Chuong 8xong 7754

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CHNG 8: KHO ST A CHT CNG TRNH 8.1. Ni dung ca kho st a cht cng trnh +Lmrcciukinachtcakhuvcdkinxydngcng trnh+Doncchintngachtcthxyratrongqutrnhthi cng, khai thc s dng cng trnh. + xut cc bin php x l cc iu kin a cht cng trnh khng c li. hon thnh cc nhim v trn, ni dung kho st a cht cng trnh bao gm : + Thu thp v nghin cu tt c cc ti liu a cht cng trnh v cc ti liu c lin quan v khu vc d kin kho st,+Tinhnhkhostachtthcabaogm:ovbna chtcngtrnh,achtthuvn,amo-tnkinto...nhm gii quyt cc vn a cht nhanh chng. + T c s o v bn , tin hnh thm d gii quyt v nh tnh, nhlngnhngvnmtronggiaionovcntnti. + Tin hnh th nghim cc c tnh c-l ca t lm nn cng trnh, vt liu xy dng. + Nghin cu cc vn khc lm c s cho vic khc phc cc iu kin a cht khng thun li nh:+ Trong qu trnh khai thc, s dng cng trnh cn c th tin hnh cng tc quan trc chnh l cc ti liu a cht s dng trong qu trnh thit k, thi cng cng trnh. Kt qu cng tc kho st a cht cng trnh bt k giai on no cng phi c bo co kt qu bao gm : cc bn v (bn , mt ct a cht . .) cc s liu o thc t ti hin trng, cc kt qu th nghim ti phng , thuyt minh km theo. Kho st a cht cng trnh l mt cng tc khoa hc- k thut phc tp, do , cn phi tun theo cc nguyn l c bn sau : + Nguyn l k tha+ Nguyn l giai on+ Nguyn l kt hp trong kho st a cht cng trnh 8.2. Cc phng php kho st - o v bn a cht cng trnh. - Khoan o thm d. - o a vt l trong l khoan, trn b mt a hnh. - Th nghim trong phng trn cc mu chn. - Th nghim ngoi tri v a cht cng trnh v a cht thu vn 8.2.1.o v a cht cng trnh Nhc im ln nht ca cng tc o v bn a cht cng trnh l khng th quan st c cc lp t , cc hin tng a cht di su, nht l cc lp b che ph bi cc trm tch mm ri khc. Tuy nhin, y l cng tc kho st c tin hnh u tin, qua , ta c th nh gi s b c cc iu kin a cht cng trnh trong phm vi kho st8.2. 2.Cng tc khoan o thm d Cc cng trnh khoan o thm d bao gm ; h o thm d, h khoan thm d, ho thm d, hm thm d H o thm d thng c tit din hnh ch nht vi kch thc (1.5x2.5)m. Chiu su o thm d thng khng ln (thng thng nh hn 10m). i khi, chiu su h o thm d cng c th su hn, lc , phi c cc vt liu chng thnh h o (trng hp ny thng gi l ging o thm d). Ni chung, cc hnh thc o thm d c u im l quan st a tng, cc c im a cht trc quan, chnh xc nhng nhc im l tn nhiu nhn cng, su kho st khng ln, kh khn khi gp cc lp t cng chc, mc nc ngm nng. Cng tc khoan thm d c th khc phc c nhc im ni trn, su khoan thm d c th ln n hn 1000m. Thnh phn v cc tnh cht ca t c th c nghin cu qua vic ly mu t h khoan (nu khoan c ly mu) hoc i khi cng c th nghin cu thnh phn t thng qua cc vn v ca t (nu khoan ph hu). C hai nhm phng php khoan thm d : khoan tay v khoan my. Hin nay, c 3 phng php khoan ph bin trong kho st a cht cng trnh: khoan xoay, khoan p v khoan xoay p 8.2. 3. Thm d a vt l u im ca phng php ny l+C th nghin cu cc cu to a cht su ln (c khi ln n hn 1000m). + i khi mt loi tn hiu c pht i cng c th cho c nhiu loi thng tin nh : tnh cht ca t , mt ct a cht .. + Vic nghin cu a vt l theo ngha t bn thn ca n l nghin cu khi khng gian nn rt thch hp cho vic nghin cu tng quan a cht trong khu vc. + Cc kt qu o a vt l thng c ghi li bng thit b t ng nn tnh khch quan trong s liu rt cao. + Mt s thit b o a vt l rt gn nh, tnh c ng cao, nng sut lm vic tng i ln nn rt ph hp trong kho st a cht cng trnh. Nhc im ca phng php ny lKt qu o c th chu nh hng kt hp ca nhiu yu t, v d in tr ca t ph thuc vo nhiu yu t : rng, m, t trng, nhit . . nn rt kh phn bit yu t no c nh hng quyt nh n kt qu o, chnh v th, phng php a vt l trong kho st thng ch p dng khi bit c mi lin h gia yu t nh hng ch yu vi kt qu o. Phng php in: da trn c s cc loi t khc nhau hoc c m khc nhau s c in tr khc nhauPhng php chn ng : Kho st a cht cng trnh bng phng php chn ng da vo nguyn l nghin cu phng v vn tc truyn sng n hi pht sinh do va chm hay do n trong trong lp phn v Qu t8.3. Th nghim a cht cng trnh 8.3.1. Cng tc th nghim trong phng Vic tin hnh cc th nghim trong phng c u im l nhanh, d thc hin, t tn km, c th xc nh c nhiu ch tiu trong mt mu. Nhc im l trong mt s loi t , vic ly mu nh kh m bo tnh nguyn dng. Kt qu th nghim khng chnh xc so vi iu kin t nhin ca t . 8.3.1.1. Cc th nghim l hc v c hc ca t : Trong th nghim thuc cng tc kho st a cht cng trnh, i vi cc mu t, c th chia lm 2 dng th nghim : th nghim t nn v th nghim t s dng lm vt liu p. Ph bin nht l th nghim nn, th nghim ct, th nghim xuyn, th nghim m nn . . . v cc th nghim xc nh cc ch tiu chuyn mn khc. 8.3.1.2. Cc th nghim l hc, ho hc v sinh hc ca nc di t 8.3.2: Th nghim ngoi hin trng 8.3.2.1.Th nghim ht nc Cc ti liu th nghim c lp tp hp lp th Q = f(S), q=f(S) v tnh h s k. 8.3.2.2. Th nghim nc trong h o H s thm c xc nh s b theo cng thc Tuy nhin xc nh hn c th tnh theo cng thc sau: Q : lu lng nc (m3/ng) K : h s thm (m/ng) F : tit din vng kim loi kim loi trong (m3). (0,1m3) Hk : p lc mao dn hnh thnh do nc thm vo t, bng 0,5 chiu cao mao dn h : b dy lp nc trn mt t Z: chiu su thm FQK =( ) Z h H FQZKk+ +=8.3.2.3. Phng php nn tnh trong h o 1

3

Hnh 8.2: S th ngim nn tnh 1. Dm gnh2. Kch3. Cc neo4. Bn nn 4 2 Trn c s quan st ti trng nn v ln ca bn nn, ngi ta thnh lp th quan h ln bn nn v ti trng S = f(S).Gi tr mun bin dng E c xc nh theo cng thc sau Trong : E mun bin dng , kg/cm2 P ti trng tc dng ln bn nn, kg d- ng knh bn nn, cm S ln cui cng ca bn nn, cm - h s n hng ca t, i vi ct v ct pha l 0,3; i vi st pha l 0,35; i vi st l 0,42. SdPE ) 1 (2 =8.3.2.4. Th nghim nn hng Xc nh tnh cht bin dng ca t ct st trong cc h khoan. Phng php ny nhm o ln ca t to thnh h khoan di tc dng ca p lc 2 3

1 67 5 4 8 5 1 .Bnh kh nn; 2.Bnh o th tch;3. ng h o p lc;4.Bung cng tc;5. Cc bung ph; 6.ng dn nc; 7.ng dnkh; 8.Lcpthnhh khoan. M un bin dng xc nh theo cng thc: trong :do- gia s p lc; dr- gia s bin dng hng tm ng ng vi gia s p lc ro - bn knh ca bung di p lc ban u; - h s n hng.drdPr Eo. ). 1 ( + =8.3.2.5.Th nghim xuyn1. Th nghim xuyn ng Nguyn l ca phng php th nghim ny l cho qu ba nng 63.5+-1 Kgri t cao 76 cm. S ln ba ri ng mi xuyn vo t l 30 cm c coi l lc khng xuyn N (Theo TCXDVN tr s ny c k hiu l N30).Ph thuc vo iu kin khi th nghim ( su, tnh trng thit b, iu kin a cht thu vn) m s ln ba ng thc t N c th phi c hiu chnh cho ph hp( ) 152115 + = N NhDa vo kt qu th nghim (N, Nh), bng tin nh v cng thc thc nghim chng ta c th phn loi t, xc nh trng thi t, moun bin dng, gc ma st trong ca t ct, st ca t loi st, sc chu ti cho php ca t nn. V d theo TCXD 226-1999 kt qu xuyn SPT c din dch nh sau: i vi t ht ri c th da vo N30 xc nh cht tng i D, gc ma st trongv moun bin dng E theo bng v cng thc Terzaghi v Peck: ( ) 630 + + = N E | oTrong : -h s thc nghim bng 40 khi N30 >=15 v bng 0 khi N30 8040 - 45Rt cht i vi t dnh quan h gia N30 vi st v bn nn n hng qn nh sau: Bng 8.2 : Quan h N30 vi st v qn ca t dnh N30 stqn, kg/cm2 4,0 Bng 8.3 : quan h gia s ba nn vi cc ch tiu vt l, c hc ca t (khi xuyn su 30cm) Gc ma st trong0t dnht xp (C=0) S ba nn st BCng cho php S ba nn cht tng i D 0-2>10,0-0,250-40,0-0,1550>0,75>45 >300>4 2. Th nghim xuyn tnh Trong phng php xuyn tnh mi xuyn c n t t vo t di mt p lc nht nh. Ngi ta ghi li p lc cn thit xuyn mi xuyn vo t . Phng php xuyn tnh c p dng cho hu ht cc loi t. C 2 loi thit b xuyn tnh c v xuyn tnh in. Thit b xuyn tnh c s dng ph bin hin nay Vit Nam l xuyn cn CPT nh my xuyn Gauda H Lan. Kt qu th nghim xuyn c gm: sc khng u mi n v qc v sc khng st bn hng n v fs. i vi th nghim xuyn in ngoi hai i lng ny cn c th xc nh c p lc nc l rng.Da vo kt qu th nghim xuyn tnh (qc, fs) cng thc thc nghim v bng tin nh c th phn loi t, xc nh trng thi cht ca t ct, st ca t loi st, gc ma st trong ca ct, moun bin dng ca t ct, st v sc chu ti mng cc, mng nng. Bng 8.4 : Xc nh cht ca t ct theo sc khng n v u mi xuyn (tiu chun TCVN 174 1989 ) Loi ctqc (105 Pa) cht Ct ht th v trung150 < qcCht 50 < qc =< 150Cht va qc < 50Ri Ct ht mn120 < qcCht 40 < qc =< 120Cht va qc < 40Ri Ct ln bi100 < qcCht 30 < qc =< 100Cht va qc < 30Ri Ct bi bo ho 70 < qcCht 20 < qc =< 70Cht va qc < 20Ri 8.3.2.6. Th nghim ct quay (Vane test): Th nghim ct quay l phng php nh gi sc chng ct ca cc loi t yu nh : t loi st c st ln, than bn, mn hu c . . .54321hd1 . dng c ct c cnh. 2 . cn 3 . ng chng 4 . gi 5 . thit b o ca dng c, c c cu truyn ng lm quay cnh h. chiu cao cnh d. ng knh ca cnh . hnh di ta thy rng khi cnh quay, t b ct theo mt tr vi chiu cao h v ng knh d. Lc sc chng ct bng: Trong : - sc chng ct ca t kg/cm2 Mmax: mmen xon cc i, kg.cm K: i lng khng i ca cnh ct (cm3) ph thuc vo chiu cao h v ng knh d ca n: KMmax= t|.|

\| + =hd h dK3122tBng 8.5: Kch thc cnh ct v h s K S hiu loi cnh ct Chiu cao h (cm) ng knh d (cm) Chiu dy cnh o (cm) H s ct cnh K (cm3) BS 1377105.00.3458 1115.50.3610 2157.50.351545 3207.50.351978 42010.00.43663 HNH TRUHOKHOANPROJECT: ELEVATION OF GROUND WATERCong trnh: AT THE DRILLING TIMELOCATION (Vtr) : (Mc nc ngam thi iem khoan)BOREHOLE No (Hokhoan so): BH2APPEARANCE (Xuat hien): -3.0mTOTAL DEPTH OF HOLE (osau hokhoan): 14.0m DATE (Ngay o):TOP ELEVATION OF HOLE (Cao omieng ho): +0.0 STATIC (On nh): -4.5mSTARTING (Khi cong) : COMPLETION (Hoan thanh): 21 - 11 - 2000 DATE (Ngay o):DEPTH (in m)osa u (M)LAYER NAMETe n l pELEVATION (in m)Cao o(m)THICKNESS (in m)Beda y (m) SOIL GRAPHMAT CATA CHAT1/100S.P.T.Chu y tie u chua nSOIL DESCRIPTIONMOTAATSPT(N)SPT DIAGRAMBieu oSPT0 00.4 Xaban gach, cat, a1Set pha cat mau xam vang, 32 1 2.9 xam trang, trang thai deonhao - deo mem3 8Soi san laterite lan t set pha4 2 1.2 cat mau nau o, nau vangtrang thai na cng - cng 285 Set pha cat lan t soi san3 2.0 laterite mau xam trang, nau6 o, trang thai deo mem97 Set pha cat mau xam trangom vang nhat, trang thai8 4 2.3 deo mem9 7103.6 Cat mn lan bot mau vang11 5 nhat, trang thai chat va 15122513 Cat thoen mn lan t bot6 1.6 mau vang nhat, trang thai14 chat va 1815 ay hokhoan 14.0m16171819BORE HOLE LOG3828971525180 102030 4050 >60-0.40.0-3.3-6.5-8.8-12.4-4.5m 5 . 2 0 . 23 2434m 0 . 4 5 . 35 2141314m 0 . 6 5 . 57 2445m 5 . 8 0 . 89 2334m 5 . 10 0 . 1011 2758m 0 . 12 5 . 1113 2121113m 5 . 13 0 . 1315 2989m 0 . 1