qu trnh lm cht haycc qu trnh kin to gy ra p sut cao, nhit ln. Trong c nhng di di song song vi nhau, chiu dy ca cc di ny nh. Trongcutophnphin,ngitalichiathnhphnphinnguynsinhv thsinhkhibmtcclpphnphinvnsongsonghayblchlcisovi hng phn lp chnh ban u. Cu to ny c trng cho bin cht. 1.1.4.2. Theo mc lin tc ca s sp xp cc thnh phn to nn , ngi ta chia hai loi cu to chnh: Cutochtxtkhiccthnhphntonnspxpchtxtvinhau, trong hu nh khng c l rng. Cu to cht xt thng c trng cho magma v bin cht. rng (l t s % gia th tch ca l rng trong v chnh th tch ca mu ) ca cc loi ny thng ch t 0,8 1,2% (theo N.I.Xhaxhov). Cutolrngctothnhkhisspxpngunhin,khngchtch ca cc thnh phn to nn . Trong c rt nhiu l rng gia cc thnh phn tonnhaytothnhdosthotkhvhinctdngdungnhamca magma. Cutolrngthngctrngchotrmtch.Viccny,rng thng rt ln, c th t 3 39% vi ct kt hay t 0,6 33% vi vi, olomit (theo N.I. Xhaxhov). Ngoicccutotrn,trongmagma,ngitacnggilcutohnh nhnkhitrongcclrnglichacckhongvtthsinhkhchaycutodng bt, dng x khi trong c rt nhiu l rng lm xp v nh (hnh 1.7). 1.1.5TNH KHNG NG NHT V D HNG CA ltphpcanhiukhongvt.Bnthnmikhongvtctnhd hng v s sp xp chng trong khng theo mt trt t, mt qui lut no nn v mt thnh phn khongvt, l mt vt th khng ng nht. cthnhtodosgnktcc khongvtkhcnhautrongtrmtchhay dosngnguicacckhongvttrong dungnhamnngchycamagma,ms spxpcchtkhongvttrongkhil hon ton ngu nhin nn v mt sp xp cc ht trong cng l khng ng nht.Khi thnh to , cc l rng c hnh thnhmtcchhontonngunhin,btk vmtcutovkchthc.Cclrngc th lin h vi nhau v cng c th ring bit nu nhng ch khc nhau trong khi , rng ca cng khc nhau, ngha l khng ng nht v mt rng. Hnh 1.7. bazan dng bt C HC .27 Vic lm cht ph thuc vo chiu su. cng nm di su th do p lc cacctngnmtrn,cngclncht.Mclmchtcngphthuc vo cu to v cc hotng kin to xy ra ticc v tr khc nhau trong khi . Cc khe nt kin to c to thnh cng khng phi l ging nhau trong tt c mi im ca khi . V vy, khng ng nht v mc lm cht v tnh cht nt n ca n. Do chu nh hng ca nhiu mt v s khng ng nht nn th hin tnh khng ng nht qua cc biu hin khc nhau, nhng r nht l tnh d hng, l s khc nhau v cc ch tiu tnh cht ca khi xt theo cc hng khc nhau. Vi cc trm tch v bin cht, s d hng th hin s khc nhau v tnh chtkhixttheohngsongsonghayvunggcviccmtphnlphayphn phin ca . Ngi ta dng h s d hng l t s gia mt ch tiu tnh cht no ca xc nh theo hng vung gc vi mt phn lp hay phn phin v chnh ch tiu khi xc nh theo hng song song vi mt phn lp hay phn phin ca . // XXkd=(1.2) trong : X l mt ch tiu tnh cht no ca . Vimagma,sdhngchxyrakhicmtlpkhongvtcnh hngtheomtphngno,miunylihimxyratrongqutrnhthnh to magma nn thc t, ngi ta coi magma l nhng khi ng hng. 1.1.6. MT S LOI THNG GP Theongungcthnhto,cchiathnhccmagma,binchtv trm tch. Trong mi loi , tu theo v tr, iu kin thnh to v kch thc cc ht m ngi ta li chia ra nhiu tn khc nhau. Cc nh a cht th khi phn loi, hay nng v ngun gc hnh thnh ca cc loi , cn i vi nhng ngi nghin cu c hc , ngi ta thng da trn s quan st nh hng n thun v c ht ca nhng thnh phn to nn . 1.1.6.1. magma magmacthnhtodosngcngcadngdungnhamnngchy (magma) phun ln t trong lng t. Thnhphnchyucamagmalfelspat(khong60%),amphibolv pyroxen (khong 17%), thch anh (khong 12%), mica (khong 4%) v cc khong vt khc. Nu theo hm lng SiO2 c trong th ngi ta chia magma thnh loi magmaaxit(khilngSiO2>65%),magmatrungtnh(khilngSiO2=55 65%),magmabaz(khilngSiO2=4555%)vmagmasiubaz(khi lng SiO2 < 45%). Tu theo t l cc khong vt sm mu c trong m cc magma c th c mu sng (thng l magma axit) hay mu sm va, qu sm (vi magma baz v siu baz). Tutheovtrkttinhcakhimagmatronglngthaytrnmttm ngi ta chia cc magma thnh loi magma xm nhp nh granit, iabas, gabro hay magma phn xut (phun tro) nh bazan, ryolit magmathngccutokhi,kintrckttinhhocthutinh,rng thp (thng < 2%), bn cao tr khi b phong ho. Cc magma c chia thnhccloitheocht:Viccmagmahtth(chtinhnhthng> 2mm) th cgi l granit haygabro tutheo thuc loi axit haybaz. Vi ccmagmahtva(0,062mm)thtothnhtngnglmicrogranitv iabas.Viccmagmahtmn(30%.bnnncaanhydritkhong60 80MPa.Thch cao c to thnh do kt qu hp nc ca CaSO4, c mu trng hay xm,vng,nukhiblncctpcht.Kintrchtth.bnnhhn20MPa. Thch cao c dng lm phn, vt liu trang tr trong xy dng hay b bt trong y t. Nhm trm tch hu c c thnh to do s tch t v nn cht ca cc di tch ng thc vt. T cc di tch ng vt s to thnh cc loi nh vi v Hnh 1.14. silvinit (vng Solikamsk Lin X c). s, vi san h, phn nh trnh by trong nhm trm tch carbonat. T cc ditchthcvtstothnhccloitrmtchnhiatomit,opoka(silic),than bn hay than 1.2.6.3. bin cht bin cht c thnh to t cc magma, trm tch hoc bin cht tn ti trc do s tc ng mnh m ca nhit cao v p sut ln. Bin cht tip xc xy ra do s nung nng cc khi gn k ca dng magma xm nhp.Bin cht ng lc xy ra do s ng sut cc b qu ln lm bin dng, nt n v v vn . Bin cht khu vc tc ng trn mt din tch rng ln bng s tng ng thi ca c nhit v p sut. gneis(loiparagneishay orthogneis)ctothnhdos binchtcatrmtchhay magmabanu.Khibincht chuyntipdntgranitn gneisthscloi granitogneis.gneisccuto gneisinhnh:mtdikhongvt sngmugmthchanh,felspatri tipnmtdikhongvtsm mugmbiotit,horblend.gneis c bn cao, t 80 180MPa (hnh 1.15).Hnh 1.15. gneis. Khihmlngmica,cloritvcckhongvtdngtmkhctrongkh nhiu(thngkhong>50%)thstoratrongtnhphnphinvphnlp mng gi l cc phin (hnh 1.16). Tu theo hm lng khong vt no chim u thtrongphinmngitacthgpphinmica,phinst,phin amphibol Khi trong thnh phn ca phin khng c mica m ch gm nhng ht mn s to thnh ngi, cng v c th tch ra thnh tng tm. C HC .33 Hnh 1.16. phin. i vi cc cu to khi, tu theo thnh phn ban u ca chng m khi b bin cht c th to thnh cc loi rt khc nhau. vi khi b bin cht s to thnhhoaviccmusckhcnhaucthdngtctnghaylmvtliu trang tr (hnh 1.17). quarzit c to thnh do ct kt thch anh b bin cht c bn rt cao (ti 350MPa), lm nn cho cc cng trnh xy dng rt tt. sng l loi bin cht t cc khng phn phin vi cc ht rt mn cng c s dng nh mt loi vt liu xy dng, lm nn cng trnh xy dng. Tmtsthnggptrongtnhin,tiu ban phn loi ca Hi C hc Quc t (ISRM) nhnghacctnchyuvtmttchng trongbng1.1.TrongChc,phicgi tn theo cc tn gi trong bng tm tt ny. 1.2.CC TNH CHT C BN CA Tphpcctnhchtcat,trckia thnggiltnhchtc-lnghalgmtnh chtchcmctrngbngmtschtiulin quanntnhchtchccanhbn,tnh chtbindng,tnhchtlubinvtnhchtvt l nh trng lng th tch, rng, m ca . Trongnhngnmgny,ngoinhngtnhcht trn, cc c trng khc ca cng c nghin cu tmnhtnhchtnhit(viccctrngnh dnnhit,ginnvnhit),tnhchtint (nhccctrngintrsut,nhimt,t cm), tnh cht m hc (nh cc tc truyn sng n hi, sut cn sng) nn thut ng tnh cht c-ltrntrnnkhngyvkhngchnh xc. Mt khc, cc hin tng c hc, nhit hc, in t hc, m hc u thuc v vt l hc, ngha l cc tnh cht c hc, nhit hc, in t hc u l nhngphnngcatrcnhngtrngkhc nhaucavtlhc;chclmtphncavtl hcnnkhngthngangnhaunhmttnhcht c - l V vy, hp l v chnh xc hn, nn gi tp hp cc tnh cht ca l cc c trng ca tnh cht vt l ca . Nh vy, ni n tnh cht vt l ca , ngha l ni n cc ch tiu c trng cho hm lng tng i ca cc pha trong , cc ch tiu ca tnh cht c hc, tnh cht nhit, tnh cht in t, tnh cht m hc, tnh cht phng x ca . Hnh1.17.TngVn Milobnghoa(tm thy nm 1820). T cui nhng nm 1970 ca th k trc, quan nim ny c mt s nh nghin cu c hc Lin X c nh I.A. Turchaninov; M.A. Iofix; E.V. Kaxparjan nuratrongcccngtrnhnghincucamnhcngnhnm1991,trongcng trnhcngb,mtsnhnghincuchccaPhpnhJ.Grolier,A. Fernandez, M Hucher v J.Riss cng c nhng kin tng t. nh ngha cc tn ch yu theo ISRM (1979) Nhm ngun gc Trm tch Bin cht Magma Lp Phn phin Khi th nt Cu to Mnh vn (ht vn) Kt tinh hay thu tinh (n tinh) Cc khong vt sng mu nh thch anh, felspat, mica v cc khong vt ging felspat Cc khong vt sng v sm mu Cc khong vt sm mu C ht, mm Kin trc Cc ht l thch anh, felspat v khong vt st 50% cc ht l carbonat 50% cc ht l magma ht mn ho hc, hu c Thch anh, felspat, khong vt sm mu hnh kim Ph thuc m Axit Trung tnh Baz Siu baz Ht rt th Pegmatit Ht th Ht l cc vn Ht trn cnh: cui kt Ht gc cnh: dm kt Cui kt cha vi Ht trn cnh: cui kt. Ht gc cnh: dm kt ni la Granit iorit Gabro Ht va Ct kt: cc ht ch yu l cc vn khong vt Ct kt thch anh: 95% thch anh l rng hay gn kt Arko: 75% thch anh, ti 23% felspat, l rng hay gn kt Grauvac: 73% thch anh, 15% nn ht vn mn, mnh vn v felspat Ct kt cha vi Micro - granit Micro-iorit iabas Ht mn Ht rt mn Argilit phin: argilit phn phin Bt kt: 50% cc ht mn St kt: 50% cc ht rt mn v iSt kt cha vi ( phn) T r o n i l aTuf ni la Cc mui (halit, anhyrit) Thch cao vi olomit bn Than non Than Gneis: xen k cc di khong vt dng phin v dng ht Quarzit hoa Granulit sng Amphibolit Ryolit Anesit Bazan Pyroxe-nit v Perio-tit Serpenti-nit 60 2 0,06 0.002 Thu tinh sng silic Thu tinh ni la: obxiian, du, tachylit. 36.CH Bng 1.1 C hc .37 Trong hng lot cc c trng trn, tu theo tng yu cu c th m ngi ta c th xc nh v s dng cc c trng khc nhau ca . Trong phn ny ch nu ln cc c trng, cc tnh cht c bn nht ca thng c dng nht trong khi tnh ton, thit k v xy dng cng trnh. 1.2.1. MTSCHTIUCTRNGCHOHMLNGCCPHA TRONG gm c 3 pha: rn, lng v kh. Tu theo t l hm lng cc pha c trong m lm c th nng hay nh, m hay kh; cht xt hay xp rng phn bit cc c tnh ny, ngi ta thng dng mt s ch tiu sau: 1.2.1.1. Trng lng ring v khi lng ring Trnglngringcaltrnglngmtnvthtchphacngca n. V tr s, trng lng ring c tnh bng t s gia trng lng phn cng ca vthtchcan.Trnglngringthngckhiuls,nvtnh thng l kN/m3 hay MN/m3. s=ssVQ (1.3) trong :Qs l trng lng phn cng ca . Vs l th tch phn cng ca . Trng lng ring ca ph thuc vo trng lng ring v t l th tch ca cc khong vt to c trong . Bit c cc khong vt to v t l th tch ca chng trong , s tnh c trng lng ring ca theo cng thc: = = n1 ii s sV .i(1.4) trong :sil trng lng th tch ca khong vt to th i. Vil t l th tch ca khong vt to th i trong . nl s lng khong vt to c trong . ng thi vi trng lng ring, trong thc t cn dng mt i lng gi l t trng, l t s gia trng lng ring ca mt loi no so vi trng lng ring canc.Ttrnglmtilngkhngcthnguynvcxcnhtheo cng thc: ns= (1.5) trong :l t trng ca . nl trng lng ring ca nc. 38.C hc Thc t thng kh xc nh c trng lng ca vt (l sc ht ca Tri t vo vt y ti mt ni no ) m ch d dng xc nh c khi lng (l s lng vt cht c trong vt hay chnh xc hn l i lng xc nh qun tnh ca vt y) ca vt bng cc cch cn khc nhau. Ti cc v tr khc nhau th trng lng ca vt khng ging nhau, trong khi khi lng ca vt lun khng i. Quanhgiatrnglngvkhilngcamtvtcxclptheol thuyt ca vt l s cp: P = m.g (1.6) trong :Pl trng lng ca vt. ml khi lng ca vt. gl gia tc ri t do, thay i theo v tr ti im ang xt trn mt t. V vy, bit khi lng ca mt vt, s d dng tnh c trng lng ca n. Theo V.N. Kobranova, gi tr trng lng ring ca mt s loi khong vt v trm tch c th thy trong bng 1.2. Bng 1.2 Tn khong vt v s, kN/m3 Tn khong vt v s, kN/m3 Anhydrit Biotit Calcit olomit Halit Kaolinit Magnetit Monmorilonit Olivin Orthoclas 28 30 26,9 31,6 27,1 27,2 28 29,9 21 22 26 26,3 49,7 51,8 20 25,2 31,8 35,7 25 26,2 Plagioclas Pyrit Thch anh Bt kt Ct kt vi phn olomit St kt 26,1 27,6 49,5 51 26,5 26,6 26,5 27,3 26,4 26,8 27,0 27,4 26,3 27,3 27,5 28,8 25,5 27,0 Khi lng ring ca l khi lng mt n v th tch pha cng ca n. V tr s, khi lng ring c tnh bng t s gia khi lng phn cng ca v thtchcan.Khilngringthngckhiuls,tnhbngg/cm3hay t/m3. sssVm = (1.7) C hc .39 trong : ms l khi lng phn cng ca . Cng nh trng lng ring, khi lng ring ca ph thuc vo thnh phn khong vt v t l ca cc khong vt to c trong . Gia khi lng ring v trng lng ring c mt s lin h: s=g. s(1.8) Nu so snh khi lng ring ca vi khi lng ring ca nc th s c mt i lng gi l t khi, thng k hiu l D: D = ns (1.9) trong : nl khi lng ring ca nc. T khi l mt i lng khng th nguyn. xcnhkhilngringca,phitnhckhilngvthtch phncngtrong.Munvy,ngitacthdngnhiuphngphpxcnh khc nhau: -Dng bnh o th tch Bnh o th tch l mt bnh bng thu tinh c hp v di (ng knh c bnh l10mm,di180200mm)dungtchkhong120150cm3.Trncbnhccc vch chia chnh xc ti 0,1cm3. Phn di ca bnh phnh to ra. Chn 2 cc nh xc nh khi lng ring khong 100g, em gi trong ci chy ng ri sng qua ry c ng knh l 2mm. Phn bt cn li trn mt sng li em gi v tip tc sng. Ly khong 180g bt sng em sy nhit 105 110 5oC ti khi lngkhngi.Saukhong2h,lyra,nguitinhittrongphngrit trong bnh ht m. cht lng (nc ct hay du la) ti ngn di vch 0 ca bnh o. Tu theo tnh cht ca m cht lng c th l nc ct khi khng b ho tan hay du la,axtnkhicchaccmuitanctrongnc.Ccgitchtlngtha hay dnh trn c bnh phi c thm kh bng giy lc. Cn ly 30g bt sykh bngcn phn tch, ri vo bnh o ti khi nomcchtlngdnglntivchdu20cm3haymtvchnogntrnc bnh th thi. Ch khng bt bm vo c bnh. Quaynhbnhxungquanhtrccanbtkhtrongbnhnilnhaycho vo bnh chn khng c p sut bng 20 200mmHg trong 30 ui ht kh ra. Cn phn bt cn li. Khi lng ring ca s c xc nh theo cng thc: 40.C hc Vm - m

cs = (1.10) trong :m l khi lng bt sy kh ti khi lngkhng i. mc l khi lng bt cn li sau khi th nghim. Vl th tch cht lng dng ln trong bnh o. Khi lng ring c xc nh bng tr s trung bnh s hc gia hai ln o. Kt qu th nghim ph thuc rt nhiu vo vic y kh ra khi bt . -Dng picnomet (bnh o t trng) Phng php ny hay c dng v kt qu kh chnh xc. TheoOCT746555caLinXcthpicnometcthlmtbnhthu tinh hnh cu c di c ngn nh du th tch hay l mt bnh thu tinh hnh cu c ngn, np c rnh mao dn, c dung tch 25, 50 hay 100ml. Vi loi bnh cu c di th dung tch danh ngha t c khi mc cht lng trng vi ngn trn c bnh, cn vi loi bnh cu np c rnh mao dn, th l khi trn u rnh c thy cht lng. Cch xc nh khi lng ring nh sau: Vic chn v chun b mu cng lm tng t nh phng php trn. Ra sch bnh o, lau kh v em cn trn cn phn tch, c khi lng mo. y nc ct vo bnh o v cho nc ct c nhit th nghim (18, 20 hay 22oC) em cn bng cn phn tch c khi lng m1. ht nc ct ra, lau sch v kh bnh o ri vo bnh khong 10g bt sy kh ti khi lng khng i, ri em cn, c khi lng m2. y ht kh ra khi bt , ngi ta cht lng khng ho tan (nc ct, dula,cntutheotnhchtcatngloi)tikhong1/2hay2/3thtch bnh o. un si trn bp ct (khng cho cht lng tro ra ngoi) trong khong 20 30. Vic y kh ra khi bt cng c th thc hin trong bnh chn khng. Lmnguibnhotrongchunc,emhtchnkhngvchtlngti vch ngn tht chnh xc. Lau kh bnh o ri em cn, c khi lng m3. Khi lng ring ca s c xc nh theo cng thc: ( )( ) ( )2 3 o 1cl o 2sm m m m. m m

= (1.11) t m2 mo = m C hc .41 3 1cl2 3 o 1clsm m m. m

m m m m. m

+=+ = (1.12) trong :cllkhilngringcachtlngemthnghim,nthayi theo nhit th nghim. Vi nc ct: t = 13 17oCcl = 0,999 t = 18 23oCcl = 0,998 t = 24 27oCcl = 0,997 t = 28 31oCcl = 0,996 Vichtlngkhc,trckhiemthnghim,phixcnhtrctipkhi lng ring ca n ti nhit th nghim v khng nn ly theo gi tr ca cc bng, v s lm kt qu th nghim km chnh xc. Khi lng ring c xc nh theo tr s trung bnh s hc gia 2 ln o, ly ti 2 s l. Sai s cho php gia 2 ln o l 0,02g/cm3. Ngoihaiphngphptrn,ngitacncthxcnhkhilngring bng phng php Hli, phng php cn thu tnh 1.2.1.2. Trng lng th tch v khi lng th tch Trng lng th tch ca l trng lng mt n v th tch ca n m t nhin hay xc nh no . V tr s, trng lng th tch c tnh bng t s gia trng lng ca mu (bao gm c nc v kh trong cc l rng) v ton b th tch ca n (k c cc khe nt v l rng). Trng lng th tch thng c k hiu l , n v tnh thng l kN/m3 hay MN/m3 : r sk n sV VQ Q Q

+ + += (1.13) trong : Qnl trng lng nc c trong mu . Qkl trng lng kh c trong mu . Vrl th tch l rng v khe nt trong mu . Nu b qua trng lng kh v coi trng lng ton b mu l Q, th tch ton b mu l V, th c th vit: VQ

VQ Q

n s=+= (1.14) Trnglngthtchcakhngchphthucvothnhphnkhongvt to , m cn vo cu to ca n. Cc l rng, khe nt nh hng rt ln n gi tr ca trng lng th tch ca ,nhngslngcckhent,mtntnlidoiukinthnhtoquyt 42.C hc nh. cng nhiu l rng, khe nt th trng lng th tch ca n cng nh. V vy magma thng c trng lng th tch ln hn trm tch (do trong chng t l rng) v vi c thnh to t khong vt calcit, c trng lng th tch t 15 25kN/m3, trong khi bn thn calcit c trng lng th tch ti 27kN/m3. Trong cng mt loi t l rng nh magma th thnh phn khong vt li ng vai tr quyt nh hn: Cng di su, t l thch anh cng gim th trng lng th tch ca li cng tng. Trong thc t, ngoi trng lng th tch ca trng thi t nhin, m ngi tathnggittltrnglngthtch,khiul,xcnhbngcccngthc (1.13), (1.14) nh ni trn, ngi ta cn dng mt s trng lng th tch khc tu theo trng thi ca : -Trnglngthtchtrngthikhtuyti(cngcgiltrng lngthtchkh,trnglngthtchct)xcnhsaukhi sykhmunhit1055oCtitrnglngkhngi.Trng lng th tch kh thng k hiu l c v c tnh theo cng thc: c=VQs (1.15) -Trng lng th tch ca trng thi no nc (bo ho nc) c c khinclpycclrngvkhent,thngkhiulnnhaybh c tnh theo cng thc: nn=V' Q Qn s + (1.16) trong : Qnl trng lng nc lp y cc l rng v khe nt ca mu . -Trnglngthtchtrngthiynicxcnhkhimuchm trong nc, thng k hiu l n v c tnh theo cng thc: n=V. V Qn s s (1.17) trong : nl trng lng ring ca nc. Trong cc ch tiu trn th trng lng th tch ca thng c s dng khi tnhtontrnglngcahayplccatrongcccngtrnhngmTrong mt chng mc no ,trng lng th tch cng c th c trngcho cht ca . Tr s ca trng lng th tch ca cnggn vi tr s ca trng lng ring thchngtchtcacngln,nghalrngcacngnh.Cngnh trng lng ring, cc gi tr ca trng lng th tch thng c suy ra t cc gi tr ca khi lng th tch ca xc nh trong nhng iu kin khc nhau. TheoR.A.Daly,N.A.Xhtovich,I.A.TurchaninovvR.V.Medvedevth trng lng th tch ca mt s loi c th ly theo bng 1.3. Bng 1.3 C hc .43 Trng lng th tch, kN/m3 Tn Khong dao ngTrung bnh Granit Syenit Bazan iabas Gabro Pyroxenit Peridotit unit St kt Ct kt vi hoa Gneis 25,2 28,1 26,0 29,5 27,4 32,1 27,3 31,2 28,5 31,2 31,0 33,2 31,5 32,8 32,0 33,1 23,5 26,4 25,9 27,2 26,8 28,4 26,9 28,7 26,9 28,7 26,6 27,5 29,0 29,5 29,9 32,3 32,3 32,8 24,6 26,5 27,3 27,8 27,8 44.C hc Khi lng th tch ca l khi lng mt n v th tch ca n m t nhin hay xc nh no . V tr s, khi lng th tch c tnh bng t s gia khilngcamu(baogmcncvkhtrongcclrng)vtonbth tch ca n (k c cc l rng v khe nt). Khilng th tch ca thng c k hiu l , n v tnh l g/cm3 hay t/m3: =Vm m mk n s+ + ;(1.18) trong :mnl khi lng ca nc c trong mu . mkl khi lng kh c trong mu . Nubquakhilngcakhvcoikhilngtonbmulmthkhi lng th tch ca mu s c tnh: =Vm

Vm mn s=+ (1.19) Khilngthtchnycacxcnhtrngthitnhinnnlra phi gi l khi lng th tch t nhin ca , nhng thc t thng gi tt l khi lng th tch ca . Cng ging nh trng lng th tch, khi lng th tch ca cn c xc nhtrongcciukinkhcnhauvtngngvichng,scnhngtngi khc nhau: -Khi lng th tch kh: c=Vms(1.20) -Khi lng th tch trng thi no nc (bo ho): nn=Vm m'n s +(1.21) -Khi lng th tch y ni:n=V. V mn s s (1.22) Trong cc cng thc trn: m l khi lng nc lp y cc l rng v khe nt ca . cncckhiukhccnghatngtnhnutrongcc cng thc trc . Gia cc khi lng th tch v trng lng th tch cng mt trng thi u lin h vi nhau theo mt quan h tng qut: = . g(1.23) V vy sau khi xc nh c khi lng th tch mt trng thi no s d dng tnh c trng lng th tch ca . C hc .45 xcnhkhilngthtch,cthdngnhiuphngphpkhcnhau, nhng ni chung, chng ch khc nhau v cch xc nh th tch mu . -Phng php cn o trc tip Phng php ny c s dng khi tnh cht ca cho php c th ct gt n thnhnhngmucdnghnhhcnhtnhnhhnhhp,hnhlpphng,hnh tr o kch thc mu s tnh c th tch ca n. Cn trc tip mu , s tnh c khi lng mu. T s suy ra c khi lng th tch mu . Phngphpnytcsdngrngrivvicgiacngmuthnhdng hnhhcquichunrtkhkhnvnhiukhikhngththchinc.Mtkhc, chnh xc ca cc kch thc hnh hc ca mu cng rt kh bo m. Ngi ta ch dng phng php ny nhng khong sn mui, kch thc mu ln, s sai lch khi cn, o khng nh hng lm n gi tr khi lng th tch ca . -Phng php dng ct v cn PhngphpnydoN.P.Gvozevadngtnm1948vrtcktqu.N c th xc nh c khi lng th tch ca c hnh dng bt k. Cch xc nh nh sau: Lyctthchanhemsngquaryc100l/cm2.Nungnng,nguiri rc vo bnh ng ct. Khi mt ct tht phng, ghi gi tr th tch ct V1. Mu c hnh dng bt k, khi lng t 0,2 1kg. em cn trn cn phn tch, c khi lng m. n mu vo trong ct sao cho mu chm hn trong ct. Lc bnh mt ct tr li bng phng, tng ng s c c mc th tch ct V2. Khi lng th tch ca s c xc nh theo cng thc: 1 2V Vm

Vm

= = (1.24) Lm vi ln, sau ly tr s trung bnh s hc ca chng, s c gi tr trung bnh ca khi lng th tch. Phng php ny khng p dng c vi cc nt n mnh. -Phng php bnh o th tch hay phng php bc parafin. Bnhothtchlmthnhtrbngkimloicngknhtrong150mm, cao 350mm. chiu cao 250mm c hn mt ng thc th bng ng, ng knh 8 10mm. Bnh o cha y nc ct v khi mc nc trong bnh cao hn l thot th nc s chy ra ngoi theo ng bng ng. Cch xc nh khi lng th tch bng phng php ny nh sau: Ly mu khong 0,2 1kg em cn bng cn phn tch, c khi lng m. 46.C hc Nu mu cht, cc khe nt, l rng nh th em bo ho s b mu bng nc c nhit trong phng hay nc si. Numuccckhentlnthphiphquanhmumtlpparafin sch,mng1mmbngcchchomuvoparafinnngchy(>5760oC) trongkhong12.Lyranguitrongkhngkh,khitrnmtparafincbt kh th phi ly kim h nng, chc thng l ra v mit phng li. Nuccmuckhentrtlnthkhngnnnhngngaymuvo parafinnngchy,trnhparafinthmsuvokhentlmsailchktquth nghim,trckhinhngparafin,nnbcchtmubnggiyhaytthn,theo F.A. Petrachkov nn ph mt lp parafin do, mm. Cn mu ph parafin, c khi lng m1. Buc mu ph parafin hay mu bo ho nc bng si ch mnh v th vo bnh o th tch y nc. Do chim ch, nc s trn ra qua ng bng ng xung ng o th tch hng di, cho ti khi mc nc trong bnh o ngang mc l thot. Cnngocchanc,ritrikhilngngo,vtrsychnh bng th tch ca mu c ph parafin l khi lng m2. Nu k n khi lng th tch ca cht lng (c th khng phi l nc ct), th khi lng th tch mu c th c xc nh theo cng thc: ( ) m m m .. . m

m m mm1 cl 2 pp clp1cl2 == (1.25) trong :m l khi lng mu th nghim. m1 l khi lng mu c ph parafin. m2 l khi lng cht lng chy ra t l thot ca bnh o. cl l khi lng th tch ca cht lng ng trong bnh o. plkhilngthtchcaparafin,lytrungbnhl0,9g/cm3 (dao ng trong khong 0,87 0,93g/cm3). Vimukhngphibcparafin,khilngthtchcansctnh theo cng thc: 2mm= (1.26) Khi lng th tch mu s c tnh bng tr s trung bnh s hc gia hai ln o s sai khc gia chng khng c qu 0,02g/cm3. -Phng php cn thu tnh Phng php cn thu tnh da trn c s nh lut Archimde: Mt vt nhng trong cht nc s b nc y t di ln trn vi sc y bng trng lng ca th tch nc b vt chim ch. C hc .47 Nh vy, khi tm c sc y ca nc s xc nh c th tch ca vt khi bitkhilngthtchcanc.xcnhscycancngitadng cn thu tnh (hnh 1.18). Cn thu tnh khc vi cn k thut l mt bn a cn treo rt cao so vi bn kia. Di y ca bn a treo cao c gn mc treo si ch buc khi cn trong nc,chphimnhvdo.Chiudichphitnhthnokhitreo,muhon tonngptrongncnhngkhngcchmvoybnh.Cchcncngtin hnh nh khi cn bng cn thng. Cchxcnhkhilngth tchbngcnthutnhtinhnhnh sau: Buc mu bng si ch mnh, do, sao cho khi mu ngp trong nc, s khng chm vo y bnh. Cnmucbucchtrong khng kh c khilng m. Ginguynacchaccqu cn,thmuvotrongbnhcha chtlng(nccthaydulatu theotnhchtcamu).Docsc y Archimde, cn cn s lch i. lm thng bng c th bng 2 cch: B bt mt t qu cn trong a i hoc thm vo bn a treocao, mt tqu cn khc. Khi lngcc qu cn bt i hay thm vo chnh l sc y ca nc, c biu din di dng khi lng, k hiu l m1. Chiakhilngchokhilngthtchcachtlng,scthtchca mu . Khi lng th tch mu s c xc nh theo cng thc: cl1cl1.mm

mm == (1.27) trong :m l khi lng mu cn trong khng kh. m1 l khi lng mu cn trong nc. cl l khi lng th tch cht lng. Khidngphngphpcnthutnh,mucngvncthcbc parafin. Khi y, cch lm v cng thc tnh ton cng s tng t nh phng php bc parafin nhng mu s s hi khc mt t. ( ) ( ) m m m m. . m1 cl 2 1 pp cl = (1.28) trong :m l khi lng mu trong khng kh. m1 l khi lng mu c ph parafin trong khng kh. m2 l khi lng mu c ph parafin cn trong nc. Hnh 1.18 Cn thu tnh 48.C hc Cc k hiu khc c ngha tng t nh trong cc cng thc trn. Ngy nay, xc nh nhanh hn, ngi ta c th dng cn t ng, trong cc gi tr ca khi lng mu trong khng kh hay trong cn thu tnh u c tnghinshaydngcctiaphngxgammaphtratmtngunphngx, quamu,timydbcx.Sphthucgiakhilngthtchcamu vi cng bc x qua mu, tnh phng x ca ngun s th hin trn biu c trng, qua s xc nh c khi lng th tch ca mu . Khi lng th tchcamu khi th nghim thng c tnh bngg/cm3. Do trong t nhin, mt vt c khi lng l 1g th cng s c trng lng l 1G, nn khi ni khi lng th tch ca vt l 1,7g/cm3 th cng c th ni c ngay l trng lng th tch ca n l 1,7G/cm3. Nhng do ngy nay, ngi ta khng tnh lc bng G hay kG m tnh bng N v cc bi s ca n (theo h thng n v quc t SI) v nulychngitrcagiatcritdobng10m/s2thcthcoi1kG=10Nv 1G/cm3 = 10kN/m3. Nh vy, t khi lng th tch xc nh c l 1,7g/cm3 s suy ratrnglngthtchcanl17kN/m3(cnnucnchnhxc,khilyg= 9,81m/s2 th trng lng th tch trong th d trn s ch l 16,68kN/m3). 1.2.1.3. rng v h s rng rng Trongbtkloinocnguclrngvkhent.Cclrngnyc th c hnh thnh trong qu trnh thnh to (cc l rng, khe nt nguyn sinh) haychnhthnhdoktqucaccqutrnhbincht,tikttinhkhcnhau (cc l rng, khe nt th sinh). Kch thc ca cc l rng, khe nt trong thay i rt ln: t nhng khe nt maodncchiurng 30% i vi cc loi , rng ca n thay i trong mt phm vi kh rng. Theo V.N. Kobranova (1957), rng ca mt s loi trm tch c th > 35% nh vi vi, lmit, ti 40% nh vi ct kt, bt kt hay ti 75% nh vi st kt, trong khi vi mt s loi magma nh granit, rng ch < 1% hay vi quarzit ( bin cht), rng cng ch khong 1%. xc nh rng ca , ngi ta c th xut pht t nh ngha ca n, lin hvimtschtiuxcnhcnhtrnglngthtchkh,trnglng ring ca , s tnh c rng, theo cng thc: sc - 1 n=(1.30) Khi xc nh rng h, ngi ta c th dng phng php P.Preobrazhenxki: em bo ho mu trong nc si hay du la. Theo s chnh lch khi lng mu trc v sau khi bo ho s xc nh c th tch cc l rng h. Th tch mu th c cc nh bng phng php cn thu tnh. Thctthnglymucthtchkhong100cm3,lauschbibnri em sy nhit 105 110oC, cho ti khi cn c khi lng khng i m. em bo ho nc bng nc si (khi mu khng chu tc ng ca nc) hay bng du la (khi mu b ho tan trong nc). mu c hon ton bo ho, phi 50.C hc t cc cha nc hay du la c mu trong vo bnh chn khng khong 0,5 1h.Saukhiboho,emcnmutrncnthutnh,ckhilngm1.Ly mu ra khi cn, lau kh mu v em cn trong khng kh, c khi lng m2. rng h ca mu s c xc nh theo cng thc: 100% .m mm m n1 22h=(1.31) H s rng Hsrngltsgiathtchcclrngvkhenttrongvthtch phn cng ca n. H s rng thng k hiu l e v tnh bng s thp phn. srVV e= (1.32) xc nh h s rng, ngi ta c th tnh ton theo cc cng thc lin h vi rng hay vi trng lng ring v trng lng th tch khca : n - 1n e=(1.33) v: 1 - ecs=(1.34) 1.2.1.4. Mt s ch tiu lin quan n pha lng ca Trongcc khe nt v l rngca thng cha nc.Lng nc nyph thuc vo iu kin thnh to . magma hay bin cht c thnh to trong iu kin nhit cao, p sut ln nn thng cha rt t nc (ch khong 1%). Cc trm tch cha nc nhiu hn v lng nc trong ph thuc vo ln ca ht v cht ca . c trng cho s c mt ca nc trong , ngi ta a ra mt s ch tiu sau: m ca l t s gia trng lng (khi lng) ca nc cha trong v trng lng (khi lng) ca mu kh tuyt i. m ca thng c k hiu l W, tnh bng %: 100% .QQ Wsn=(1.35) xcnhmca,ngitalykhong35vin,khilng> 200g.Chischbitrnmuvemcnvichnhxcn0,01g;ckhi lng m1. emsykhnhit105110oCchotikhilngkhngi.tmu vobnhhtm,nguiricnmusykh,chnhxcti0,01g,ckhi lng m. m ca s c tnh theo cng thc: 100% .mm m W1 =(1.36) C hc .51 Trscamsctnhtheotrstrungbnhshccaccmuth nghim. ht m ca l t s gia lng nc m c th ht v gi li trong cc l rng v khe nt ca n iu kin kh quyn bnh thng v trng lng mu kh tuyt i. ht m ca thng k hiu l Wh , cng c tnh bng %. 100% .QQ Wshh=(1.37) trong : Qh l lng nc m c th ht c v gi li trong n. xc nh ht m, ngi ta ly khong 3 5 vin , khi lng > 200g. Chi sch bi trn mu v em sy kh nhit 105 110oC ti khi lng khng i. t vo bnh ht m, ngui ri cn mu sy kh chnh xc ti 0,01g, c khi lng m. t mu vo khay, cho nc ngp ti 1/3 chiu cao mu th nghim. Sau 24h, cho nc ngp n 2/3 chiu cao mu v sau 24h na, cho nc ngp ton b mu. Chiu cao mt nc khng qu 2cm so vi chiu cao mt trn ca mu. Ngm mu ti khi t c khi lng khng i. Lau kh, cn mu chnh xc ti 0,01g, c khi lng mh. ht m ca s c tnh theo cng thc: 100% .mm m Whh=(1.38) ht m bo ho ca l t s gia lng nc m c th ht v gi li trong cc l rng v khe nt ca n iu kin chn khng hay di mt p lc no v trng lng ca mu kh tuyt i. Trong chn khng hay di mt p lc no , cc l rng v khe nt hu nh c lp y nc mu trng thi bo ho hon ton. Ch tiu ny, trong cc ti liu c, cng gi l m ton phn. ht m bo ho c k hiu l Wbh v cng tnh bng %. 100% .QQ Wsbhbh=(1.39) trong : Qbh l lng nc lp y cc l rng, khe nt. xc nh ht m bo ho ca , ngi ta c th dng phng php chn khng hay phng php un si. Trongphngphpchnkhng,mucsykh105110oCtikhi lngkhngi,tvobnhhtm,nguiriemcnchnhxcti0,01g, c khi lng m. Cho mu vo bnh chn khng, m my ht chn khng cho ti khi p sut ct thu ngn ch cn 4 5mm trong 14h. Cho nc vo ngp mu v tip tc m my chnkhngkhong12hnachotikhimtngoicamukhngcnbtkh. Cho khng kh lt vo bnh, sau 24h, ly mu ra, lau kh mt ngoi v cn chnh xc ti 0,01g, c khi lng mbh. 52.C hc Trong phng php un si, sau khi sy kh mu v em cn, t mu vo ni, nc ngp n 0,9 chiu cao ca mu v giyn nh vy sau 24h, nc ngp mu v un si trong 4h ri ngui. Sau 24h, ly mu ra, lau sch mt ngoi v cn chnh xc ti 0,01g, c khi lng mbh. ht m bo ho ca c tnh theo cng thc: 100% .mm m Wbhbh=(1.40) Ngoiccchtiutrn,cngcnphnbitchngvimtschtiuikhi cng c dng khi nghin cu l bo ho. bo ho ca c xc nh bng t s gia th tch nc c trong cc l rng v khe nt v chnh th tch ca chng. rnrVV S =(1.41) trong :Sr l bo ho ca . Vn l th tch nc c trong cc l rng v khe nt. trng thi bo ho hon ton, Sr = 1. bo ho thng c xc nh mt cch gin tip qua cc cng thc xc lp quan h gia cc ch tiu vi nhau. Th d: bhrWW S =(1.42) hay nn) - W(1 Sr=(1.43) m lm gim bn ca . Thc nghim thy l khi b no nc, bn nn mt trc ca gim i t 1,45 3,05 ln so vi mu trng thi kh gi. Nht l vi cc yu nh bt kt, st kt th vic gim ny li cng mnh. m lm tng trng lng th tch, bin dng v tnh dn in ca , nn khi tnh ton,thitkcngtrnhphitnhnsthayicakhichunhhngca nc. Theo Grisvan, tr s m ca mt vi loi c th thy trong bng 1.4. Bng 1.4 Tn m W, % ht m bo ho Wbh , % Granit Bazan 0,74 0,27 1,31 0,39 C hc .53 vi cht vi xp Ct kt 0,74 5,39 7,01 0,92 10,70 11,99 1.2.1.5.Quan h gia cc ch tiu c trng cho hm lng cc pha trong Giaccchtiunutrnctrngchohmlngccphatrongc nhngmiquanhcthitlpquacccngthclinhgiachng.Bng phngphpbinitonhcngintnhngcngthctheonhnghaban u,ngitachngminhcrtnhiucngthcthhinsphthucln nhau gia cc ch tiu nu trn. V vy, da vo mt vi ch tiu xc nh c, ngi ta c th tnh ra c cc ch tiu khc theo cc cng thc . Ngoicccngthcnutrn,trongccbitonchc,ngitacn thng s dng mt s cng thc, c tm tt trong bng 1.5. Bng 1.5 = s (1 n) (1 + W) = s (1 n) + nSr n

c = W 1+ c = e 1s+ n = (1 n) (s n ) n = nn n

nn = (1 n) s + nn

nn = n e 1e++ n = e 1e+ Sr = eW Sr = nc. nW . 1.2.2. TNH CHT C HC Tnh cht c hc l mt loi tnh cht vt l, xut hin trong cc qu trnh c hc do t nhin hay cu to bn trong ca gy ra, c trng cho kh nng chng li s bin dng v ph hu di tc dng ca cc loi ngoi lc. 54.C hc Tnh cht c hc ca c th hin qua cc ch tiu tnh cht c hc. Chng l cc thng s ca cc cc m hnh c hc c bn khc nhau. Tu theo dng ca m hnhmngitachiathnhccnhmchtiuctrngchobn,chotnhcht bin dng, cho tnh cht lu bin, cho tnh cht ng lc hay cng ngh Tnh cht c hc ca c th c nghin cu bng phng php th nghim iukintnhin,thnghimtrnmhnhhaytnhtonbngccphngphp gii tch. Phng php u tin ng tin cy hn c nhng khng phi lc no cng thc hin c. Phng php th hai km tin cy nhng d lm hn, n da trn c s l thuyt tng t v m hnh trong c hc v c p dng rng ri khi nghin cu trong phng th nghim. Phng php cui cng km chnh xc nht nhng cng li d lm nht.. 1.2.2.1. bn bncalkhnngchnglisphhucanditcdngca ngoi lc. Sphhulhintngxyrakhibindnglmphvccmilinkt trong vt, vt b chia lm hai hay nhiu mnh. Ngi ta chia ra: Phhuginxyrakhivtbphhudotcdngcangoilcmkhng thy c bin dng do. dng ph hu ny, nng lng b mt mt t nht v tc ph hu gn bng tc m thanh. Ko t l dng ph hu xy ra khi c s gim tit din mu ti kch thc b nht ri mu b t. Ph hu do l dng ph hu trung gian ca hai dng ph hu trn vi c im l bin dng do rt ln, thy r trn mt ph hu. bn ca c c trng bng tr s ng sut gii hn sinh ra ti tit din nguy him ca n khi b ph hu bng tc dng ca cc loi ngoi lc khc nhau. Tu theo dng ngoi lc m ngi ta c th xc nh bn khi nn, khi ko, khi ct, khi un trong cc trng thi ng sut n gin hay bn khi nn 3 trc trong trng thi ng sut th tch. Mt s c im v bn ca - bn ca ph thuc vo nhiu yu t. C rt nhiu yu t ph thuc vo bn ca , nhng ni chung c th chia lm 2 nhm: + Nhm cc yu t v bn cht. Trong nhm ny phi k n thnh phn khong vt, cc c im v kin trc v cu to ca , tnh khng ng nht, tnh d hng, tnh cht nt n, m ca +Nhmccyutlinquannkthutcngnghxcnh bn ca nh tnh nng ca cc thit b th nghim, iu kin tip xc gia mu v tmmcamy,cchthctngtivtctngti,cccchgiacngdngv mt mu th nghim Do chu nh hng ca nhiu yu t khc nhau nn khi xc nh bn, ngi talunmongmunchunhomu,thitbviukinthnghim.iugii thchchoccquynhnghimngtkhixcnhbnsaunycngnhvic C hc .55 phn tn ca cc kt qu th nghim xc nh bn ca bng cc phng php khc nhau. -S sai khc gia bn l thuyt v bn thc t ca : bnlthuytlbncaslinktgiaccphncbnnmtrong mng tinh th l tng. G.X. Zhanov tnh ton bn l thuyt ca tinh th mui n NaCl da trn c s xc nh lc F tc dng ph hu mng tinh th. Trong mng, mt yu nht l mt m hai bn ca n c cc ion i du lin tip. Lc F s phi thng c lc hp dn tng h gia cc ion nm gn nhau nht hai bn mt c th b ko t. Theo nh lut tnh in, lc ht ca cc ion c th xc nh theo cng thc: 22re F= (1.44) trong :eltrsintchbng4,8.10-8CGSE(tnhtronghCGS)hay bng 1,6 . 10-9C (trong h SI). rlkhongcchgiaccionmvdnggnnhaunhttrong mng tinh th NaCl v bng 2,8.10-8cm. Trong din tch 1cm2 ca mt mng tinh th, s cp ion s l: 2r1 N = (1.45) V vy bn l thuyt ca mng tinh th s l: P = NF = 42222re

rexr1= (1.46) Thayccgitrcaevrnutrnvocngthc(1.46)scP= 30.000MPa, mt gi tr m trong thc t khng th no t ti c. Khixcnhbnthctcatinhthmuin,gitrthucrtnh, thng ch bng 1/6000cagi tr bn l thuyt.L.A. Sreyner th nghim v thy l s sai khc gia bn l thuyt v bn thc t ca thp l 4.500 ln, ca thic l 2.000 ln, ca thch anh l 90 ln. gii thch s sai khc qu ln gia bn l thuyt v bn thc t, ngi tachorngtrongcctinhthkhngcshonhovcutonghalc nhng khuyt tt. Theo R. Thompson, th nhng khuyt tt ny c th l: +Daongnhit:nhitthng,ccphntntmngdaong khng iu ho vi bin bng khong 5 10% khong cch gia cc nguyn t. Dovy,ccphntcmtngnngnhtnh.Nhitcngcao,sdaong cng tng v ng nng cng ln. ng nng ny cng vi th nng do s tng tc 56.C hc gia cc phn t s lm tng khong cch cn bng gia chng, mng b n ra v khi ln c th ph hu mng tinh th. + Khuyt tt ti mt im: Loi khuyt tt ny c th l do thiu nt trong mng tinh th, hay s dch chuyn ca cc ion, nguyn t lm nt lch khi v tr cn ibanu,haycnhngntlvikchthclnhnhocnhhnkchthc nguyn t hay ion cc nt khc. Cc khuyt tt ny lm mo mng v yu mng tng im. + Khuyt tt theo mt ng: Loi khuyt tt ny do nhiu im khuyt tt lin tip hp thnh. Dng n gin nht l bin dng mp mng to thnh g x x hay mng b xon do cc lp trong mng b trt. + Khuyt tt b mt: Nhiu ng khuyt tt s to thnh khuyt tt b mt. Mt vt rn c th coi nh mt khuyt tt ca cu trc tinh th v cc ht nm trn vt rn c trng thi nng lng khc vi nhng ht nm bn trong vt rn. Khuyt tt b mt lm gim bn ca vt rn rt nhiu. Hnh 1.19.Cc loi khuyt tt timt im. a) Thiu nt;b) Lch nt;c) C nt l. Trong 1cm2 ca cu to tinh th, s lng khuyt tt l khong 102 1012. iu ny cng gii thch r s sai khc qu nhiu gia bn l thuyt v bn thc t ca vt rn. -Hiu ng t l Khithnghimbncaccmucngmtloi,cngmtdngmu nhng kch thc khc nhau th cc kt qu thu c cng khng nh nhau. S ph thuc ca bn ca cc mu cng mt loi c cng mt dng hnh hc vo kch thc khc nhau ca chng gi l hiu ng t l. Ni chung, thc nghim chng t l khi kch thc mu cng ln th bn ca n cng gim. Nhng kt qu th nghim ca E.I. Ilnixhkaja (1962), J. Bernaix (1967), E. Hoek v E. Brown (1980) chng minh iu v s ph thuc gia bncaccmuckchthckhcnhaucthhinbngcccngthc thc nghim, nh ca J. Bermaix: nooLL||

\|= (1.47) a) b) c) a) b) c) C hc .57 trong : lbncamuckchthcctrng(ngknhchng hn) l L. ol bn ca mu c kch thc c trng l Lo. nl ch s m, thay i t 0,1 0,5 ph thuc vo tnh cht nt n ca . J.Bernaixlmthnghimvinhiuloivktqucthhintrn hnh 1.20. Hnh 1.20. S ph thuc ca bn cc loi vo kch thc mu. 1. gneis cha biotit (n= 0,12); 7. St bn trung bnh (n=0,25). 2. vi (n = 0,12) ;8. gneis (n = 0,56) ; 3. gneis (n = 0,34) ;9. St kh gin (n = 0,457) ; 4. nt n (n = 0,27) ;10. B tng (n = 0,1) ; 5. nt n (n = 0,52) ;11. hoa (n = 0,07) ; 6. Ct kt phn lp (n = 3);12. Thch cao (n = 0,12). E. Hoek v E. Brown cng a ra cng thc kinh nghim c dng tng t nh cng thc ca J. Bernaix, nhng ch s m l 0,18. L.A. Sreyner a ra cng thc: n'n

la + = (1.48) trong :nl bn nn ca mu c kch thc l. al hng s. n lbnnncamuckchthctngiln,cthb qua hiu ng t l. 12312334685791011 12- 0,50 0.5 1 1.5 lgL, cmlg .kg / cm2lg, kG/cm2 58.C hc Ngi ta gii thch hin tng hiu ng t l bng l thuyt thng k hay l thuyt nng lng: bn ca vt rn (trong c ) l bn ca phn yu nht, ngha l ca cc phn khuyt tt trong vt. Kch thc mu cng ln th xc sut xut hincckhuytttcngnhiu.Vvy,viccmukchthcln,bncan thng nh hn so vi cc mu c kch thc nh. Tuy nhin, trong thc t i khi cng c trnghp khi tng kch thcmu thnghimthbncachngcngtngtheo.HintngnycM.I. Koyfman gii thch l do s ph hu lp b mt khi gia cng mu. Khi ch to mu th nghim thng lm ph hu lp mt ngoi ca mu. Kch thc mu cng ln thvng b ph hu b mttrong ton b mucngnh v do vy, bn ca mu s caohnbncamukchthcbmtrongbmtcamubphhurt nhiu. Cc l thuyt v bn: Vic nghin cu v bn ca vt liu (trong c ) thng c tin hnh trong cc iu kin tiu chun. Nhng trong thc t, di tc dng ca ngoi lc, vt liu lm vic v b ph hu mt trng thi ng sut hon ton khc, phc tp hn (nh trng hp chu tc dng ca cc ng sut chnh 1, 2 v 3 ). nhgi bn cavt rn trong cc trng thi ng sut phc tp bt k, ngi ta phi nu ra cc gi thuyt khc nhau gii thch nguyn nhn, c ch xut hin trng thi ng sut nguy him dn ti s ph hu vt liu. Khi trng thi nguy him, ng sut trong vt t ti gi tr gii hn. Qu gi tr ny, vt liu s b ph hu. Nhng gi thuyt nh vy c gi l cc l thuyt v bn v sau ny cng c coi l cc tiu chun bn ca vt rn c th hin di dng mt phng trnh biudiniukinphhuditcdngcaccngsutkhcnhau.Choti nay,cti20thuytbnkhcnhau.Diychnuramtsthuytbn thng c s dng trong tnh ton c hc . -Thuyt ng sut php ln nht y l l thuyt c in nht, c t thi L. De Vinci; G. Galilee (th k XVI) v sau ny c W. Rankine nu ra: Trng thi ng sut gii hn t c khi mt trong cc ng sut chnh t ti tr s gii hn; ngha l s ph hu vt do ng sut php ln nht gy ra: max=1[ ] (1.49) trong :1 = max l mt trong cc ng sut ln nht. [ ] l ng sut cho php ca vt liu. Trongtrnghpchuko,sbphhukhingsutchnhnhnht,v gi tr bng vi bn ko ca n: 3= k(1.50) Nhc im chnh ca thuyt ny l khng k n nh hng ca cc thnh phnngsutchnhkhctisphhu.Mtkhc,thuytnykhnggiithch c nhng kt qu th nghim thc t: mu b ph hu khi ng sut nh hn ng sutgiihnrtnhiukhinnmttrchaykhitrngthingsutthtch,ng sut ph hu mu li ln hn ng sut gii hn rt nhiu. C hc .59 Thuyt ny ch dng trong tnh ton bn ko ca vt liu gin. -Thuyt bin dng ln nht Thuyt ny do E. Mariotte nu ra t nm 1682, sau ny c Saint Venant pht trinthm,chorngsphhuvtliuldobindnglnnhttititdinnguy him. Trng thi gii hn t c khi bin dng chnh t ti tr s gii hn: gh 1 max = (1.51) trong :max = 1l bin dng chnh ln nht. ghl bin dng gii hn khi ko (nn) mt trc. Khi trng thi ng sut 3 trc, theo nh lut Hooke tng qut th c th vit: max= ( ) | || |E E13 2 1 + (1.52) hay 1 (2 + 3 )[ ](1.53) trong : 1 , 2 , 3 l cc ng sut chnh. l h s Poisson. Thuytnyknc3thnhphnngsutchnh.Tuynhin,ngoicc ng sut ny, bin dng gii hn cn ph thuc nhiu vo cc ng sut bn na, nn thuyt ny cng khng c s dng rng ri. -Thuyt ng sut tip ln nht Thuyt ny do C.A. de Coulomb ra t nm 1776, cho rng vt liu s b ph hu khi ng sut tip ln nht mt im no ca n t ti mt tr s gii hn gi l bn ct ca vt liu: max[ ](1.54) trong :maxlngsuttiplnnht,cthtnhtheogitrcaccng sut chnh 1 , 2 v 3- Nu 1 2 3th: ( )3 1 max 21 = (1.55) [ ] l ng sut tip cho php (gii hn bn ct cho php) ca vt liu. ||| |2 = (1.56) Do vy, cng thc (1.54) c th vit di dng: 1 - 32[ ](1.57) NavierphttrinlthuytcaCoulomb,chorngngsuttiptcdng trn mt trt t l vi ng sut php. Hin tng ph hu s xy ra khi ng sut tip tc dng trn mt ph hu t gi tr: =o+ (1.58) trong :o l bn ct (trt) ban u ca vt liu c trng cho lc lin kt ca n, sau ny thng k hiu l c. 60.C hc lhsmasttrong,ctnhtheogcmasttrongqua cng thc: =tg (1.59) v cng thc (1.58) s c vit di dng: = tg + c(1.58) Cc i lng v c th tnh theo cc gi tr ca ng sut chnh 1 v 3 , theo cc cng thc: = 2 sin 23 1 (1.60) + = 2 cos2 23 1 3 1 (1.61) trong : l gc gia hng ca 1 v hng trc x. Thay cc gi tr ca v vo cng thc (1.58), tm gi tr cc tiu ca o, ri p dng cho trng hp ph hu khi ko (1 = 0; 3 = k ) v khi nn (1 = n ; 3 = 0) s c phng trnh biu din l thuyt bn ca Coulomb Navier di dng: +=sin- 1sin1

kn (1.62) Th kim tra chnh xc ca l thuyt ny, theo cc kt qu xc nh bn nn v bn ko ca K. Szchy (1966) v I. Farmer (1968) vi quarzit th t s n / k bng t 15 72, trong khi gc ma st trong ln nht ca n l 60o. Thay gi tr ny vo cng thc (1.62) th t s tnh ton ch c l 13,9, ngha l cn khc rt nhiu so vi thc t. Sau ny Saint Venant, H. Tresca dng thuyt ny nghin cu vt liu do v tm thy s kh ph hp gia l thuyt v thc t. -Thuyt nng lng bin dng T nm 1856, C. Maxwell cho rng khi tc dng mt lc vo vt th, ngha l phi tiu hao mt nng lng lm bin dng n. V vy c th dnggi tr nng lng tiu hao bin dng vt liu lm ch tiu c trng cho bn ca nvngtachorngvtsbphhukhinnglngbindngttimtgii hn xc nh. Mi ti nm 1904, Hubert v sau l R. von Mises, H.Hencky nu thnh l thuyt: Trng thi gii hn ti mt im xy ra khi nng lng bin dng ring t ti gi tr tng ng vi nng lng ring khi ko t vt liu theo mt trc. Biu thc ton hc ca thuyt bn ny c th biu din: (1 - 2)2 + (1 - 3)2 + (2 - 3 )2=2 [ ]2 (1.63) Thuyt ny c dng kh rng ri, nht l vi cc vt liu gin. -Thuyt bn Mohr Nm 1900, xut pht t quan nim bn ca vt liu ti mt im c xc nh bng tr s ng sut ln nht v nh nht ti im , O. Mohr dng biu C hc .61 hnh hc c dng ng trn, c gi l vng trn Mohr, biu th trng thi ng sut ti mt im. Bn knh vng trn Mohr s ng vi tr s ng sut tip ln nht khi vt liu b ph hu. Theo O. Mohr, vt liu s b ph hu khi ng sut tip trong mt ph hu t ti mt gi tr xc nh, ph thuc vo ng sut php tc dng ln mt phng y hay khigitrlnnhtcangsutkochnhttigitrbnkocavtliu, ngha l: =f () (1.64) v3= k (1.65) trong : l tr s gii hn ca ng sut tip: =23 1 (1.66) l tr s ng sut trung bnh: =23 1 + (1.67) Sphthuc=f()cthcxcnhbngthcnghimtheomts trng thi ph hu khc nhau ca vt liu: Trng thi ko mt trc: 1 = 0; 3 = k ; Trng thi trt thun tu: 1 = 3 ; Trng thi nn mt trc: 1 = n ; 3 = 0; Trng thi nn hai trc vi 1 3. Trng hp ny ngi ta s biu din bng mt vng trn tm ti im c honh 23 1 + v bn knh bng 23 1 . Sauvngbaocaccvngtrntrnscnggiihnbnca vt liu, th hin quan h = f() (hnh 1.19). Mohr ngh phng trnh ca ng bao c dng: c2f23 1 3 1+ ||

\| + = (1.68) trong : c l hng s, v tr s bng gi tr ca ng sut ct (trt) khi ng sut php bng 0. Hngs ny cng thng c gi l cng lc lin kt (lc dnh). A 31tc// =

()fA3 c10PB2AB0 62.C hc a) b)c) Hnh 1.19. Thuyt bn Mohr. a) Quan h tuyn tnh = f();b) ng sut 2 khng nh hng ti bn nn 3 trc; c) Quan h phi tuyn tnh = f(). Nu coi gn ng l hm s f t l bc nht vi bin s 23 1 + theo mt h s t k k th phng trnh (1.68) s tr thnh: c2k 23 1 3 1+ + = (1.69) tm c v k, thay ccgi tr ca 1 v 3 caphng trnh trn trong trng thi ng sut nn v ko mt trc (1 =n ; 3 = 0 v 3 = k ; 1 = 0), s c: k nk n k + = (1.70) vk nk n. c + = (1.71) Thay tr li ccgi tr ca k v c va tm c vo phng trnh (1.69), bin i n gin, s c: n 3kn1. - = (1.72) Tsn/klicthxcnhbngcngthc(1.62)trongthuytbnca Coulomb Navier. Thay vo, s c: n 3 1.sin 1sin 1 - = + (1.73) ychnhlphngtrnhcangbaoMohr,biudintheoccngsut chnh ln nht v nh nht cng vi gc ma st trong ca vt liu. ngha vt l ca ng bao Mohr l khi mt trng thi ng sut bt k c xc nh bng vng trn Mohr m nm hon ton pha trong ng bao th vt liu s khng b ph hu. Nu vng trn tip xc vi ng bao th vt liu s b ph hu theo mt mt phng hp vi hng ca ng sut chnh ln nht mt gc . Thuyt bn Mohr khng nhng c trngcho trng thi ng sut khi ph hu vtliumcnthychngcamtphhu.Vtliusbphhukhing sut tip vt qu tr s gii hn c xc nh theo tung ca im m ng bao ct trc tung hay khi ng sut ko ln hn bn ko ca vt liu (khi ng sut tip bng 0) chnh l honh ca im m ng bao ct trc honh trn th = f(). Nhiutcginuradngcangbaolnhngngconghnhhc khcnhau:NcthgnnhparaboltheoG.N.Kuznexhov,gnnhlhyperbol theoI.N.Kaxhaurovhaynhngdnggnngkhc.Trongtrnghpngin C hc .63 nht, ngi ta coi dng ng bao l thng khi y phng trnh ca ng bao s c dng nh cng thc (1.69): c2k 22 1 3 1+ + = hay vit di dng cc ng sut tip v ng sut php: =k + c (1.74) Phng trnh ny cng ging nh cng thc (1.58) trong thuyt bn Coulomb Navier. V vy, c th coi thuyt bn Coulomb Navier l mt trng hp c bit cathuytbnMohrvngitacnggilthuytbnhayiukinbnMohr Coulomb. Thuyt bn Mohr khng k n thnh phn ng sut trunggian 2. Nhng thc t, trong trng hp ng sut th tch (c c 1, 2 v 3) th khi v vng trn Mohr, r rng l ng sut 2 khng nh hng ti tung ca im P khi vt trng thi gii hn (hnh 1.19b). ThuytbnMohrcsdngrngrivivtliugin.Trongchc, ngi ta thng s dng thuyt bn Mohr vi dng ng bao cong (hnh 1.19c). -Thuyt bn Griffith A. Griffith nghin cu s ph hu ca vt liu gin, trong c cc khe nt sp xp rt ngu nhin. Di tc dng ca ngoi lc, ti phn u mt cc khe nt xuthinhintngtptrungngsut,lmcckhentphttrinthmvcui cng vt liu b ph hu. Nm1924,datrnscnbnggiacngcangoilcthchinkhilm tng chiu di ca khe nt v cng tiu hao khi y to thnh b mt mi ca vt liu, Griffith tnh ton iu kin ph hu ca vt liu gin, c cc khe nt. Gi s c mt di vt liu n hi chiu dy l 1 n v, trong c mt khe nt hnh ellip m trc ln ca n vung gc vi hng tc dng ca lc ko. Ngi ta xc nh c ng sut ln nht ti mp ellip, theo cng thc ca C.E. Inglis (1913): max=2o c (1.75) trong : o l cng trung bnh ca ngoi lc. c l mt na chiu di ca khe nt ellip. l bn knh cong. Do ng sut max ny m khe nt pht trin thm. Griffith tnh s chnh lch nng lng ca di vt liu khi khng c v khi c khe nt ellip. S chnh lch ny cng chnh l nng lng cn thit to thnh khe nt ellip. Gi s chiu di ca di vt liu vn khng i sau khi to thnh khe nt ellip, th s chnh lch nng lng s l: 64.C hc Ec W2o2e =(1.76) trong : E l mun n hi ca vt liu. ng thi khi to thnh khe nt ellip, tc l to ra nhng b mt mi, nn nng lng b mt xut hin khi to thnh cc khe nt ellips l: Ws=4c.T (1.77) trong :T l sc cng b mt. y l mt ch tiu thng t c xc nh. Vi khong vt calcit, theo Tourenq v Denis th T = 0,23J/m2. Nh vy, khi to thnh khe nt ellip, nng lng b gim i l: W = We Ws= 4cT - cE2o2 (1.78) Khi trong di vt liu bt u xut hin khe nt, ngha l vt liu b ph hu v phng trnh nng lng (1.78) s t cc tr. o hm ca W v cho bng 0, s c: cET 22o= (1.79) C th coi rng khi xut hin khe nt th gi tr ca o bng vi gi tr ca k.Do vy: cET 22k= (1.80) y cng chnh l biu thc ca thuyt bn Griffith. Nhng nm 60 ca th k XX, nghin cu mt cch tng qut hn v chnh xc hn (khc phc vic xc nh nng lng b mt ca vt rn rt kh khn v km chnh xc), ngi ta ci bin l thuyt ca Griffith. utinlE.HoekvZ.T. Bieniawski nghin cu trng thi ngsutdivtliucchacc vikhenthnhellipc trccan hpvihngcangsutchnh mt gc (hnh 1.20). Phnvtliuxungquanh ellip,dostcngcaccng sut chnh s xut hin cc ng sut x , y v . Cc ng sut ny c th tnhtheoccngsutchnh(cng thc1.60v1.61).Ringthnh phnngsutydctheotrcln caellipnhhngkhngngk 3131xxyyxxyxyHnh 1.20. ng sut tc dng ln vt c l hnh ellip, nghing vi hng 1 mt gc . C hc .65 ti s tp trung ng sut u mt ellip nn c th b qua.ng sut sinh ra ti mt im mp khe nt hnh ellip c th tnh theo cc ng sut trn bng cng thc ca Inglis: = { x [ m (m + 2) cos2 sin2] xy [2(1+m2) sin cos]}(m2cos2 + sin2)1.(1.81) trong :lngsutchngtiptuynvikhentelliptimtim trn ellip. ml t s gia bn trc b v bn trc ln ca ellip. l gc hp gia on thng ni im ang xt trn ellip vi tm ca n v trc y. V khe nt mnh v ko di nn gi tr ca m rt nh. ng sut ko ln nht s ti mt im no u mt ca ellip, ngha l gc cng rt b. Khi tin ti 0 th c th coi nh sin v cos 1, ng thi b qua cc v cng b bc cao th cng thc (1.81) s c rt gn thnh: = 2(x . m xy . ) (m2 + 2 )-1 (1.82) xc nh cc cc tr ca ng sut, ly o hm ca biu thc trn theo , ri cho bng 0, s c: 2 xy (m2 + 2 ) 2(mx xy )2 = 0(1.83) Kt hp 2 phng trnh (1.83) v (1.82) s c: = xy (1.84) Thay gi tr ca va tnh c vo phng trnh (1.82). Gii phng trnh bc 2 ny theo 1/ , s tm c: | | m1 1xy2xy2x x + = (1.85) Thay gi tr ca 1/ vo phng trnh (1.84), s c: 2xy2x xm + = (1.86) y chnh l gi tr ln nht v nh nht ca ng sut ti im u mt ca ellip. Khi b ph hu trng thi ko mt trc th xy = 0 v x = k. Thay cc gi tr ny vo cng thc (1.86) s c iu kin pht sinh cc khe nt (b ph hu), s l: m=2x=2k(1.87) Thay gi tr ca m trong cng thc (1.87) vo cng thc (1.86), s c iu kin bn Griffith biu din theo cc ng sut thnh phn: 2xy2x x k2 + = (1.88) hay 2xy=4k (k x ) (1.89) 66.C hc Mun biu din iu kin bn Griffith theo cc ng sut chnh th li thay cc ngsutthnhphntrongcngthc(1.86)bngcccngthcnutrn(cng thc 1.60 v 1.61) s c mt biu thc tnh m theo cc gi tr ca 1 , 3 v gc : ( ) ( ) | | ( ) | |2123212321 3 1 3 12 cos212 cos21m)` + + + = (1.90) tm cc tr ca biu thc ny, ly o hm ca n theo v cho bng 0, s c: cos 2=( )3 13 12 + (1.91) Biu thc ny ch c ngha khi 1 + 33 0. Thay gi tr ca cos2 vo cng thc(1.90)vlydumcaphnsaucacngthc(dolygitrngsutnh nht) th s c: ( )3 123 14) (- m + = (1.92) T iu kin pht sinh khe nt (cng thc 1.87) v coi ng sut ko c gi tr m, nn: k2 m = (1.93) Kt hp 2 cng thc (1.92) v (1.93) s c: k3 123 18) ( = + , vi iu kin 1 + 33 0 ; (1.94) ychnh l iu kin ph hu ca Griffith, biu th theo cc ng sut chnh, trong trng hp ko mt trc. Nu coi 3 = 0 v1 =n , ngha l trng thi nn mt trc, thay vocng thc trn th n s bng 8 ln k. iu ny khng ph hp vi thc t, v i vi , t s ny thng t 10 50. Nm1962,F.A.McClintockvJ.B.Walshphttrinthmlthuytca Griffith: Khi nn, cc khe nt b khp li v trn mt ca chng xut hin lc ma st. Hin tng ph hu s xy ra khi: ( ) ( )ckck23212 1 4 1 1 + = + + + (1.95) trong :l h s ma st trn mt khe nt. C hc .67 cl ng sut theo hng vung gc vi mt khe nt, cn thit khp kn khe nt. Theo W. Brace, tr s ca c rt nh, c th b qua, nn cng thc trn s tr thnh: ( ) ( )k23214 1 1 = + + + (1.96) hay ( )k 3 1 3 124 ) ( 1 = + +(1.97) Khi trng thi nn mt trc th 1 = n v 3 = 0, thay vo cng thc trn s c t s: +=2kn14(1.98) Vi quarzit, cho rng gc ma st trong ln nht l 60o th = tg =3v khi y, t s n / k tnh theo cng thc (1.98) s bng 14,9. Mt gi tr c th chp nhn c.Ni chung, l thuyt ph hu ca A. Griffith v cc ci bin sau u dng gitrbnkocavtliuviukinbnthngcbiudintheocc ng parabol. Cch tnh ca Griffith khi k n ma st cng rt ging vi cch suy dincaCoulombNavierkhitmgitrcctiucao,nnA.R.Jumikischo rng, thuyt bn Griffith cng l mt trng hp c bit ca thuyt bn Coulomb. NhiunhnghincuchorngthuytbnGriffthtuynghincutrnvt liu gin, nhng s dng rt ph hp vi cc cng. Tuy nhin, phi lu ti cc yu t khc lm sai lch kt qu so vi l thuyt. -Thuyt bn Hoek Brown Nm1980,E.HoekvE.Brownnuraiukinphhutheotng quan gia cc ng sut di dng: 1= 3 +( )212n 3 ns m + (1.99) trong :1v3lngsutchnhlnnhtvnhnhttrongtrnghp nn ba trc. n l bn nn mt trc ca mu . m v s l nhng hng s t l vi gc ma st trong v cng lc lin kt. Cc hng s ny thay i tu theo tng loi : Vi m, c th bng 0,001 vi phong ho rt mnh hay bng 25 vi mu cng; vi s, hng s ny s bng 1 vi mu , cn trong khi , s < 1. Gi tr ca m v s c th thy trong bng 1.6 (theo E.Hoek, 1983). iu kin bn ca Hoek Brown cng c th vit di dng khc: 68.C hc 1= 3 +ns mn3+ (1.100) hay s mn3n3n1++= (1.101) Bng 1.6 Loi Carbonat St, bt kt, phin st Ct kt, quarzit Magma ht mn Magma ht th, bin cht Cht lng msmsmsmsms Mu 71101151171251 Khi cht lng tt khng phong ho 3,50,150,17,50,18,50,112,50,1 Khi cht lng tt phong ho nh 0,70,00410,0041,50,0041,70,0042,50,004 Khi cht lng trung bnh, phong ho va 0,140,00010,200,00010,300,00010,340,00010,50 0,0001 Khi cht lng km, phong ho mnh 0,04 0,00001 0,05 0,00001 0,08 0,00001 0,09 0,00001 0,13 0,00001 Khi cht lng km, phong ho rt mnh 0,007 0 0,010 00,0150 0,017 0 0,025 0 Vi cc mu , khi s = 1 th cng thc (1.100)s tr thnh: 1= 3 +n1 mn3+ (1.102) Nm1983,E.Hoekli nuracngthcbiudiniukinbn theong sut tip tc dng dc theo mt ph hu di dng: =(cotg i-cos i ) 8mn (1.103) trong : il gc ma st trong tc thi ti gi tr v cho. C hc .69 Nh vy, l thuyt ph hu ca Hoek Brown c th dng c cho c mu v khi vi cc mc phong ho khc nhau. -Thuyt bn Franklin Mitrngthingsutbtkucthmtbng3ngsutchnhvdo vy,cthbiudinbngmtimtronghtaccngsutchnh(hto Descartes). Tp hp tt c cc im tng ng vi trng thi ph hu th s c mt mt gi l mt bn c trng cho bn ca vt liu (hnh 1.21). Dng mt bn thng c xc nh bng thcnghim.Tnhngthnghimbn trng thi ng sut n gin (nh ko, nn mt trc)haytrngthingsutphctp (thnggpnhttrongccthnghim3trc vi123),ngitasvccc ng ng sut. Trn hnh 1.21, cc im A, B, C ng vi ccimphhudokhinnmttrc.Cc imD,E,Fsngviccimphhukhi ko mt trc. Khithnghimhaitrc,sccc ng cong ph hu AB, BC v AC; cn khi th nghim 3 trc i xng trc (mt cch gi khc ca s th nghim vi 1 2 = 3) th s cccngcongAG,BHvCItrnmt bn. nghin cu s ph hu, J. Franklin nghin cu 7 quan h khc nhau, c trng cho iu kin ph hu ca vt liu: 1 = A + B3 (1.104) 1 = A + BC3 (1.105) 1 = Alg (B + 3 ) (1.106) 1 3=A + B3C (1.107) 1 3=( )CB A3 13 1+ + + + (1.108) 1 3=A + B (1 + 3 )C (1.109) 1 3=A (1 + 3 )B (1.110) trong : A,B,Clnhngthngs,xcnhphhpviccngcong thc nghim.65 Trong cc quan h trn,Franklin cho rng phng trnh (1.110) m phng tt nht nhng thuc tnh c bn ca mt bn, nht l cho cc mu . Thng s A thay i trong khong 1 n 8. Thng s B l mt i lng khng th nguyn v thng thay i trong khong t 0,6 n 0,9. Hnh 1.21. Mt bn trongbiu ng sut 3 chiu. 70.C hc GiaAvBcngcthxclpcmtquanhtheophng trnh: B - 1nA =(1.111) Trong trng hp nn mt trc (1 = n v 3 = 0) th phng trnh (1.110) c th vit: Bn3 1n3 1

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\| + = (1.112) y chnh l iu kin bn do J. Franklin a ra s dng trong thc t. Tuy nhin, s tnh ton ch hn ch trong vng trng thi ng sut th tch. Cc thuyt bn trn c nghin cu trong cc iu kin kh l tng m thc tkhngphilcnocngthchinc.Mtkhc,phhuvtliulmtqu trnhphctpnncnphinghincu,honthinthmnhtlbngccphng phpthcnghim.Trongthcttnhton,clhplhncldngccthuyt bn ca O. Mohr, E. Hoek v J. Franklin (theo E. Gaziev, 1973). Cc phng php xc nh bn ca -nh gi s b bn ca Khi khng c nhng th nghim i hi phi c nhng thit b th nghim chnh xc, phi gia cng mu nghim ngt th n gin nht, ngi ta c th dng ba a cht, dao b ti xc nh mt cch s b bn ca . Vicgitnccloi,mcbnvngcachngvnhngduhiubn ngoi ca khi chu va p ca ba hay o gt bng dao so vi bn nn mt trccatnhbngMPatheoHiChcQuct(ISRM)cththytrong bng 1.7. Bng 1.7 Va chm vi ba a cht V vnD p v Gt bng dao D Kh p v, cn mt s ln p mnh Ch c th st m Cc yuRt yuYuBnRt bnCc bn mm cng 2 62060200 MPa - bn ca cc trng thi ng sut n gin bn ca khi ko,nn mt trc hay khi ct, un ccoi l bn cctrngthingsutnginnht.Ccktquthuctrongccdngth nghimnylnhngctrngcbncasdngtrongthitktnhton cng trnh. Tuy nhin, d l trng thi ng sut n gin nht th vt liu cng lun lun trng thi ng sut phc tp, trong c mt loi ng sut ng vai tr quyt nh.Vvy,khithnghim,cnphihnchnmcthpnhtccyutnh hng ti trng thi ng sut n gin ca . + bn nn mt trc C hc .71 bn nn mt trc l ch tiu thng c dng nht khi nh gi tnh cht c hc ca . V tr s, n c tnh bng t s gia lc nn ln nht lm ph hu mu Pmax v din tch tit din ngang ban u camu Fo: omaxnFP= (1.113) bn nn ca thay i trong mt phm vi rt rng, c th t 0 600MPa (V.V. Rzhevxki v G.Ya. Novik, 1973). Theo E.G. Gaziev (1973), tr s bn nn ca mt vi loi nh sau: Gneis: 81 327 MPaTuf : 3,5 52 MPa Granit: 37 379 MPaBazan: 150 350 MPa vi:6 360 MPaCt kt: 11 252 MPa Dochunhhngcanhiuyutkhcnhaunhnitrn,nnkhith nghimxcnhbnnn,ngitathngyucurtnghimngtvvicgia cng mu cng nh k thut th nghim: Mu c ch to t cc mu ly cc l khoan, cc cng trnh ngm hay cc khi c khai thc bng mi phng php (tr phng php n mn). Mu phi c to bng phng php khoan kh. Nu khng th phi c ghi ch r rng. Mu m phi c bc bng mt lp vt liu cch nc. Vi nhng c tnh d hng, nu c th, cn phi khoan ly mu theo 3 hng khc nhau. Mu thng c dng hnh tr. Mt mu phi c mi nhn. S sai lch v song song gia 2 mt mu v vung gc gia mt mu v ng sinh u khng c qu 0,05mm. x x ca mt mu khng c qu 0,03mm.Tsgiachiucaov ng knh mu th tutheo qui trnhthnghimcaccnc khcnhaumcthbng1 0,05(theotiuchuncaLin Xc)hay2(theotiuchun caccncphngTy).nh hngcatsnyntrs cabnnnmttrcca scnintrongphnsau. Hnh 1.22. Xc nh bn nn mt trc. 74.C hc Mu c t gia tm cc tm m ca my nn. Cc tm ny phi c mi nhn mt v mt trong hai tm phi c dng mt cu hay c b phn nh tm phn b u ti trng. Tc truyn p lc ca my nn phi t 0,5 1 MPa/s. Ti trng c tng dn ti khi ph hu mu (hnh 1.22). Rt nhiu tc gi nghin cu nh hng ca t s gia chiu cao v ng knh ca mu (h/d) ti tr s ca bn nn mt trc. Trn hnh 1.23 th hin s ph thuc gia bn tng i ca cc mu c t s (h/d) khc nhau. Mu c t s (h/d) = 2 c coi l 1 n v bn. 1. hoa 2. Argilit 3. Gch xy dng4. phn 5. Aleurolit 6. Ct kt Trongkhongts(h/d)=1,52,khits cngtngthbnnn cnggimmnh.bn canhngmuthptnglnldovngnhhngmastmtucbi trn, trong mu xut hin trng thi ng sut nn 3 trc, bn s ln hn khi nn 1 trc. Khi t s (h/d) 2, phn gia ca mu to thnh trng thi nn 1 trc v khi tng t l (h/d), th sc chng ph hu ca mu khng cn ph thuc vo ma st trn mt u na. Chiu cao mu cng tng, bn mu gim i do vic gim s n nh dc ca cc mu. Ts(h/d)ngvaitrquantrngkhixcnhccctrngvtlca: khi t s ny cng tng, mun n hi (E) v h s Poisson () gim cho ti khi t s (h/d) 2. t s ny, tr s mun n hi khng ph thuc vo iu kin mt mu. Bin dng t bin cng tng ln khi chiu cao mu tng v s n nh khi t s (h/d) 2. RtnhiutcginhR.K.Dhirvnhngngikhc(1972),B.T.Brady (1971), D.W. Hobbs (1964) u c nhng kt qu th nghim v kt lun l khi t s (h/d) 2 th cc kt qu thu c khi xc nh bn nn ng tin cy v n nh hn. H ngh nn ly t s (h/d) xp x bng 2 khi xc nh bn nn 1 trc ca . 35142660 1 211.5h/dHnh 1.23. S ph thuc ca bn nn 1 trc vo t s h/d. C hc .75 mt s nc nh M, Php, n qui nh t s(h/d) = 2 2,5 khi th nghim xc nh bn nn 1 trc ca . tnh ton bn nn mt trc theo kt qu th nghim ca mu c chiu cao khcnhau,ngitaathmvomtshshiuchnhvotrongcngthc tnh bn nn: 2 nd kP 4= (1.114) trong :Pl ti trng ph hu mu. dl ng knh ca mu hnh tr. klhshiuchnh,cthxcnhbngnhiucngthckinh nghim khc nhau:-Theo cc sch C hc ca Lin X c, k = 0,778 + 0,22(d/h). -Theo M.Zern, k =h / d 2 . -Theo G. Bausinger, k = 0,875 + 0,25 (d/h). -TheothngkcaVinnghincuachcMvTrcatonLin bang (VNIMI) Lin X c) th k = 0,754 + 0,496 (d/h). Theocngthcny,cthlpbnggitrktheots(h/d)nhtrongbng 1.8. Bng 1.8 T s h/dkT s h/dk 0,61,591,41,11 0,71,471,61,06 0,81,391,81,03 1,01,252,01,00 1,21,162,20,98 Trong cc c cc h mt yu nh mt phn lp, mt phn phin th