tcxdvn 366-2004 công tác khảo sát Địa chât cho công trình vùng kaster

www.vncold.vn Hi p ln Vit Nam

TCXDVN Tiu chun xy dng Vit nam

TCXDVN : 366: 2004

ch dn k thut cng tc kho st a cht cng trnh

cho xy dng trong vng karst Technical regulation of engineering geological investigation for construction in karst areas


2

H Ni - 2006

Mc lc. Li ni u 1.Nhng vn chung .............................................. ............................................. 5 1.1 Phm vi v i tng p dng....................................................................... .5 1.2 Thut ng v nh ngha ...................................................................... . ..5 1.3 Ti liu trch dn .. 6 1.3 c im hnh thnh, pht trin karst............................................................. . .6 1.4 c im diu kin CCT trong vng karst................................................... ..7 2. Phng php kho st CCT trong vng karst.............................. ..... 9 2.1 Thu thp, phn tch v tng hp s liu kho st c ...................................... 9 2.2 S dng cc ti liu vin thm...................................................... ................ ..10 2.3 Phng php o v trc a cng trnh..............................................................10 2.4 Phng php kh tng thu vn - cng trnh....................................... ... 11 2.5 Phng php o v a cht cng trnh.......................................................... . 11 2.6 Phng php thm d a vt l............................................................ . 13 2.7 Phng php khoan v khai o............................................................... ... 15 2.8 Phng php nghin cu a cht thu vn............................................ 17 2.9 Th nghim t ti hin trng................................................................ ... 19 2.10 Th nghim trong phng v nghin cu th nghim..................................... ..19 2.11 Quan trc nh k.......................................................................................... ..21 2.12 X l s liu................................................................................................... .22 3 Kho st CCT giai on trc thit k c s......................................... .. 22 3.1 Mc tiu kho st .. 22 3.2 Nhim v kho st 23 3.3 Ranh gii kho st .. 23 3.4 Ni dung v khi lng kho st 23 4. Kho st CCT giai on thit k c s...................................................... .25 4.1 Mc tiu kho st 25 4..2 Nhim v kho st . 25 4. 3 Ranh gii kho st 26 4.4 Ni dung v khi lng kho st 26 5. Kho st CCT cho giai on thit k k thut............. ............................ ..31 5.1 Mc tiu kho st 31 5..2 Nhim v kho st . 31 5.3 Ranh gii kho st .. 32 5.4 Ni dung v khi lng kho st 32 6. Kho st CCT giai on thit k bn v thi cng ...............................36


3

6.1 Mc tiu kho st .36 6..2 Nhim v kho st ..36 6.3 Ranh gii kho st ... 37 6.4 Ni dung v khi lng kho st 37. Ph lc A. nh gi iu kin CCT trong vng karst.................................41 Ph lc B. Phn loi theo mc nt n...................................................... ...81 Ph lc C. Phn loi theo mc phong ho ..................................................82 Ph lc D. S phn b cacbonat v pht trin karst lnh th Vit Nam 83


4

Li ni u TCXDVN 336:2006 Ch dn k thut cng tc kho st a cht cng trnh cho xy dng trong vng karst c B Xy dng ban hnh theo Quyt nh s: ngy......thng.....nm 2006


5

Tiu chun xy dng Vit Nam (1) TCXDVN: 366:2006

Bin son ln:1.

Ch dn k thut cng tc kho st a cht cng trnh cho xy dng trong vng karst Technical regulation of engineering geological investigation for construction in karst areas

1. Nhng vn chung

1.1 Phm vi v i tng p dng 1.1.1 Ch dn ny dng lm c s lp nhim v kho st a cht cng trnh (CCT) cho xy dng trong vng karst. i tng p dng l cc khu cng nghip, cc khu dn c, th (goi tt l cng trnh), khng p dng cho kho st xy dng cc cng trnh c bit nh: cc cng trnh dng tuyn, cc cng trnh thu li-thu in, cc cng trnh ngm,...

1.1.2 Kho st CCT trong vng karst khng tch ri cng tc kho st chung cho xy dng v c tin hnh trong 3 giai on, tng ng vi 3 giai on thit k xy dng c quy nh trong cc quy ch hin hnh: thit k c s (TKCS); thit k k thut (TKKT); thit k bn v thi cng (TKBVTC). Trong trng hp cn thit phi b sung thm giai on kho st CCT trc TKCS.

1.1.3 Cng tc kho st CCT phi c thc hin trn c s cng kho st CCT. Ni dung ca cng phi m bo tho mn cc yu cu nghin cu, lp h s cho cc giai on thit k tng ng. Ch dn ny c th p dng kho st phc v sa cha, m rng, nng cp x nghip v cng trnh.

1.1.4 Karst trn lnh th Vit Nam pht trin ch yu trong cc cacbonnat, v vy trong phm vi ca ch dn ny ch xt n cc vng pht trin karst trn cacbonat ( vi, olomid, macn). Cc khu vc nu c hang hc loi khc (v d cc hang hc trong t st hnh thnh do t c kh nng tan r mnh) khng phi l i tng c quan tm trong ch dn ny. 1.2 Thut ng v nh ngha 1.2.1 Karst l t hp cc qu trnh v hin tng a cht xut hin trn b mt hoc trong lng t ch yu l do ho tan ho hc t , to nn cc hang rng, lm ph hu v bin i cu trc, trng thi t , c ch nc ngm, c th a hnh, c ch mng thu vn.


6

1.2.2 Vng karst l cc khu vc m trn mt ct a cht ca chng c mt t ho tan ( vi, dolomid, macn, mui, ) v c hoc c th xut hin karst trn mt v karst ngm.

1.2.3 Karst trn v karst ph l hai loi karst phn bit theo c im phn b ca b karst ho. karst trn ( b karst ho nm ngay trn mt) v karst ph ( b karst ho b che ph bi cc lp t khng ho tan, khng thm nc hoc t khng ho tan c thm nc).

1.2.4 St l - karst l hin tng sp mt t do hang karst su khng ln, trn hang yu. Xi st l - karst l hin tng sp mt t do dng nc mang cc vt liu ca tng ph nm trn a xung hang gy sp lp ph bn trn (dng thm i xung). St l - xi st l - karst l t hp ca c 2 loi hnh nu trn.

1.2.5 L khoan su l h khoan nghin cu karst c chiu su vt qua vng b karst ho vo tng nm di nguyn khi khng nh hn 5m. 1.3 Ti liu trch dn TCVN 4419 : 1987. Kho st cho xy dng Nguyn tc c bn TCVN 4253-86. Phn loi khi TCXD 13: 1991. Phn cp cng trnh xy dng. 1.4 c im hnh thnh, pht trin karst

1.4.1 Nhng yu t c bn pht trin karst bao gm: s vn ng ca nc ngm v nc mt; tn ti t ho tan; tnh thm nc ca t ho tan (t phi c kh nng thm nc); kh nng ho tan t ca nc.

Ch cn thiu d ch 1 trong cc yu t k trn th karst khng pht trin, v khi hi t

c 4 yu t th s pht trin ca karst l khng trnh khi.

Cc yu t nh hng n s pht trin karst bao gm:thnh phn thch hc ca ho tan; chiu dy v c im nt n ca lp ho tan; thnh phn v chiu dy ca lp

ph; a hnh; iu kin kh hu.

1.4..2 Karst c quy lut pht trin chung l : gim dn theo chiu su; mnh hn thung lng sng v yu hn khu vc phn thu; ph thuc vo c im cu trc v lch s pht trin a cht ca khu vc.

Cc loi hnh karst b mt ph bin c th k n nh: ho, rnh karst, cc b mt ho tan st vi cc hang ni, hang chm; phu karst (ra tri b mt, ln, sp tng mt);

cnh ng karst (tp trung nhiu phu karst); thung lng karst (do hot ng xm thc bng


7

nc mt v nc ngm); vc karst (do sp nc cc sng ngm hoc hp nht cc h su karst to thnh vc su khp kn c vch dng ng, y bng phng); rng karst (to ra

do s k tip lin tc ca cc rnh su vi nhng khi cn li); sng, sui, h cn, h

ni karst; ging karst, h thu nc karst.

Cc loi hnh karst ngm ph bin bao gm: khe nt m rng do ho tan; l rng ho tan (nh hn 2mm); l hng ho tan (220mm); hang hc cc loi (ln hn 20mm, trong c c hang ng, h v sng ngm); cc i ph hu v d ti; b mt ho tan cc lp karst ho; cc ph hu th nm ca t nm trn cc hang hc v cc i ph hu karst; phu v a hnh karst c b che khut. 1.5 c im iu kin CCT trong vng pht trin karst 1.5.1 Kho st CCT trong vng pht trin karst cn ch : kh nng pht sinh bin dng t nn v b mt t do pht trin karst; kh nng chu ti ca t b karst ho gim khng u, c ch tn ti cc i hoc cc thu knh yu trong tng ph; c im thu vn (TV) v a cht thu vn (CTV) lin quan vi karst bin i rt mnh v phc tp; kh nng kch thch pht trin karst v cc qu trnh a cht ko theo khc do hot ng kinh t ca con ngi.

1.5.2 Bin dng t nn v b mt t trong vng karst chia lm cc loi: sp mt t, ln mt t cc b, ln mt t khu vc.

Cc h sp c th xut hin n l hoc thnh nhm, c th l mi, c th l nhc li ch c trong c th nhc li nhiu ln. Theo thi gian, cc h sp b lp dn.

Ln mt t cc b do karst pht trin chm hn sp, t vi gi, vi ngy n vi nm v hnh thnh trn mt t ch un vng, thung lng, phu ng knh t vi mt n vi chc mt, chiu su t vi cm n 1-2m, thm ch i khi vi mt.C ch ln mt t cc b cng nh sp nhng chm hn, thng hay xen k vi sp th sinh.

Ln mt t khu vc l qu trnh a cht lu di do dch chuyn t pha trn vng pht trin karst, c bit l t pha trn b mt b xm thc (ho tan) v do mang dn vt liu ri t t tng ph theo cc khe nt v hang hc karst. Ln mt t khu vc xy ra vi vn tc qu nh ch phi xt n khi thit k cc cng trnh c bit, nhy cm vi ln nn.

Trong vng pht trin karst ngoi sp, ln cn tn ti cc dng a hnh karst khc nh k phn trn: phu, trng, ho, rnh lng ng v tch cha cc vt liu chu ti km, trong c c t san lp, bn.

1.5.3 Nu trong vng nn ln ca cng trnh c gc b karst ho th phi nh gi kh nng chu ti ca chng, phi tnh n mc nt n v khng ng nht v nt n, s c


8

mt ca cc i gc yu do ra la v do hang hc (c lp nht hoc khng lp nht). Cng cn phi tnh n kh nng tn ti cc ph hu khc (do karst) trong t khng ho tan nm trong vng nn ln (hang hc b lp nht hoc khng b lp nht, cc i d ti, cc i dch chuyn v t gy).

1.5.4 iu kin CTV v TV trong vng karst c trng bng nhng tnh cht rt ring bit (tnh thm ca b karst ho cao v rt khng ng nht, c im phn chia dng chy mt, dng chy ngm, c ch mc nc, c im bin i thu a ho rt phc tp, tn ti cc h thu nc mt, cc khu vc mt nc t h cha v cc dng chy ngm bt ng chy vo h o ) phi rt ch khi kho st nh gi lnh th. Nhng c trng ny c ngha quan trng khi thit k cc h cha nc, h thng knh mng, ti tiu, thi v gii quyt cc nhim v khc, bao gm c cc gii php x l karst.

1.5.5 iu kin xy dng v kho st trong vng karst ph thuc vo nhng quy lut v c im t nhin mang tnh khu vc, a phng v cc b. Nhng quy lut v c im ny rt khc nhau i vi cc loi karst khc nhau theo thnh phn thch hc, th nm ca karst ho v cng rt khc nhau cho cc vng kin to, kh hu khc nhau.

1.5.6 Vng pht trin karst trn c nhng c im sau: s xut l trn b mt cc b karst ho lm cho nc mt thm xung, pht trin phong ho, hnh thnh cc khe nt ngoi sinh v pht trin karst; sp v h thp mt t l do b v v st thnh vch cc h karst. Sp v ln mt t do xi ngm - karst ch quan st thy cc vng a hnh h thp c lp y bng t mm ri; kh nng chu ti ca ni chung l cao nhng khng u, i ch rt yu. Do l ngay trn mt nn tin hnh kho st CCT trong trng hp ny rt hiu qu, c th phn vng CCT karst mt cch d dng.

Vng pht trin karst kn b che ph bi t khng ho tan v khng thm nc th t khng thm nc bn trn ngn cn qu trnh pht trin karst v cc qu trnh lin quan khc. Kho st CCT trong trng hp ny cn phi xc nh kh nng thm nc v chiu dy tng ph, nh gi kh nng bo v b mt t ca tng ph ( bn) khi cc hin tng karst b mt.

Vng pht trin karst kn b che ph bi t thm nc khng ho tan th lp t thm nc khng ngn cn qu trnh pht trin karst v cc hin tng lin quan, n cn gy kh khn cho vic kho st v nh gi phn loi lnh th theo karst, c bit nguy him l cc khu vc m lp ph l t loi ct, sn, si. Trong trng hp ny karst pht trin mnh thung lng sng, cc dng chy ngm c gradien rt ln xut l y sng v sn thung lng, qu trnh xi ngm-karst pht trin mnh, c th hnh thnh cc phu karst lm h hi v ph hu cng trnh. Nhng tc ng nhn sinh trong cc khu vc ny (c bit l nhng bin i v ch ng lc nc di t do khai thc nc ngm) s lm pht trin mnh cc qu trnh xi st l karst.


9

Kho st CCT trong vng karst kn i vi tng ph phi xc nh c: cu trc a cht, thnh phn thch hc, trng thi, tnh cht ca t , iu kin CTV, cc biu hin karst b mt, cc i ph hu v d ti.

1.5.7 Kho st CCT trong vng karst cn ch rng thay i trng thi t nhin do kt qu hot ng kinh t ca con ngi c th dn n vic pht trin mnh karst cng vi cc qu trnh c lin quan, v d : thay i iu kin thu ng lc nc di t do xy dng thu in, khai thc m, khai thc nc ngm thng lm gia tng t ngt qu trnh xi st l karst; thay i tnh n mn ca nc ngm do nc thi cng nghip cng dn ti pht trin mnh karst; ti trng ng c th gia tng cc qu trnh sp mt t trong macn, lm gim sc chu ti ca , thm ch gy ho lng i vi t...

1.5.8 nh gi s b mc phc tp ca iu kin CCT trong vng karst phc v thit k kho st c th kt hp bng phn cp mc phc tp ca iu kin CCT trong tiu chun kho st TCVN 4419:1987 vi nh gi mc v c im pht trin karst theo bng A1, A2 ca ph lc A. Cp ca cng trnh xy dng c cp trong ch dn ny xc nh theo tiu chun xy dng TCXD 13: 1991.

Nhim v c bn ca kho st CCT trong vng karst l: xc nh mc nguy him ca karst tc ng n cng trnh, mi trng sinh thi v kinh t x hi; d bo pht trin karst trong giai on xy dng v s dng cng trnh; xc nh kh nng kch hot karst trong qu trnh s dng cng trnh do cc tc ng nhn sinh; son tho chin lc v cc kin ngh c th cho cc gii php x l karst. T khi xy dng k hoch, lp cng v tin hnh kho st cn ch nhng im sau: qu trnh pht trin karst v cc hin tng i km (xi ngm, sp, h thp mt t) c quyt nh bi t hp nhiu yu t c mi lin h tng tc v phc tp; karst pht trin v phn b rt khng ng nht theo thi gian v khng gian; vng pht trin hang hc karst nguy him cho cng trnh c th nm nhng su ln (50 100 m, i khi cn hn ) i hi phi c cc l khoan chuyn dng nghin cu; quy lut phn b v pht trin karst khng th lm r c khi tin hnh kho st trn mt din tch khng ln. 2. Phng php kho st CCT trong vng karst. Mt s yu cu k thut Kho st CCT trong vng karst phi c tin hnh theo th t cng vic v kt hp ti u cc phng php kho st: thu thp, phn tch v tng hp ti liu kho st ca nhng nm trc ( trong c c cc s liu v kinh nghim xy dng v s dng nh, cng trnh trong vng karst); phn tch bn a hnh t l ln v nh my bay; trc a cng trnh; kh tng-thu vn cng trnh; o v a cht cng trnh (CCT); a vt l (VL); khoan - khai o; a cht thu vn (CTV); th nghim t ngoi tri, bao gm c xuyn


10

ng, xuyn tnh v karota; th nghim trong phng v nghin cu thc nghim; quan trc; x l s liu. 2.1 Thu thp, phn tch v tng hp s liu kho st c Thu thp, phn tch, tng hp s liu v cc vng karst gii quyt cc nhim v sau: lm sng t cu trc kin to, lch s a cht khu vc, chiu su phn b, loi hnh v tui ca karst; nghin cu mt ct a cht-thch hc khu vc thm d v vng ph cn trn ton b chiu dy tng ph v chiu su i pht trin karst; pht hin cc i kin to yu; nghin cu iu kin a cht thu vn, thu vn, a mo pht trin karst; thu thp cc bng chng v cc c tnh nh lng v karst trn b mt v di su, v bin dng cc cng trnh xy dng, nh , khai thc nc, v nhng bin i trng thi mi trng t nhin cng nh tc ng ca chng n qu trnh pht trin karst trn lnh th nghin cu. Ch trng n nhng biu hin ca cc h sp karst v bin dng mt t trong khu vc.

Khi thu thp v h thng ho t liu cn tin hnh ng thi vic ghi ch danh mc ti liu s dng, sao chp cc bn , mt ct, th, biu bng.Trn c s thu thp, phn tch, tng hp t liu phi thnh lp: bn ti liu thc t; bng tra cu l khoan kho st; cc kt qu nghin cu a vt l, thu vn, a cht thu vn, th nghim trong phng v ngoi tri, quan trc nh k;katalo cc dng a hnh karst (phu, h sp, ); s phn tch iu kin pht trin v phn b karst; s phn vng s b lnh th theo iu kin, c im v mc pht trin karst.

Thu thp s liu phi c tin hnh trc mi giai on kho st. Nhng ti liu thu thp k trn lm c s hoch nh k hoch kho st tip theo, la chn ni dung v khi lng hp l cng nh phng php kho st thch hp. 2.2 S dng cc ti liu vin thm Cc ti liu vin thm c s dng giai on u kho st cho cc cng trnh c quy m ln. Cc t liu vin thm c s dng o v a cht, a cht thu vn v a mo nh hng n qu trnh pht trin karst, o v cc cu trc karst v quan trc qu trnh pht trin ca n. nh hng khng t l 1:5000 1:20000 cho php gii on vi tin cy cao cc dng cu trc a hnh karst ti nhng khu vc khng c dn c sinh sng (phu, h sp karst ...) vi kch thc tng ng ln hn 5-20 m. Trn nh hng khng cho php xc nh cc h st, phu karst b lp m kho st mt t khng nhn thy.Ti cc khu vc c dn c sinh sng, t liu nh vin thm c th cho php gii on cc dng a hnh hoc mt qun th a hnh karst c kch thc ln. 2.3 Phng php o v trc a cng trnh o c trc a cng trnh phc v nghin cu a hnh khu vc s xy dng v cung cp s liu thit k cc hng mc xy dng v kho st cng trnh .Trong vng karst phi


11

c bit ch trng vic o c v th hin c cc biu hin karst trn s , bn mt bng khu vc kho st, nh v to mt bng, cao trnh ca cc cng trnh khoan o, ca cc im quan trc (a vt l, thu vn,..) khc, o v mt ct, mt bng a hnh cho tng cu trc karst phc tp, quan trc trc a nh k v bin dng cng trnh xy dng, bin dng b mt v cc lp t .

2.4 Cc phng php kh tng thu vn - cng trnh Kho st kh tng thu vn l b phn khng th thiu i km vi cc kho st a cht thu vn v cc cng tc kho st khc. Kho st kh tng thu vn khng ch tin hnh trong cc giai on kho st m cn trong h thng quan trc nh k tip theo. Nhim v kho st kh tng-thu vn bao gm: lp cn bng nc v mui, nh ga cng hot ng karst; lm sng t v nh lng cc khu vc thu nc mt v cc khu vc nc mt c b sung bng nc ngm; nghin cu ch ng lc nc mt v nh hng ca nc mt n pht trin karst; d bo nhng quy lut thu vn nh gi s pht trin ca karst trong tng lai v tnh ton nh hng ca cc tc ng nhn sinh. Cn ch rng trong vng pht trin karst, c im thu vn bin i rt mnh theo din cng nh thi gian (cc phu thu nc mt, cc ngun nui nc mt bng nc ngm, s dao ng bt thng ca ch nc mt).

2.5 Phng php o v a cht cng trnh o v CCT trong vng karst, bn cnh nhng nhim v CCT thng thng cn phi gii quyt nhng ni dung c th sau: xc nh s xut hin cc loi hnh karst trn mt t; cc biu hin thu vn, CTV pht trin karst; mi quan h ca karst vi cc yu t a cht kin to, a mo, a cht thu vn; bin dng nh v cng trnh lin quan vi karst; kinh nghim v hiu qu ca cc gii php x l karst; cc yu t tc ng nhn sinh kch hot karst (cc trm bm nc ngm, h thng dn nc, cng trnh thu cng). T l o v ph thuc vo: giai on kho st, quy m v tm quan trng ca cng trnh, mc phc tp ca iu kin CCT v cc kt qu nghin cu.

Ti nhng khu vc c nn a cht, a cht thu vn cng t l o v CCT th o v CCT c tin hnh ch kim tra v chnh xc ho cc t liu v iu kin a cht, CTV, a mo. Trong trng hp khng c cc t liu ny, cn phi tin hnh o v a cht, a cht thu vn, a mo vi ni dung p ng yu cu ca nhim v kho st CCT t ra.

Vic nghin cu iu kin pht trin karst v mc karst ho ti cc im l gc t nhin v nhn to c ngha c bit quan trng. Nghin cu cc i tip xc gia t c ngun gc thch hc v thnh phn khc nhau, nhm xc nh r lch s a cht ca khu vc, trong c vn karst c v cng l lm sng t kh nng pht trin karst trong th im hin ti. c bit ch nghin cu a hnh b mt ca gc v cc thung lng c,


12

cc bin i dy tng v lm sng t mi lin quan ca cc bin i ny vi karst. Pht hin cc phn lp chn nc v tng khng ho tan. Xc nh cu trc, thnh phn t , phn b v tnh cht ca tng ph lm r kh nng pht trin cc qu trnh ph hu, sp, ln v.v..., thc y bin dng b mt.Nghin cu nt n ca t trong cc vt l, ho, h o tin hnh cc phn tch thng k sau ny. Ly mu t, , nc mt, nc ngm cho cc th nghim trong phng.

i vi mi biu hin karst trn mt (phu, h sp) phi c m t y cc c tnh: hnh dng trn mt bng (trn, van, ng phng hay khng); ng knh, su, phng trc di, trc ngn; c im ming phu ( phng, gc cnh , r hay m, nhn hay khng); dc ca thnh phu; hnh dng y, mc cha nc v ly ho; mc che ph thc vt trn sn dc v y; m t cc im xut l gc, mc nt n ca chng, cc h thu nc.

Khi iu tra cc trng lng cho, khe xi, thung lng v cnh ng karst phi nghin cu hnh hi ca chng v mi lin h vi nc mt, nc ngm. Trong phi m t hnh thi, kch thc, c im sn dc, y, cc im l gc, s hin din ca cc phu karst, h thu nc, ngun nc xut l, khu vc ng ngp vo ma ma v.v Cn phi iu tra, khng nh yu t khp kn, na khp kn hay m (c ca trao i t do vi nc mt), khoanh vng cc dng karst thu nc khp kn. Nn tin hnh phn tch lch s a cht qu trnh hnh thnh cc loi hnh karst ang th st.

Trong qu trnh m t ho-rnh, cnh ng karst, phi th hin mt rnh, hng pht trin ca chng, hnh hi, kch thc v c hay khng cc tn tch tn ti trong cc rnh, mi lin quan gia ho-rnh v thnh phn thch hc, mc nt n v a mo.

i vi cc hang ng karst cn v s mt bng, mt ct ngang, mt ct dc hang, xc nh hin trng tn ti ca hang: a cht-thch hc ca hang, cu trc kin to, a mo , cao hang, tui, thnh phn, iu kin th nm, c im cu to v tnh cht ca t trn tng, trn nc v di y hang ng, nt n, phn ct, c im b mt vt nt. Lu n cc sui h ngm, nc ng trn thnh v trn hang ng, cc nh ct, nh chung, vt liu ct, st trong khe nt v y hang ng. Xc nh mi lin quan gia hang ng vi cc phu karst c trong khu vc kho st.

Cc h karst cn m t v tr, kch thc, su, hnh dng, lm r iu kin thnh to h, mi lin quan vi tng thch hc, iu kin cp nc (nc mt, nc ngm hay hn hp), thot nc, ch , mc nc v thnh phn ho hc ca nc trong h, c hay khng phu, ngun nc ngm di y h v trn b.


13

Cc sng v h ngm cn xc nh kch thc ca chng, vn tc dng chy, lu lng trn tng on, nhit , thnh phn ho hc, lm r ngun cp v c im ch nc. Xc nh cao trnh mc nc v mi lin h vi a tng thch hc.

Cc sng sui hin-n cn ghi nhn ch ng lc ca chng (thng xuyn, chu k), lu lng dng chy, v tr thu nc v c im vn chuyn t nc mt sang nc ngm, thnh phn ho hc v nhit nc.

Cn thu thp cc s liu v nh hng ca cc tc ng nhn sinh n ch v c tnh n mn ca nc ngm, cc s liu v ph hu v mt n nh ca t trn cc hang hc karst ngm do ph ti ca cc cng trnh, do tc ng ca my mc, h thng giao thng v.v, cc s liu v bin dng nh - cng trnh v mi lin h ca chng vi cc loi hnh karst trn mt t v di su, c im nt n ca t v.v, cc s liu v cc qu trnh a cht ng lc khc v mi tng quan gia nhng qu trnh ny vi hin tng karst.

Cn thu thp ti liu ca cc c quan qun l hnh chnh a phng v trong dn c, nhng chng c v st, ln mt t, v bin dng cc cng trnh xy dng, v kinh nghim xy dng v s dng cng trnh, v cc bin php phng chng, x l karst v hiu qu ca chng.

Trong qu trnh o v cn xc nh cc iu kin cp thot nc ngm, khoanh nh vng thu nc, m t v o v cc ngun xut l nc (mch nc, ging, l khoan, khu vc ly ho), Ly mu nc phn tch thnh phn ho hc v c tnh n mn. c bit ch cc mch nc karst, thu nc mt, h karst, dng chy trong hang ng Nu c sn ngun t liu v CTV, cn tin hnh kim tra, chnh xc ho v xem xt kh nng bin ng iu kin CTV so vi s liu c trc. Khi m t cc ngun nc karst cn ch r v tr, yu t a mo m chng tn ti trong , cao, kiu (chy ra, n ln hay vo), lu lng v c im ngun nc (thng xuyn, bt thng, c chu k..). Xc nh mi quan h gia ngun nc vi cc tng cha nc v vi cc biu hin karst khc. Nu ngun nc chy t cc khe nt, cn xc nh ngun gc ca cc khe nt , kch thc, gc dc, phng v.

Kt qu o v CCT v karst phi th hin trn bn k c nhng biu hin karst b che ph , nhng biu hin karst kho st t nhng nm trc.

2.6 Phng php thm d a vt l Trong vng karst cc phng php a vt l c s dng gii quyt nhng ni dung sau: xc nh chiu dy, thnh phn v iu kin th nm ca lp ph v karst, nghin cu a hnh karst dng trng thp; xc nh chiu su mc nc, hng v vn tc dng chy ca nc karst, khong ho, min cp, min thot ca chng; o v hang hc


14

v xc nh mc karst ho, mc ph hu ca t , cc i ph hu kin to v dp nt, cc i d ti trong tng ph v trong tng karst v cc d thng khc

Ch : Cc phng php v thit b kho st a vt l trn mt t cho php xc nh hang hc karst khi quan h gia su phn b ca chng vi ng knh (h/d) khng vt qu1-2 v nu chng ni bt mt cch tng phn gia cc xung quanh bi nhng tnh cht vt l ca mnh. Cc phng php nghin cu khong khng gn l khoan, khong khng gia cc l khoan cha c nghin cu y v cng c nhng hn ch lin quan n kch thc v tng phn th hin trong cc trng a vt l ca cc hang hc cn tm.

Kho st VL trong vng karst thng s dng cc phng php sau: Thm o in (mt ct in, o su in); thm d a chn; thm d trng lc; thm d m thanh; o in tr nc mt, nc ging; cc loi carota l khoan (in, phng x, m thanh); o hng, lu lng, nhit v in tr trong l khoan; v cc phng php khc. 2.6.1 Thm d in c coi l phng php c ng, n gin, tit kim v hiu qu. Nguyn tc ca thm d in l da trn c s bin i in tr sut ca t trong khng gian, v vy cc phng php c bn s dng trong thm d in l: o mt ct in, o su in, carota in tng hp. o mt ct in (theo cc tuyn mt ct) c s dng nghin cu a hnh karst dng trng thp-rng lc, phc tp v khoanh vng cc hang hc karst, cc i xung yu nm su khng ln (di 10-15 m). o su in c s dng nghin cu su, cc yu t th nm, chiu dy v cu trc ca tng karst v cc biu hin karst ( hang hc, nt n ) c xc nh bng phng php o mt ct in. Carota in tng hp trong cc l khoan bao gm: in tr biu kin, in trng t nhin, phn cc cng bc, o khng tr, carota bin, carota bin lp, vi thm d cho php xc nh chnh xc mt ct a cht-thch hc l khoan, phn chia trong cc i ph hu v nt n, xc nh chnh xc su , chiu cao v c im cht lp nht hang hc karst,phn on theo chiu su l khoan cc khu vc ht nc, cc khu vc nh nc, xc nh khong ho ca nc. Ngoi ra xc nh cc i nt n, cc hang hc karst, hng v vn tc chuyn ng ca nc ngm trong khong khng gian gn l khoan, nn s dng phng php vt th tch in, cn i vi trng hp gia cc l khoan v gia cc cng trnh khai o khc th s dng phng php chiu in v chiu sng v tuyn in. 2.6.2 Thm d trng lc nghin cu karst da vo s khc nhau c bn v dung trng ca t tng ph, cht lp nht, nt n-l rng v nguyn khi. V vy o v trng lc chnh xc cao, thc hin theo cc ch dn hin hnh c th gii quyt c cc bi ton


15

xc nh cc cu trc kin to, cc thung lng sng b chm su, su phn b ca b mt karst, cc hang hc ln hoc cc i ph hu mnh. 2.6.3 Thm d a chn da trn c im phn b sng n hi trong t c thnh phn thch hc, trng thi , nt n v pht trin karst khc nhau. Thm d a chn bao gm: thm d a chn t mt t (o mt ct a chn, o su a chn) v thm d a chn trong l khoan (carota a chn v truyn sng a chn gia cc l khoan). Thm d a chn gii quyt c cc bi ton xc nh cu trc a cht (c bit l ranh gii tng ph vi gc), dy tng ph, tng karst, mc nc ngm, xc nh hang hc karst trong iu kin thun li. 2.6.4 Thm d m thanh bao gm: carota siu m l khoan v truyn m gia cc l khoan nhm gii quyt cc nhim v phn chia mt ct l khoan theo thnh phn thch hc, pht hin cc i d ti, hang hc karst, trng thi ng sut ca t , mc khng ng hng ca t trn c s phn tch c im sng siu m (vn tc sng siu m b mt v sng dc, chu k v bin sng theo chiu su). 2.6.5 Thm d t c kh nng tm kim hang hc karst c lp nht bi cc vt liu c t tnh cao nh b-xit vn c cc phu trng karst. Thm d t l phng php thng thng c hiu qu tt trong kho st CCT ti cc khu vc m khong sn. 2.6.6 Georadar l phng php mi, c trin vng trong nghin cu karst, nhng cha c kim tra thc t. Phng php Georada (GPR) s dng sng rada di tn 1-1000MHz nghin cu cu trc v cc c tnh ca vt cht bn di mt t vi phn gii cao. S liu v kt qu kho st ca GPR biu din di dng mt ct cu trc vi nhng thng s vt l c trng cho mi trng a cht nh: in thm, vn tc v thi gian truyn sng, dn in, h s suy gim ca sng in t.. Phng php GPR s dng trong kho st CCT vng karst vi nhim v: xc nh cu trc a cht, xc nh cc i xung yu, cc i d ti, cc hang hc karst 2.6.7 o in tr nc h v ging C s ca phng php ny l s ph thuc r nt ca in tr sut ring ca nc vo khong ho ca n, v vy theo hm lng tng khong ca nc c th xc nh min tho nc ngm v cc khu vc thu nc b mt. y l phng php o nhanh, nng xut cao v rt c hiu qu trong kho st karst. 2.6.8 o nhit trong cc h cha nc, sng sui, ngun nc, ging v trong l khoan thng c tin hnh cng vi o khng tr v cc nghin cu thu a ho khc. y l phng php hiu qu pht hin cc ngun cp v min thot di y h v y sng. 2.6.9 Nghin cu carota phng x l khoan c th thc hin ti bt k l khoan no: ngp nc hay kh ro, c ng chng hay khng c ng chng v bao gm cc phin bn khc nhau: gamma-carota c p dng nh gi thnh phn vt liu st ca t , gamma-gamma-carota nh gi dung trng ca t , neutron-neutron-carota v neutron-gamma-carota nh gi m ca t . Cc s liu ny cho php nh gi mc nt n v mc karst ho ca theo mt ct l khoan, k c c tnh vt liu lp nht hang hc


16

v vt nt, phn chia chi tit mt ct a cht-thch hc, nh gi bo ho nc ca t . 2.6.10 Kho st kh radon - toron trong cc lp ct-st gn b mt t (t 0.51.0m) trn khu vc kho st c th xc nh c cc i nguy him do karst. S xut hin cc cc tiu trn phng kh bnh thng chng t nhiu kh nng c i nt n v pht trin karst. 2.6.11 o ng knh l khoan, o lu lng nc trong h khoan theo chiu su bng cc thit b chuyn dng gi l cc thit b o hng v thit b o lu lng cho php nh gi trng thi t thnh h khoan, xc nh kch thc cc hang hc karst v mc lp nht ca chng, ng thi xc nh cc i c kh nng thm nc khc nhau v cc thng s CTV tng ng. 2.7 Phng php khoan v khai o Cng tc khoan khai o gii quyt nhng nhim v sau: nghin cu cu trc a cht ca khu vc; nghin cu iu kin CTV; nghin cu thnh phn, trng thi, tnh cht ca cc loi karst, c tnh nt n, rng, mc pht trin karst, lm r cc hang hc karst, cc i ph hu; nghin cu thnh phn, trng thi v tnh cht ca lp ph (bao gm c cc hang hc, cc i d ti, thu knh t yu); ly mu t v nc th nghim trong phng; th nghim CTV, CCT, VL; quan trc nh k; khoanh vng cc khu vc c mc pht trin karst khc nhau.

Khi lng khoan khai o c xem xt trong cc giai on kho st, trong s lng tng th phi c mt s h khoan su dng nghin cu karst (cng c quy nh trong cc giai on kho st). Chiu su cc h khoan phi vt qu vng nh hng d kin ca cng trnh t 1-2m. Nu chiu dy ca vng b karst ho ln hn 5-10m cho php khng cn khoan ht chiu dy nhng phi c ln chng trong cng. Trong nhng vng c tng ph l t khng ho tan, khng thm nc cn phi nh gi mc thm nc v kh nng bo v ca chng khi cc biu hin karst trn mt t, nu chiu dy tng ph bo v c mt t khi cc biu hin karst th cho php khng khoan vo karst ho m ch gii hn vic kim tra b dy ca lp ph bo v, nhng phi c lun chng trong cng. Mng li h khoan phi c thit k theo kt qu o v CCT, thm d VL mt t v ph thuc vo mc phc tp ca iu kin CCT, cp v quy m ca cng trnh xy dng.

Cng ngh v phng php khoan phi m bo ly c ti a li khoan t tng ph, tng karst v vt liu lp nht. Khng c s dng phng php khoan ph, khoan gung xon v bt k kiu khoan no khc khng m bo thu nhn li khoan di dng mu hnh tr .

Khoan ly mu trong cng th tt nht bng khoan ra hoc thi kh, trong t d b ra xi - khoan tun hon ngc hoc khoan kh v rt ngn hip khoan xung 0,5-1,0 m. i vi yu, b ph hu, nt n mnh, vt liu lp nht hang hc cn p dng ng


17

khoan nng i v ng mu. Ch cho php khoan vi dung dch st trong trng hp tht s cn thit, vi iu kin khng mang li thit hi c bn no cho cng tc nghin cu a cht thu vn. i vi t loi st, t loi ct khng bo ho hoc ngm t nc th phng php khoan p vi dao vng rt c hiu qu, cc mu t b ri phi c ly bng ng mu hoc ng khoan nng i.

Ly mu v m t li khoan tin hnh theo cc quy nh bt buc hin hnh. Cn tin hnh m t li khoan mt cch chi tit theo tng lp: mt ct a cht-thch hc ; c im nt n , rng, mc phong ho v ph hu; cc biu hin karst ca , kch thc v hnh dng hang hc, c im lp nht; cc biu hin canxit ho, dolomit ho, thch cao ho. M t trng thi li khoan: mc dp v, ra xi, v.v..

M t khe nt phi ch ra hng (thng ng, nm ngang, nghing vi gc dc tng ng), quan h vi mt phn lp, tn s v c im khe nt (m, ng). o chiu rng vt nt, c im b mt vt nt, thnh phn, kin trc, cu to v trng thi vt liu lp nht. Nu li khoan c nh hng, tin hnh o phng v gc ca vt nt. Trong trng hp c nhiu kiu vt nt, m t tng kiu mt v nh gi c im phn b tng i ca chng. Phi c bit ch n vic m t cc hang hc v l hng ca t theo nhng s liu: su sp cn khoan, tc khoan thay i t ngt, t l li khoan, mc v c im lp nht cng nh ch ra xi, mt dung dch khoan, thay i mc nc v nhng s liu nghin cu a vt l l khoan.

M t vt liu lp hang hc karst tin hnh theo tng lp: chiu dy, thnh phn, cu to v trng thi, kch thc mnh v, mc mi mn ca chng (i vi cc sn phm a n bng c hc); hnh dng, kch thc v phn b cc tinh th v cc cht kt t (i vi cc sn phm lng xung t dung dch nc bng con ng kt ta ). Cng bng phng php , m t vt liu lp nht cho l hng, nh gi mc lp nht ca chng. Trong qu trnh khoan nht thit phi c nhng quan trc a cht thu vn: nhng khong su, m dung dch khoan lun chuyn khc nhau (lun chuyn bnh thng, mt mt phn dung dch, mt ton b dung dch); su xut hin nc ngm, quan trc s phc hi v mc nc n nh (i vi tng cha nc); mc nc n nh (tnh) i vi tng khong b mt dung dch khoan; mc nc ngm u ca v cui ca khoan; nhng khong su (a tng) nc t tro v p lc ca chng; hin tng kh thot ra t l khoan, nhit nc; ly mu nc v kh th nghim trong phng.

Trong tt c cc l khoan nghin cu karst nht thit phi tin hnh cc kho st a vt l, t nht cng phi l carota. p dng t hp cc phng php a vt l trong vic nghin cu l khoan v khong khng ln cn l khoan s cho kt qu tt nht.Tt c cc l khoan (tr cc l khoan quan trc) ngay sau khi khoan kt thc cc th nghim cn thit (carota, CTV) cn phi c loi b (trm l khoan).


18

Cc cng trnh khai o (ging, ho, rnh thm d, v.v..) cho php nghin cu mt cch y hn, so vi bin php khoan, v nt n, mc karst ho ca , thnh phn, tnh cht v trng thi ca lp ph, cc hang hc, cc i b suy yu, cc i d ti trong tng ph, nghin cu cu trc phu karst v cc loi hnh karst khc . Phng php v ni dung m t t , nt n, mc karst ho v c bn tng t nh m t trn. Trong cc cng trnh khai o cng tin hnh tt c cc th nghim hin trng CCT, CTV, VL, m c lun chng trong cng kho st. Trong mt s trng hp khi kho st phc v mt s hng mc cng trnh c bit quan trng th h o su v ho thm d l quan trng v hp l hn c.

2.8 Phng php nghin cu a cht thu vn Nghin cu CTV trong vng karst nhm gii quyt cc nhim v sau: nh gi din phn b, iu kin th nm, dy cc tng cha nc thuc tng ph, tng karst v nm di, cc thng s CTV ca chng (h s thm v.v.), mc nc, nhit , thnh phn ho hc, ch , quy lut chuyn ng ca nc ngm, iu kin cp nc v thot nc, mi quan h gia cc tng cha nc vi nc mt; nh gi nh hng ca cc yu t nhn sinh n bin i iu kin a cht thu vn v vai tr bo v ca cc tng cch nc; nh gi kh nng ho tan ca nc ngm v nc mt i vi cc karst v vai tr ca chng trong pht trin karst, st, ln cc lp v mt t. Ni dung nghin cu CTV bao gm: thu thp, phn tch v tng hp s liu a cht thu vn, iu tra CTV karst, th nghim thm, quan trc CTV, nghin cu CTV chuyn dng v thu a ho. iu tra v quan trc CTV c tin hnh theo cc quy nh chung hin hnh c ch thm v c th CTV trong vng karst. Cc th nghim thm hin trng bao gm: bm ht th , bm ht thc nghim, bm ht n, bm ht chm; p nc-p kh l khoan; nc h khoan v h o; cc phng php ch th (ho hc, ho in, so mu, ch th phng x).

Bm ht th c thc hin nhm mc ch nh gi s b tnh xng nc v tnh thm nc, la chn v tr t bm ht thc nghim v nh gi s b mc pht trin karst ca cc i khc nhau.

Bm ht thc nghim t nhng l khoan n nhm mc ch xc nh h s thm trong cc trng hp khng i hi chnh xc qu cao. Trn c s mt s lng ln cc t bm ht thc nghim t nhng l khoan n c th nh gi c c tnh thm nc ca cc i c mc pht trin karst khc nhau cng nh nhng c im chung nht v lnh th nghin cu. Bm ht chm thc nghim c tin hnh vi mc ch xc nh gi tr tnh ton ca h s thm, h s dn nc v h s x nc, mi quan h gia cc tng cha nc, mi quan h nc ngm vi nc mt. Bm ht chm trong karst nn c khng di hai tia


19

l khoan quan trc, ngoi ra vi mc ch nghin cu d hng theo phng nm ngang, mt tia b tr theo hng nt n ph bin nht, cn tia kia th vung gc vi hng . Trong trng hp nu mt l khoan trung tm khng h thp mc nc cn thit th tin hnh bm ht theo nhm (t hai l khoan tr ln). Ch khng bm ht vi thi gian di, khng nc gn nh v cng trnh trnh cc tc ng gy mt n nh.

La chn v tr l khoan v cm l khoan th nghim thm thc nghim cn phi tin hnh trn c s phn tch tnh khng ng nht v iu kin CTV theo s liu iu tra karst, khoan thm d, quan trc CTV trong khi khoan, bm ht- nc nhanh, theo kt qu carota v th nghim VL hin trng.

v p nc thc nghim : nh gi thm nc ca t khng cha nc; nh gi kh nng ht nc ca t phc v cho cng tc pht xi mng; thay th cc cng tc bm ht th. iu kin thc hin th nghim v p nc trong vng karst v c bn cng ging nh i vi trng hp bm ht.

Xc nh hng v vn tc chuyn ng ca nc ngm thc hin bng cch s dng cc cht ch th a vo l khoan v ni thu nc b mt, sau thu nc nhng im khc trong l khoan hoc ti ngun nc. Cht ch th c dng l cc cht mu (vng hunh quang, eozin, eritrozin, cng-g, xanh metilen, xanh l anilin, v.v..), cc cht ho tan (natri clorua, liti clorua, v.v..), du ho, cc ng v phng x (nu p ng cc yu cu v v sinh) v mn ca. Vic thu hi cc cht ch th thc hin bng trc quan, so mu, ho hc, in ho hc, phng x, cng nh phng php hp th cht vng hunh quang ca than hot tnh.

Trong trng hp cn thit, phi thc hin nhng th nghim CTV chuyn dng nh: quan st hin trng qu trnh ho tan ca do nc ngm v nc mt ti cc vt l t nhin v vt l nhn to v trn cc mu vt a vo l khoan, vo nhng ch xut l nc ngm ti cc h o v hang ng, cc ngun nc karst, v.v..;th nghim ngoi tri nghin cu c im ra tri v xi ngm mang vt liu ra khi ch rng v khe nt trong t ;th nghim bm pht dung dch xi mng, cc vt liu tr vo t nt n; nghin cu trong phng th nghim qu trnh ho tan trong karst v trong tng ph , qu trnh bin dng thm-trng lc trong t nm trn karst ; dng m hnh thu ng lc trn cc my tnh, cc m hnh ho tan thu ng lc ca t trn my tnh, cc tnh ton thu a c hc .

2.9 Phng php th nghim t ti hin trng

Trong vng karst c th p dng nhng phng php nghin cu hin trng: th nghim bn nn, nn thnh h khoan, ct v y trong h o, ct quay, vi xuyn,... xc nh bn v bin dng ca t tng ph nm di mng d kin ca cng trnh


20

Vi c tnh khng ng nht ca mi trng a cht trong vng karst phi s dng ti a kh nng ca xuyn ng, xuyn tnh gii quyt cc bi ton c th ca vng karst: khoanh vng cc i d ti yu v hang hc trong tng ph; khoanh vng t yu thuc cc dng a hnh karst b mt v a hnh karst trng thp; chnh xc ho mt ct a cht, trong c vic xc nh b mt cng.

2.10 Phng php th nghim trong phng v nghin cu th nghim Th nghim trong phng bao gm: xc nh thnh phn, trng thi v tnh cht c l ca ho tan v khng ho tan ca tng karst ho v tng ph; nghin cu vt liu lp nht hang hc karst v cc vt nt; xc nh thnh phn ho hc ca nc ngm, nc mt, xc nh kh nng n mn ca chng i vi cc karst. Cc nghin cu thc nghim (nu cn) bao gm: m hnh ho hc ng nghin cu qu trnh ho tan ca cacbonat; m hnh vt liu tng ng nghin cu qu trnh trng lc trn cc hang hc; m hnh thu a c hc nghin cu cc bin dng thm trng lc. Cc phng php xc nh tu ca hang hc v phu karst (nu cn): thch hc-khong vt; bo t phn hoa; kho c hc v ng v phng x.

Khi ly mu nc, phi o nhit ca n v xc nh ngay ti hin trng pH, thnh phn CO2 t do v nhng thnh phn khng bn vng khc (HCO3

-, CO32-, Fe2+, Fe3+,

NO2-, NO3

-). Cc ni dung phn tch ho hc nh gi kh nng n mn ca nc i vi karst v vn tc ho tan (Ca2+, Mg2+, Na+, K+, NH4

+, Cl-, SO42-, SiO2, hm lng

khong ho) c xc nh trong phng th nghim. Ngoi ra, cn phi xc nh nh lng trong sut, cc cht l lng, cc cht kt ta, mu, mi v.

i vi phi xc nh: t trng, m t nhin v ht m, dung trng t nhin v dung trng trng thi kh v bo ho nc, bn nn mt trc trong trng thi kh gi v bo ho nc, phi tnh ton h s ho mm, rng m v kn. Trong trung hp cn thit, phi xc nh bn ko, h s phong ho, h s n nh theo Protodiyakov, kh nng ho tan trong nc (c tnh n thnh phn ho hc v nhit nc ngm), h s v vn tc ho tan.

i vi t loi st, t loi ct, t ht th phi thc hin cc th nghim trong phng xc nh tnh cht c l ca chng bao gm: Thnh phn ht, t trng, dung trng t nhin, dung trng ca t ct 2 trng thi nn gii hn, m t nhin v ht m, cc gii hn, trng n, co ngt, tan r, gc ngh t nhin, h s thm, sc bn nn mt trc, sc chng ct, sc khng xuyn, hot tnh n mn v nhiu tnh cht khc.

Cc nghin cu thc nghim bao gm c m hnh ho dng : xc nh nh lng quy lut pht trin karst: vn tc ho tan , c ch bin dng do karst, v.v.; d bo s pht trin karst theo thi gian v khng gian di tc ng ca cc yu t t nhin v nhn sinh;


21

nh gi mc nguy him ca cc hang hc karst c khm ph; Xc nh cc thng s thit k cc bin php x l karst.

M hnh ho hc-ng dng cho nghin cu thc nghim qu trnh ho tan trong karst v t tng ph (kh kim ca mui, ho tan xi mng carbonat gn kt t mnh vn ln, v.v.).

M hnh vt liu tng ng c s dng nghin cu thc nghim cc qu trnh trng lc khc nhau din ra pha trn cc hang hc karst (gy v nt mi hang hc karst, dch chuyn trng lc t vo hang hc karst). Vt liu s dng l cc hn hp dng bt khc nhau ca cc khong vt cng c gn kt bng vazelin, du k thut, paraphin, thch cao,v.v..

M hnh thu a c hc c p dng cho nghin cu thc nghim cc bin dng thm-trng lc, xy ra trong cc t bo ho nc nm trn cc hang hc karst hoc nm trn cc ch b ph hu ca tng cch nc do karst. lp m hnh nn s dng cc mng thm, c th l vung gc, r qut hoc hnh tr.

xc nh tui hang hc v phu karst c th s dng cc nghin cu thch hc - khong vt (nghin cu cc hp th khong), cc phng php bo t- phn hoa, c sinh , kho c hc v phng x. Phn tch bo t phn hoa cc mu vt ly t cc trm tch trong hang hc hay phu karst cho php thit lp cc giai on thay i v gii thc vt xy ra t thi hnh thnh phu (vt liu lp nht hang hc karst) v xc nh tui ca n. Phng php phng x da trn vic xc nh s lng ng v phng x C14 trong cc trm tch ca phu v trong vt liu lp nht cc hang hc karst.

d on s pht trin karst trong iu kin t nhin v trong iu kin b bin i do cc yu t nhn sinh c th s dng m hnh thu ng lc trn my tnh in t . Cc nghin cu th nghim trong phng v m hnh ho phi tin hnh theo cng b sung v thng nht vi ch u t. 2.11 Phng php quan trc nh k Kho st thit k cc cng trnh ln v phc tp, k c nhng cng trnh khng ln lm nhng khi c nhu cu, phi tin hnh quan trc nh k iu kin v ng thi pht trin karst, nhng biu hin ca chng trn mt t, trong tng karst v trong tng ph. Thnh phn quan trc bao gm: ch nc ngm, nc mt, ln mt t, bin i a hnh, bin dng v h hi cng trnh.

Quan st ch nc mt v nc ngm c tin hnh khng di mt nm thu vn nhm mc ch: quy hoch vng lnh th theo iu kin pht trin karst (phn chia cc vng theo loi hnh ch nc ngm); xc nh mc karst ho, dn nc v kh


22

nng cha nc ca trong mi trng a cht; nghin cu mi quan h tng h gia cc tng nc ngm v nc mt; tnh thm t cc h cha nc, tnctn dng chy vo h mng; nh gi kh nng ngp xng nc v tnh ton cc cng trnh thot nc; xc nh s lng vt cht ho tan b mang khi khi karst qua cc khong thi gian nht nh. S liu ny cn thit kim tra nh hng nhn sinh i vi s pht trin karst v d bo pht trin karst trong tng lai c tnh n nhng yu t t nhin v yu t nhn sinh.

Quan trc ch nc ngm c tin hnh ti ngun nc, cc tuyn l khoan quan trc, cc l v ging khoan c lp, trong hang ng karst v nhiu ni khc. Quan trc phi tin hnh cho tng tng cha nc trong karst v trong tng ph, khi cn thit quan trc c nhng tng cha nc trong cc lt y. lm c iu ny cn trang b cc nhm l khoan quan trc. Ni dung quan trc ch bao gm: o mc nc, o lu lng (ngun v cc l khoan t tro), xc nh thnh phn ho hc v o nhit nc.

nghin cu ch nc mt v mi quan h gia chng vi nc ngm phi s dng cc s liu kh tng thu vn: lng ma, dng chy, bay hi, thm, nhit khng kh, v.v..;

Khi tin hnh quan st ch nc b mt v nc ngm cn s dng cc phng php a vt l. c bit l o tr sut v o nhit l phng php c hiu qu cao.Trong mt s trng hp c th phi thc hin cc th nghim th cc cht ch th nghin cu vn tc ca nc ngm vo nhng ma v nm khc nhau. Khi xy dng mng quan trc ch nc mt v nc ngm cn tnh n cc l khoan khai thc v cc cng trnh thu cng v s dng cc s liu quan trc ca chng. Trong trng hp cc s liu k trn khng th t chc quan trc thm v nh hng ca cc l khoan khai thc v cc cng trnh thu cng n ch nc.

lm r vai tr ca nc thi cng nghip v cc cht thi rn i vi pht trin karst, ti nhng ni thu gom v chn ct chng phi tin hnh mng quan trc chuyn dng bao gm: quan trc cc dng chy cng nghip (lu lng, nhit v thnh phn ho hc), cc d thng nhim nc ngm v nc mt.

Quan trc nh k cc biu hin v pht trin karst, bin dng nh v cng trnh c t chc trn c s th st karst t l 1:2000 hay ln hn, th st nh k nh v cc cng trnh, thit lp quan trc i vi cc bin dng pht hin c.So snh cc s liu quan trc bin dng theo cc mc bin dng gn trong kt cu cng trnh, cc mc su, cc mc nng cho php lm r nguyn nhn bin dng nh v cng trnh .

2.12 X l s liu Trong giai on thc a phi thc hin x l s b ti liu kim tra v m bo ti liu c cht lng v y , h thng ho v s b tng hp nhm hiu chnh kp thi


23

hng v ni dung cng vic. Trong giai on thc a phi thit lp bn ti liu thc t v bn ny c b sung lin tc trong qu trnh thc hin. Trn bn , th hin cc s liu th st trn mt t (im th st, cc biu hin karst, biu hin xut l nc v.v..), cc h khoan-khai o, cc im quan trc nh k v.v.., xy dng s b cc mt ct v bn : a vt l, a cht thch hc, a mo, a cht thu vn, mc pht trin karst b mt v di su, phn vng a cht cng trnh theo iu kin, c im v mc pht trin karst. X l ni nghip phi kt hp cc s liu thc a vi cc s liu th nghim trong phng v m hnh. Tt c s liu phi c kim tra , hiu chnh v h thng li.Trn c s phn tch v tng hp ti liu tin hnh lp bo co k thut. Bo co k thut gm phn thuyt minh, cc ph lc vn bn v th. Ni dung chi tit ca phn thuyt minh ph thuc vo mc tiu, nhim v, thnh phn, ni dung kho st ca tng giai on. 3. Kho st CCT giai on trc thit k c s 3.1 Mc tiu kho st Mc tiu kho st CCT giai on trc thit k c s l nhm nh gi iu kin CCT lnh th : la chn phng n u t xy dng cng trnh; nh gi s b tng chi ph cng trnh; d kin cc vn CCT phi nghin cu k giai on sau. (V nguyn tc vic la chn phng n u t xy dng cng trnh l do chnh quyn cc cp hoc cc c quan quy hoch ca a phng hoch nh).

3.2 Nhim v kho st

Nhim v kho st CCTgiai on trc thit k c s l lm sng t s b cc yu t iu kin CCT v hin trng pht trin karst mc chi tit nh sau:

a) Cu trc a cht: xc nh s b c im phn b, thnh phn, trng thi v th nm ca t tng ph v karst.

b) Kin to: s b v h thng t gy v bc ca chng. c) Tn kin to: s lc v cc giai on nng h tn kin to v c im lch s pht trin a cht (nu c).

d) Thu vn: c im mng sng sui v bin i lu lng, tng khong ho ca chng (nu c). e) a cht thu vn: S b phn chia cc tng cha nc trong khu vc v c im bin i ng thi nc ngm (nu c). f) a hnh - a mo: s b phn chia cc n v cu trc a mo.

g) Cc ch tiu c l t : Cc ch tiu c l ca t xc nh nh tnh bng phng php tra bng hoc ngoi suy.


24

h) Lit k s lc cc qu trnh a cht t nhin v nhn sinh khc c th xy ra trong khu vc.

V hin trng pht trin karst: phn nh s b ranh gii cc khu vc c mc pht trin karst khc nhau (phn vng karst). Lit k s b cc loi hnh karst c mt trong khu vc; lit k cc biu hin ca karst trn mt t ( cc h sp, phu, ln, ). 3.3 Ranh gii kho st Ranh gii kho st CCTgiai on trc thit k c s ph thuc vo quy m v c im tc ng ca cng trnh, ranh gii kho st CCTgiai on trc thit k c s c xc nh l ranh gii ca vng lnh th d kin tm kim phng n xy dng cng trnh trong hoc t phng n d kin la chn phng n ti u xy dng cng trnh c m rng trn c s xc nh cc yu t t nhin nh hng n qu trnh pht trin karst.

3.4 Ni dung v khi lng kho st

Cc cng tc kho st CCT giai on trc thit k c s tp trung ch yu vo thu thp, phn tch, tng hp cc ti liu c, trong c c cc ti liu nh my bay, th st CCT v x l s liu, vit bo co. Cc cng tc khc cha nn tin hnh.

3.4.1. Thu thp, phn tch, tng hp cc ti liu c:

Cn thu thp v lp danh mc cc ti liu chuyn mn c sn trong phm vi nghin cu bao gm: cc bn a hnh v mng sng sui; bn a cht chung; nh my bay (i vi cc cng trnh t cp II tr ln v khng phi l n l); Cc ti liu kho st trc (nu c): a cht cng trnh, a cht thu vn, a vt l, kh tng-thu vn.

3.4.2. o v CCT

Trn c s cc ti liu thu thp c tin hnh cng tc th st CCT, trong diu kin khng ti liu th tin hnh o v CCT t l 1: 50 000 1:25 000, tng ng vi mc chi tit kho st CCT v t l bn phn vng CCT cho giai on trc thit k c s. La chn t l o v ph thuc vo din tch khu vc nghin cu, mc phc tp ca iu kin CCT v c im ca cng trnh d kin xy dng.

o v CCT vng lnh th d kin hoc cc phng n d kin v khu vc ln cn phi c tin hnh trn nn a cht hoc thch hc-kin to c a hnh vi y cc yu t v thch hc karst, cc yu t un np chnh, ph hu kin to v cc thng s i km: bc, chiu su phn b, chiu di, chiu rng vng nh hng. Ngoi vng d kin xy dng o v CCT c tin hnh t l nh hn. o v CCT bao gm c ni dung o v thu vn cng trnh , trong cc ch tiu ho hc ca nc mt c xc nh ngay ti hin trng (cc ch tiu c th xc nh nhanh).


25

3.4.3 X l s liu, vit bo co

Theo kt qu kho st, trong giai on x l trong phng phi tin hnh nh gi s b iu kin CCT vng lnh th d kin tm kim phng n xy dng hoc cc phng n d kin, cng pht trin karst cng nh mc nguy him ca karst vi cng trnh d kin xy dng, kin ngh la chn phng n ti u xy dng cng trnh v nh hng nhng nhim v phi gii quyt giai on kho st sau (TKCS).

Tt c s liu kho st phi c kim tra , hiu chnh v h thng ho, trn c s tin hnh lp bo co k thut. Bo co k thut gm phn thuyt minh v phn ph lc.

Ni dung ca phn thuyt minh nh sau:

a) Phn m u bao gm: c s tin hnh cng vic; nhim v kho st CCT; v tr v din tch khu vc kho st ( hoc cc phng n d kin); cc thng s v cng trnh xy dng; thnh phn, khi lng, thi hn, phng php v trang thit b kho st; thnh phn nhng ngi thc hin; nhng iu chnh thay i so vi cng kho st CCT v thuyt minh cho s iu chnh . b) Phn tng quan bao gm: iu kin a l - t nhin: gii thiu nhng thng tin v a hnh, kh hu, mng sng sui, iu kin thu vn, trng thi vng lnh th; mc nghin cu iu kin t nhin: khi qut v lch s v hin trng nghin cu a cht, a cht thu vn v a cht cng trnh, kh tng thu vn ca khu vc; nh gi mc p ng yu cu nghin cu karst trong khu vc ca tt c cc ti liu thu thp c, gii thiu nhng kt qu c bn c ngha i vi vic nh gi iu kin a cht cng trnh vng lnh th; gii thiu cc thng tin v lch s khai thc, s dng vng lnh th v v kinh nghim xy dng a phng (nu c).

c) iu kin CCT khu vc nghin cu:

Trnh by v phn tch cc yu t iu kin CCT theo nhim v kho st CCT giai on trc thit k c s ( mc 3.2) bao gm: c im a mo, cu trc a cht, kin to v tn kin to, thu vn, CTV, c im pht trin karst, cc qu trnh a cht ng lc t nhin v nhn sinh.

d) nh gi iu kin a cht cng trnh: Tin hnh phn vng s b CCT lnh th theo iu kin, c im v mc pht trin karst. Trn c s chng ghp cc bn thnh phn k trn tin hnh phn vng s b CCT chung cho lnh th, nh gi-so snh cc khu vc phn chia, d bo s b bin i iu kin CCT di nh hng ca cc hot ng xy dng trn lnh th v la chn phng n xy dng cng trnh.


26

e) Kt lun: Trnh by ngn gn nhng d liu c bn v iu kin a cht cng trnh v nhng lun im c bn khuyn ngh la chn phng n xy dng cng trnh. D kin cc vn CCT phi nghin cu k giai on sau.

f) Danh mc ti liu tham kho.

Phn ph lc cn c: a) Cc bn v: bn ti liu thc t; bn a cht; bn a cht t (nu c); bn a mo; s a cht cng trnh; cc s phn vng a cht cng trnh theo iu kin, c im v mc pht trin karst; cc mt ct a cht -CCT. b) Cc biu bng: cc bng tng hp ch tiu c l t , thnh phn ho hc nc ngm v nc mt. c) Ti liu gc: bn sao cng kho st CCT; s thc a o v CCT; album nh khi o v CCT; nh my bay (nu c); cc ti liu lin quan khc (nu c). 4. Kho st CCT giai on thit k c s 4.1 Mc tiu kho st Mc tiu kho st CCT giai on thit k c s l nhm nh gi iu kin CCT : b tr s b cc hng mc cng trnh; la chn s b cc gii php thi cng, phng n gia c nn mng v x l karst; nh gi tng chi ph cng trnh; d kin cc vn CCT phi nghin cu k giai on sau.

4.2 Nhim v kho st

Nhim v kho st CCTgiai on thit k c s l lm sng t cc yu t iu kin CCT v hin trng pht trin karst mc chi tit khc nhau:

a) Cu trc a cht: i vi t tng ph: phn chia thnh cc n nguyn a cht theo mc ng nht v tui-ngun gc v thnh phn ht.

i vi gc: Phn chia theo thnh phn thch hc ( vi, olomid, macn) v c bit ch n c im kin trc v cu to ca gc ( cacbonat c xen kp thu knh hoc lp khng lin tc; cacbonat xen kp nhiu lp phicacbonat; xen k gia cacbonat v phi cacbonat; cacbonat c cu to ht th, ht nh, u ht,...).

b) Kin to: Xc nh t gy v bc ca chng, chiu di v chiu rng i c nt, tnh cht ca i c nt. c) Tn kin to: cc giai on nng h tn kin to v c im lch s pht trin a cht.

d) Thu vn: c im bin i lu lng v tng khong ho theo chiu di pht trin mng sng sui.


27

e) a cht thu vn: Quan h gia nc mt v nc ngm, mc nc v thnh phn ho hc, kh nng n mn ca nc di t, tnh thm ca t tng ph v b karst ho. f) a hnh - a mo: Phn chia chnh thc cc n v cu trc a mo.

g) Cc ch tiu c l t : Cc ch tiu phn loi t dng max- min. Cc ch tiu c l nhn c do th nghim nhanh (dung trng, t trng, m, bn nn mt trc, m un n hi, thnh phn thch hc, thnh phn ht, kh nng trng n, c im bin i t theo cc ch tiu phn loi).

h) Cc qu trnh a cht t nhin v nhn sinh khc trong khu vc

V hin trng pht trin karst: xc nh ranh gii cc khu vc c mc pht trin karst khc nhau ( phn vng karst); lit k ton b cc loi hnh karst c mt trong khu vc; lit k cc biu hin ca karst trn mt t ( cc h sp, phu, ln, ); lit k cc biu hin v tn ti karst ngm, cc i ph hu v gim ti trong karst v tng ph, c im v thnh phn cht lp nht. 4.3 Ranh gii kho st Ranh gii kho st CCTgiai on thit k c s l ranh gii ca phng n la chn xy dng cng trnh, cc tuyn giao thng nm ngoi cng trnh v c m rng trn c s xc nh cc yu t t nhin nh hng n qu trnh pht trin karst, iu kin v lch s pht trin karst, cng nh cc yu t nhn sinh lm gia tng s pht trin karst.


Cc cng tc kho st CCT giai on thit k c s c sp xp theo th t nh sau: thu thp, phn tch, tng hp cc ti liu c; o v CCT; thm d a vt l mt t; khoan - khai o; thm d a vt l l khoan; th nghim CTV; th nghim t ti hin trng; ly mu th nghim v th nghim trong phng; x l s liu, vit bo co. Trong khi lng cng vic tp trung ch yu vo: thu thp, phn tch, tng hp cc ti liu c, o v CCT, thm d a vt l mt t, cn cc cng tc khoan - khai o, th nghim CTV, VL l khoan ly mu th nghim v th nghim trong phng nn tin hnh vi khi lng hn ch.

c im ca giai on thit k c s l cng tc kho st CCT c tin hnh ch yu theo cc tuyn c trng.

4.4.1 Thu thp, phn tch, tng hp cc ti liu c:

Cn thu thp v lp danh mc cc ti liu chuyn mn c trong phm vi d n bao gm: cc bn a hnh v mng sng sui; bn a cht chung; nh my bay (i


28

vi cc cng trnh t cp II tr ln v khng phi l n l); cc ti liu kho st trc: a cht cng trnh, a cht thu vn, a vt l, kh tng-thu vn, bo co kho st CCT giai on trc TKCS (nu c).

4.4.2 o v CCT

T l o v CCT tng ng vi mc chi tit kho st CCT v t l bn phn vng CCT cho giai on thit k c s l 1: 10 000 1: 5 000. La chn t l o v ph thuc vo din tch khu vc nghin cu, mc phc tp ca iu kin CCT v c im ca cng trnh d kin xy dng.

o v CCT cho phng n la chn xy dng cng trnh v khu vc ln cn phi c tin hnh trn nn a cht hoc thch hc-kin to c a hnh vi y cc yu t v thch hc karst, cc yu t un np chnh, ph hu kin to v cc thng s i km: bc, chiu su phn b, chiu di, chiu rng vng nh hng. Ngoi vng d kin xy dng, o v CCT nn tin hnh t l nh hn.

o v CCT bao gm c ni dung o v thu vn cng trnh v c bit ch ti ni dung iu tra karst b mt.

4.4.3 Thm d a vt l

Cc phng php a vt l mt t (mt ct in, mt ct a chn ) c s dng kho st CCT giai on thit k c s nhm xc nh v khoanh vng cc khu vc nt n v karst ho mnh, cc a hnh karst trng thp, cn phng php o su in c s dng xc nh chiu su phn b ca cc vng v tm kim cc hang hc karst. Cc phng php a vt l l khoan (carota tng th, phng x l khoan, o ng knh l khoan) c tin hnh nghin cu nh lng c im nt n ca t v hang hc karst.

Cc phng php a vt l mt t c s dng c hiu qu trong iu kin chiu rng ca cc i b karst ho khng nh hn 80100m, chiu su khng qu 3040m v chiu dy tng ph khng qu 415m. Theo kt qu thm d a vt l tin hnh xy dng cc mt ct a vt l, bn d thng, phn vng khu vc theo mc pht trin karst, xc nh s b cc loi hang hc v cc loi hnh karst khc, m v tr v kch thc ca chng s c chnh xc ho cc giai on nghin cu tip theo .

Cc phng php o mt ct in, mt ct a chn c tin hnh theo cc tuyn kho st, v tr ca cc tuyn c xc nh trn c s kt qu iu tra karst b mt, t l o v CCT v chiu su d kin pht trin karst. Khong cch gia cc tuyn thay i t 25m n 100m. Cc phng php o su in c tin hnh ch yu ti cc im d thng a


29

vt l theo ti liu o mt ct in, mt ct a chn. Cc phng php a vt l l khoan phi c tin hnh tt c cc l khoan su nghin cu karst.

4.4.4 Khoan - khai o

Da vo kt qu o v CCT, kho st VL mt t cng tc khoan khai o thm d s c b tr nhm lm r thm cu trc a cht, cc hang hc karst, cc i ph hu, ly mu t v nc th nghim trong phng, th nghim CTV v VL l khoan.

Khi lng khoan khai o ti thiu c kin ngh theo bng 1:

Bng 1: T l o v CCT v khi lng khoan-khai o ti thiu trong vng karst

T l o v CCT

Tng khi lng khoan v khai o / khi lng h khoan su nghin cu karst trn 1km2 (h)

Khong cch gia cc h khoan su (trung bnh), (m)

1: 10 000 9 16 / 2 8 700 350 1: 5 000 25 50 / 8 25 350 200

Ghi ch: S lng h khoan v khong cch gia chng ph thuc vo mc phc tp ca iu kin CCT v c im ca cng trnh xy dng (cp cng trnh, c im kt cu v ti trng tc ng, cng ngh thi cng, iu kin xy dng v khai thc s dng) v s c chnh xc ho theo kt qu o a vt l. Nu cn thit th mt s h khoan cho giai on thit k c s s c trang b quan trc di hn.

Cc h khoan su trong giai on thit k c s va c chc nng thm d, va c chc nng l khoan k thut v l khoan chuyn dng.

4.4.5 Th nghim CTV

iu kin CTV c nghin cu mc chi tit tng ng vi t l kho st v o v. i vi cc cng trnh c mc quan trng khng qu cp II, d kin xy dng trn vng karst km pht trin, th mc xng nc v tnh thm ca b karst ho nt n c th xc nh theo cc du hiu gin tip ( mc nt n, mc karst ho, mc tiu hao dung dch khi khoan, ..). nh gi mc khng ng nht v tnh thm ca b karst ho theo din v chiu su, cng nh thnh phn ho hc ca nc phi tin hnh bm ht hoc nc h khoan n (th v thc nghim) theo phng php th nghim nhanh. Trong trng hp cn thit phi tin hnh th nghim trong cc h khoan CTV theo tng khong. S lng v chiu di cc khong th nghim cho mi l khoan CTV xc nh theo kt qu nghin cu


30

a vt l l khoan. S lng h khoan su c chn th nghim CTV bng 1/2 1/3 s h khoan su nghin cu karst. Trong cc th nghim CTV phi ly mu nc phn tch ho hc. 4.4.6 Th nghim t ti hin trng Th nghim t ti hin trng ch yu l xuyn ng v xuyn tnh nhm xc nh cc i l hng v d ti trong t loi ct v loi st ca tng ph. Khi lng xuyn ph thuc vo kt qu o v CCT v VL mt t.

4.4.7 Ly mu th nghim v th nghim trong phng

Ly mu t cho th nghim trong phng t tt c cc h khoan kho st bao gm: theo cc dng thch hc ca karst ho, vt liu lp nht v cc n nguyn CCT ca tng ph, mi loi mt mu th nghim / trong mt h khoan. Tng th khng nh hn 6 mu/mt n v a tng phn chia.

Mu nc ly t tt c cc tng nc ngm bt gp trong cc h khoan, cc dng chy mt, ao-h v cc dng nc xut hin khc vi khi lng nh sau:

a) Trong cc h khoan: 1 mu th nghim/1 tng. Tng th khng nh hn 3 mu / mt tng cha nc.

b) Cc dng chy mt: ly mu th nghim tt c cc v tr ca dng chy mt thay i hng chy, thay i v lu lng dng chy, thay i v iu kin a mo, mi v tr mt mu.

c) Mi ao h v cc dng nc xut hin khc ly mt mu / mt v tr, tr trng hp pht hin trong ao-h c cc d thng c bit nh mch nc nng, mch nc lnh,..th ti mi d thng ly mt mu th nghim.

4.4.8. X l s liu, vit bo co

Theo kt qu kho st trong giai on x l ni nghip phi tin hnh nh gi s b iu kin, cng pht trin karst cng nh mc nguy him ca karst vi cng trnh d kin xy dng, kin ngh s dng hp l lnh th ( trong c c kin ngh loi b cc khu vc c bit nguy him), b tr hp l cc hng mc cng trnh, la chn cc gii php x l karst, son tho c nhng nhim v phi gii quyt giai on kho st thit k k thut tip theo. Tt c s liu kho st phi c kim tra , hiu chnh v h thng ho, trn c s tin hnh lp bo co k thut. Bo co k thut gm phn thuyt minh v phn ph lc.



31

a) Phn m u bao gm: Ni dung nh mc 3.4.3 a v b sung thm tm tt cng tc kho st CCT thc hin giai on trc thit k c s (nu c). b) Phn tng quan: Ni dung nh mc 3.4.3 b trn c s b sung thm cc s liu kho st ca giai on trc


Trnh by v phn tch cc yu t iu kin CCT theo nhim v kho st CCT giai on thit k c s ( mc 4.2).

d) nh gi iu kin a cht cng trnh: Tin hnh phn vng CCT lnh th theo iu kin, c im v mc pht trin karst. e) Kt lun: Trnh by nhng lun im c bn khuyn ngh b tr s b cc hng mc cng trnh v s dng hp l, bo v lnh th, trong c nhng kt lun v nh gi, d bo karst, vic s dng cc khu vc karst pht trin mnh v nhng bin php phng chng. D kin cc vn CCT phi nghin cu k giai on sau.

f.) Danh mc ti liu tham kho. Ch : Tu thuc vo tnh cht ti liu thu c trong qu trnh kho st m c th sa i cu trc bo co. V d, phng php kho st, kt qu kho st a cht thu vn, kt qu kho st a vt l, ... c th a thnh cc phn ring.

Phn ph lc cn c: a) Cc bn v bao gm: Nh mc 3.4.3, phn ph lc b sung thm bn a hnh b mt gc; bn a hnh b mt (hoc y) v dy cc tng thch hc quan trng (nu cn); bn mc nc, thnh phn ho hc v kh nng n mn ca nc trong cc tng cha nc khc nhau; bn a cht thu vn; b) Cc biu bng bao gm: Nh mc 3.4.3, phn ph lc c) Ti liu gc bao gm: Nh mc 3.4.3, phn ph lc b sung thm danh mc cc l khoan, h o, cc im xuyn; cc ct a tng l khoan, mt ct h o, cc th xuyn; cc ti liu kho st a vt l; kt qu th nghim trong phng; mu lu ca cc l khoan. 5. Kho st CCT giai on thit k k thut 5.1 Mc tiu kho st Mc tiu kho st CCT giai on thit k k thut l nh gi y v chi tit iu kin CCT trn din tch b tr s b cc hng mc cng trnh : b tr ti u v chnh thc cc cng trnh theo mt bng ; tnh ton thit k s b nn mng cng trnh; tnh ton thit k s b x l karst; la chn loi mng hp l cho cng trnh; la chn phng php khai o hiu qu nht; d bo quy m pht trin cc qu trnh a cht nh hng


32

n iu kin xy dng v s dng cng trnh; son tho cc gii php bo v cng trnh v nn a cht khi cc qu trnh a cht nguy him. 5.2 Nhim v kho st Nhim v kho st CCTgiai on thit k k thut l lm sng t cc yu t iu kin CCT ( ti u v tng i ng u trn ton b din tch b tr s b cc hng mc cng trnh ) v hin trng pht trin karst mc chi tit nh sau: a) Cu trc a cht: i vi t tng ph: phn chia thnh cc n nguyn a cht cng trnh nh mc 4.2 v chi tit hn mc ng nht v trng thi. i vi karst: Phn chia nh mc 4.2 v b sung thm phn chia cc i theo mc nt n v pht trin karst.

i vi nm di: thnh phn khong vt v th nm.

b) Kin to: Nh mc 4.2 v b sung thm ni dung xc nh cc h thng khe nt, mt , cht lp nht trong i c nt ca cc t gy .

c) Thu vn: Nh mc 4.2, trng hp cn thit phi b sung c s liu chi tit hn d) a cht thu vn: Nh mc 4.2 nhng chi tit v chnh xc hn, b sung thm ni dung xc nh nhit v ch nc ngm, ngun cp, ngun thot, min vn ng ca nc di t. e) a hnh - a mo: Nh mc 4.2 v b sung thm ni dung xc nh cc thung lng c v thnh phn lp y ca chng.

f) Cc ch tiu c l t : Cc ch tiu c l ca t phi phn nh c tnh bin i theo khng gian, cc ch tiu phn loi phi kim tra tnh ng nht ca chng trong phm vi pht trin cc phn v t phn chia trn.

Tnh ton cc gi tr trung bnh, lch qun phng, cc ch tiu phn loi cho tt c cc n nguyn CCT ca tng ph, cc i nt n ca karst v nm di tm kim gi tr tiu chun phc v cho tnh ton s b cng trnh. V hin trng pht trin karst v nhng biu hin ca chng: Nh mc 4.2 v b sung thm ni dung xc nh: bin dng nh v cng trnh c lin quan vi karst; hnh dng, kch thc v phn b khng gian ca hang hc karst ngm, phn b cc vng nh hng v ph hu t do karst, c im v thnh phn cht lp nht. Kt qu kho st phi c s chnh xc ho phn vng a cht cng trnh khu vc xy dng theo iu kin, c im v mc pht trin karst, ng thi nh gi kh nng kch hot pht trin karst khi xy dng v s dng cng trnh, d bo pht trin karst.

5.3 Ranh gii kho st


33

Ranh gii kho st CCTgiai on thit k k thut l ranh gii b tr s b cc hng mc cng trnh c tnh n vng nh hng ca cng trnh ngoi phm vi din tch xy dng.


Cc cng tc kho st CCT giai on thit k k thut c sp xp theo th t nh sau: Thu thp, tng hp s liu; o v CCT; thm d a vt l mt t, khoan - khai o, a vt l l khoan, th nghim CCT hin trng, th nghim CTV, th nghim trong phng. Tt c cc cng vic hin trng v trong phng u c trin khai vi khi lng ln. Bt u trin khai quan trc nh k.

c im ca giai on thit k k thut l cc cng tc kho st CCT c b tr ti u v tng i ng u trong phm vi din tch b tr s b cc hng mc cng trnh sao cho theo bt k hng no cng c th xy dng c mt ct CCT v cc s tnh ton t c cc mc tiu v nhim v ca giai on thit k k thut.

5.4.1Thu thp, tng hp s liu

Thu thp ton b cc s liu, ti liu v bo co ca giai on trc, khi tng hp s liu cn c bit ch n cc biu hin karst trn b mt ( h sp, phu karst, ..), kch thc ca chng, thm ch c tui tng i, khoanh vng cc khu vc c biu hin sp, ln mi v cc khu vc ch c du vt ca cc h sp c.

5.4.2 o v CCT

o v CCT giai on thit k k thut c tin hnh t l 1:2000 1: 500 iu tra karst nm trong ni dung o v CCT v bao gm: o v ton b cc biu hin karst trn b mt t (ln, sp, khe nt) c th lin quan vi hang hc karst di su; th st hin trng ca cc nh v cng trnh ln cn, o v bin dng v l gii nguyn nhn, lm r nhng bin i cc yu t t nhin v nhn sinh nh hng n pht trin karst, c im phn b v cng pht trin karst t ln kho st trc; mi biu hin karst trn b mt u c ghi chp, o v y , c h s ring, c nh s trong h s v dng trc a xc nh to , a ln trn bn .

5.4.3 Thm d a vt l

Trong giai on thit k k thut cng tc thm d VL s dng cc phng php sau: o mt ct in khoanh nh cc khu vc nt n v pht trin karst khc nhau, pht hin hang hc karst; o su in xc nh chiu su pht trin ca hang hc karst; o su vng xc nh th nm v cu trc ca hang hc.


34

a vt l l khoan ( o lu lng nc l khoan, ng knh l khoan, phng x l khoan, carota l khoan, nhit l khoan, phng php vt th nhim in) xc nh chnh xc c im phn i nt n ca t v v tr hang hc karst.

Mng li th nghim a vt l, chng loi v kch thc thit b ph thuc vo t l o v, chiu su phn b karst cng nh tnh cht dn in v cc yu t gy nhiu. Vi t l kho st 1: 20001:500, khong cch gia cc im o su in tng ng l 25 x 25m 10 x 10m, cn khong cch gia cc im o mt ct in tng ng l 10 x10m 5 x 5m, cc im o su vng xc nh th nm v cu trc ca hang hc thng bng 30

50% cc im o su, khi lng kho st VL l khoan ph thuc vo kt qu khoan kho st v VL mt t. Khi lng l khoan thm d c ch nh th nghim VL l khoan chim 30 70% tng l khoan thm d.

5.4.4 Khoan-khai o

Khoan-khai o phi c b tr ph thuc v a hnh-a mo, mng thu vn, cu trc a cht, c im cu trc-kin to, c im phn b cc i d thng CTV, VL, c im phn b khng gian cc hang hc karst theo kt qu o v CCT v nghin cu VL. S lng l khoan su c ch nh theo bng 2.

Bng 2: T l o v CCT v khi lng khoan-khai o ti thiu trong vng karst giai on thit k k thut

T l o v CCT

Tng khi lng khoan v khai o / khi lng h khoan su nghin cu karst trn 1km2 (h)

Khong cch gia cc h khoan su (trung bnh), m

1: 2 000 100 250 / >25 (khng hn nh) 200 100 1: 1 000 300 750 / khng hn nh 100 50 1 : 500 500 1600 / khng hn nh 50 25

Chiu su ca nhng l khoan nghin cu tng ph, vt cht lp nht, khoanh vng cc loi hang hc karst, cc i gim ti trong tng ph,.. phi c lun chng trong cng nghin cu, ph thuc vo chiu su pht trin karst, kch c ca chng v chiu dy tng ph. Ngoi khoan cn phi tin hnh cc khai o b sung ( ging thm d, h o, rnh) nghin cu t trong tng ph v tin hnh cc th nghim hin trng CCT, CTV. Khi lng khai o cng phi c lun chng trong cng nghin cu v ph thuc vo khi lng th nghim hin trng khc CCT, CTV.

5.4.5 Xuyn ng, xuyn tnh v cc phng php hin trng khc


35

Phng php xuyn ng, xuyn tnh c s dng : xc nh v khoanh vng cc i d ti yu v hang hc trong tng ph; xc nh v khoanh vng t yu thuc cc dng a hnh karst b mt v a hnh karst trng thp; chnh xc ho mt ct a cht v b mt cng.

Cc phng php hin trng khc c s dng xc nh bn, bin dng ca tng ph di mng nh v cng trnh d kin xy dng (th nghim bn nn, ct v y trong h o) c b tr ti cc v tr m tng ph b ph hu v khng b ph hu do karst. Di mi mng nh mi n nguyn CCT phi tin hnh t nht 3 th nghim.

5.4.6 Th nghim CTV

Nghin cu CTV trong giai on thit k k thut phi m bo y thng tin nh gi c im CTV tng ph, tng karst v tng lt y bao gm: mc nc v gradien dng ngm, cc thng s CTV ca tng cha nc (h s thm, h s dn nc), thnh phn ho hc, nhit , kh nng n mn, ng lc nc ngm, quan h gia cc tng cha nc vi nhau v vi nc mt, kh nng bin i iu kin CTV khi xy dng v s dng cng trnh , kh nng kch hot pht trin karst. La chn cc khu vc th nghim thm, ph thuc v c im khng ng nht ca iu kin CTV, mc pht trin karst theo din v chiu su c nh gi theo cc kt qu nghin cu khc. Th nghim CTV trong giai on thit k k thut bao gm: th nghim bm ht n v th nghim bm ht cm, trong th nghim bm ht n (bao gm c nc v p nc) xc nh cc vng cha nc v dn nc khc nhau, cn th nghim bm ht cm xc nh cc thng s CTV cc tng cha nc, cc khu vc c mc pht trin karst khc nhau, mi quan h gia cc tng cha nc v vi nc mt. Khi lng th nghim bm ht n khng nh hn 3 th nghim cho mi tng cha nc karst trong mi vng c mc pht trin karst khc nhau. Khi lng th nghim bm ht cm t nht l 1 th nghim cho mi tng cha nc karst trong mi vng c mc pht trin karst khc nhau. 5.4.7.Ly mu th nghim v th nghim trong phng

Ly mu cho th nghim trong phng bao gm mu t, mu v mu nc.

Mu t c ly cho tt c cc n nguyn a cht cng trnh phn chia, mu ly cho tt c cc phn v thch hc tt c cc i nt n v pht trin karst ca tng karst v tng lt y. Mu nc ly trong l khoan khi kho st, khi th nghim CTV. Mu nc phi ly ng lot, cng thi gian, nhiu ln trong nm ph thuc vo ng thi, nhng t nht cng phi theo ma.


36

Khi lng th nghim trong phng phi c lun chng trong cng kho st cho tng n nguyn CCT v cc phn v gc b nh hng ca qu trnh karst, ph thuc vo chnh xc yu cu (xut m bo yu cu) nh gi cc ch tiu c l, mc khng ng nht ca t , cp cng trnh. Nu khng c lun chng c th th di mi mng nh v cng trnh c lp i vi mi n nguyn CCT phi th nghim khng di 10 mu ch tiu vt l v trng thi 6 mu ch tiu c hc. Mu nc th nghim ly t mi tng t nht 3 mu (mi ma) xc nh thnh phn ho hc, kh nng n mn ca nc di t.

5.4.8 Quan trc nh k

Cng tc quan trc nm trong ni dung kho st CCT xy dng cc cng trnh ln v phc tp, k c cc cng trnh khng ln lm nhng c nhu cu pht hin cc biu hin mi ca karst, cng nh nghin cu ng lc pht trin cc loi hnh karst pht hin , chu k quan st ph thuc vo mc pht trin karst v tm quan trng ca cng trnh xy dng.

Quan trc ng lc nc di t c tin hnh trong cc ging, cc tuyn h khoan, cc h khoan n l, cc ngun xut l nc . Mng v khi lng quan trc c lun chng trong cng kho st v ph thuc vo iu kin a cht, CTV khu vc xy dng, cng nh cc yu t tc ng nhn sinh t cc ngun khc nhau nh: cc cng trnh khai thc nc ngm, cc cng trnh thu cng, cc cng trnh x l, chn lp cht thi. Hng nm phi theo di nh k trng thi ca nh v cng trnh trong khu vc kho st v quan trc nh k cc cng trnh b ln, bin dng. i vi cc cng trnh nguy hi cho mi trng, cn phi xy dng h thng quan trc karst, trong bao gm c cc quan trc nh k VL, bin dng nn mng cng trnh, mc nc v thnh phn ho hc ca nc di t.

5.4.9 X l s liu, vit bo co. Tt c s liu kho st phi c kim tra , hiu chnh v h thng ho, trn c s tin hnh lp bo co k thut. Bo co k thut phi m bo y s liu giI quyt cc mc tiu t ra mc 5.1 v bao gm 2 phn: thuyt minh v ph lc.


a) Phn m u: Ni dung nh mc 4.4.8a; b) Phn tng quan: Ni dung nh mc 4.4.8b;


Trnh by v phn tch cc yu t iu kin CCT theo nhim v kho st CCT giai on thit k k thut ( mc 5.2 ).


37

d) nh gi iu kin a cht cng trnh:

nh gi - d bo quy lut (kh nng v cng ) pht trin karst; nh gi hin trng bin dng b mt t v pht trin karst ngm khu vc d kin xy dng; phn vng karst theo iu kin, c im, mc pht trin karst; nh gi mc n nh khu vc d kin xy dng do karst; trn c s ca nhng kt qu kho st, trong bo co kho st phi c kin ngh cc gii php phng chng karst (kt cu, iu chnh nh hng tc ng ca nc, chng thm, gia c nn mng, cc gii php cng ngh v khai thc). e) Kt lun: Trnh by nhng lun im c bn khuyn ngh b tr chnh thc cng trnh v s dng hp l, bo v lnh th, trong c nhng kt lun v nh gi, d bo karst, nhng bin php x l karst. D kin cc vn CCT phi nghin cu k giai on sau.

f) Danh mc ti liu tham kho. Ch : Tu thuc vo tnh cht ti liu thu c trong qu trnh kho st m c th sa i cu trc bo co cho ph hp. Phn ph lc cn c: a) Cc bn v: Ni dung nh mc 4.4.8, phn ph lc v b sung thm bn karst b mt t v karst ngm ; bn a cht cng trnh ct lp ti cc su khc nhau (nu cn). b) Cc biu bng: Ni dung nh mc 4.4.8, phn ph lc. c) Ti liu gc: Ni dung nh mc 4.4.8, phn ph lc v b sung thm danh mc cc biu hin karst trn mt t - st, ln, phu v.v; danh mc cc biu hin karst ngm. 6. Kho st CCT giai on thit k bn v thi cng

6.1. Mc tiu kho st

Mc tiu kho st CCT giai on bn v thi cng l chnh xc, chi tit ho v nh gi iu kin CCT tng khu vc xy dng cng trnh (trong phm vi tng vng nh hng ca cc hng mc cng trnh) tng ng vi kin trc v phng php thi cng thit k sao cho cc thng tin CCT cn v : hon thin ton b tnh ton chnh xc cho cc hng mc cng trnh v nn mng ca chng; hon thin cc thit k c bit; son tho phng n thi cng cng trnh; thit k thi cng bin php x l karst.

Cn ch rng tt c cc yu t CCTquan trng quyt nh iu kin xy dng cng trnh nht thit phi c nh gi nh lng.

6.2 Nhim v kho st


38

Nhim v kho st CCT giai on bn v thi cng l chnh xc ho v chi tit ho cc yu t iu kin CCT v hin trng pht trin karst trong phm vi vng nh hng d kin ca cc hng mc cng trnh bao gm:

a) Cu trc a cht: i vi t tng ph: nh mc 5.2 hoc phn chia theo cc gi tr tnh ton; i vi karst: nh mc 5.2; i vi nm di: thnh phn khong vt, th nm v bn ca .

b) Kin to: Nh mc 5.2 .

c) Thu vn: Nh mc 5.2, nhng s liu phi c c trng theo ma. d) a cht thu vn: Nh mc 5.2

f) Cc ch tiu c l t : Nh mc 5.2 v b sung thm yu cu cc ch tiu bin dng, bn xc nh bng cc phng php hin trng l ch yu.

V hin trng pht trin karst v nhng biu hin ca chng: Nh mc 5.2 v b sung thm ni dung d bo nh hng ca cc yu t nhn sinh n pht trin karst trn mt v di su

Trn c s cc ti liu k trn chi tit ho v hiu chnh vic nh gi mc v c im pht trin karst, iu kin pht trin karst, kh nng kch hot nhn sinh pht trin karst, kh nng n nh ca cc khu vc xy dng tng hng mc cng trnh c lp.

6.3 Ranh gii kho st

Ranh gii kho st CCTgiai on thit k bn v thi cng l ranh gii ca vng nh hng d kin ca tng hng mc cng trnh c lp.


Cc cng tc kho st CCT giai on thit k bn v thi cng ch b tr b sung di h thng mng ca cng trnh d kin bao gm: khoan - khai o v thm d a vt l chim t trng ln trong khi lng kho st; xuyn ng - xuyn tnh v th nghim hin trng khc cng nh cc th nghim trong phng, th nghim CTV c trin khai vi khi lng nh hn; quan trc nh k c tip tc trong giai on ny; x l s liu, vit bo co.

6.4.1 Khoan - khai o

Cng tc khoan trong giai on thit k bn v thi cng nhm xc nh s bin i mt ct CCT, iu kin CTV, chnh xc li kch thc, hnh dng hang hc karst, kim tra cc d thng VL v nghin cu nh lng-chi tit cc biu hin karst trn mt t trong


39

phm vi vng nh hng d kin ca tng hng mc cng trnh c lp, trong trng hp cn thit c th phi khoan c ngoi phm vi thit k ca nh v cng trnh.

S lng h khoan trong phm vi cc nh v cng trnh ph thuc vo tm quan trng v kch thc ca nh v cng trnh, cng nh iu kin, c im, mc pht trin karst. Khong cch gia cc h khoan c chp nhn trong khong 20 50m . Trong khu vc phn b cng v na cng su khng ln (di 20m), di nn nh v cng trnh cp quan trng ( cp I-.II) cn phi tin hnh khoan-khai o chi tit hn, khong cch gia cc h khoan l 10-20m v nh hn, ng thi cng phi khoan trc tip di cc mng ring bit ti khu vc pht trin karst mnh nh gi chnh xc kh nng n nh ca din tch xy dng. Cc h khoan phi cm su vo cng-phong ho nh khng di 12m. Nu chiu dy tng ph v tng karst ln hn 30 50 m, chiu su ca cc h khoan phi c lun chng ring trong cng kho st. Di nn nh v cng trnh c tm quan trng cp I-II, 1/3 s h khoan kho st phi cm vo tng phong ho nh 5m. Chiu su ca cc h khoan cn li c tnh ton theo yu cu kho st cho cc trng hp kho st thng thng khc. 6.4.2 Thm d a vt l

Trong giai on thit k bn v thi cng s dng ch yu phng php o su in v cc phng php a vt l l khoan nhm khoanh nh chnh xc phm vi phn b cc i nt n, cc hang hc karst. Trong tt c cc l khoan su u phi s dng cc phng php VL l khoan (o lu lng nc l khoan, ng knh l khoan, phng x l khoan, carota l khoan, chiu in v chiu m gia cc l khoan) .

6.4.3 Xuyn ng - xuyn tnh v cc th nghim hin trng khc

Cng tc th nghim hin trng trong giai on bn v thi cng c b sung khoanh vng cc i xung yu- d ti trong t dnh v b ri tng ph di mng cng trnh v xc nh cc ch tiu bn v bin dng ca chng khi cn thit. Cc phng php th nghim bao gm: xuyn ng, xuyn tnh ct cnh, nn thnh h khoan, nn v ct, y trong h o. Khi lng th nghim c lun chng trong cng kho st.

6.4.4 Nghin cu CTV

Nghin cu CTV trong giai on thit k bn v thi cng c b sung chnh xc ho cc thng s CTV (mc nc, gradien dng thm, h s thm, h s dn nc, thnh phn ho hc, nhit , kh nng n mn, ng lc nc ngm, quan h gia cc tng cha nc vi nhau v vi nc mt) cho d bo bin i iu kin CTV v gii quyt cc bi ton thit k h thng h thp mc nc, thit k cc gii php chng thm.


40

Th nghim CTV trong giai on thit k bn v thi cng ch yu th nghim bm ht cm c b tr trong phm vi h mng v trc tip ti cc v tr thit k h thng chng thm, h thng h thp mc nc, h thng thot nc, . Khi lng th nghim bm ht cm t nht l 1 th nghim cho mi tng cha nc karst trong mi vng c mc pht trin karst khc nhau (c tnh n th nghim ca giai on trc). 6.4.5 Ly mu th nghim, th nghim trong phng v nghin cu th nghim

Ly mu cho th nghim trong phng bao gm mu t, mu v mu nc t cc h khoan v h o.

Th nghim cc ch tiu c l ca t c tin hnh cho tt c cc n nguyn a cht cng trnh phn chia trong phm vi tng cng trnh c lp hoc nhm cng trnh. S lng th nghim ti u ( xc nh cc gi tr tiu chun v cc gi tr tnh ton) phi c tnh ton v lun chng c th trong cng kho st, ph thuc vo mc khng ng nht ca t , chnh xc yu cu (xut m bo yu cu) th nghim, cp cng trnh xy dng. Trong trng hp khng c d liu tnh ton khi lng th nghim ti u th di mi mng ca cng trnh c lp i vi mi n nguyn CCT phi th nghim khng di 10 mu ch tiu vt l v trng thi, 6 mu ch tiu c hc (k c cc mu th nghim giai on trc). Mu nc th nghim ly t mi tng t nht 3 mu (mi ma) xc nh thnh phn ho hc, kh nng n mn ca nc di t.

Trong giai on bn v thi cng nu xt thy cn thit c th tin hnh cc nghin cu th nghim trong phng v m hnh ho phi theo cng b sung v c ch u t chp thun.

6.4.6 Quan trc nh k

Quan trc nh k bt u t giai on kho st trc, phi c tip tc giai on thit k bn v thi cng. Li v ni dung quan trc c th c hiu chnh theo kt qu nghin cu thc t.

6.4.7 X l s liu, vit bo co

Tt c cc s liu kho st hin trng, th nghim trong phng, nghin cu th nghim, quan trc nh k phi c x l-phn tch v h thng ho, m bo y s liu gii quyt cc mc tiu t ra mc 6.1. Bo co k thut bao gm 2 phn: thuyt minh v ph lc.


a) Phn m u: Ni dung nh mc 5.4.9 a;

b) Phn tng quan: Ni dung nh mc 5.4.9 a;


41


Trnh by v phn tch cc yu t iu kin CCT v hin trng pht trin karst theo nhim v kho st CCT giai on thit k k thut ( mc 6.2 )

d) nh gi iu kin a cht cng trnh:

nh gi - d bo b sung quy lut (kh nng v cng ) pht trin karst(nu cn thit); nh gi b sung hin trng bin dng b mt t v pht trin karst ngm khu vc d kin xy dng (nu cn thit); nh gi b sung mc n nh ca din tch d kin xy dng do karst (chnh xc ho); trn c s ca nhng kt qu kho st, trong bo co kho st phi c kin ngh chnh thc v cc gii php x l karst, kin ngh v cc ni dung quan trc tip theo (nu cn thit). e) Kt lun: Trnh by ngn gn nhng lun im c bn khuyn ngh chnh thc v thit k nn mng cng trnh v x l karst. D kin cc ni dung quan trc giai on xy dng v s dng cng trnh (nu cn thit).

f) Danh mc ti liu tham kho. Ch : Tu thuc vo tnh cht ti liu thu c trong qu trnh kho st m c th sa i cu trc bo co cho ph hp.

Phn ph lc cn c: a) Cc bn v: Ni dung nh mc 5.4.9, phn ph lc; b) Cc biu bng: Ni dung nh mc 5.4.9, phn ph lc ; c) Ti liu gc: Ni dung nh mc 5.4.9, phn ph lc;


42

Ph lc A (tham kho)

nh gi iu kin a cht cng trnh trong vng karst

A1 Phn vng a cht cng trnh lnh th theo iu kin, mc v c im pht trin karst. A1.1 Trn c s ca nhng kt qu kho st c th phn vng lnh th karst theo cng pht trin cc h sp mt t v ng knh trung bnh ca cc h sp (bng A1, A2). Bng A1 - Phn vng lnh th pht trin karst theo cng pht trin cc h sp mt t

Phm tr n nh lnh th pht trin karst Cng pht trin cc h sp mt t (h/km2.nm)

Vng I Vng II Vng III vng IV Vng V Vng VI

Trn 1.0 T 0.1 n 1.0 T 0.05 n 0.1 T 0.01 n 0.05 Nh hn 0.01 Khng c kh nng sp mt t do karst

Bng A.2 Phn vng lnh th pht trin karst theo ng knh trung bnh ca cc h sp mt t

Phm tr n nh lnh th pht trin karst ng knh trung bnh ca cc h sp, m A B C

ln hn 20 t 10 n 20 t 3 n 10 nh hn 3

A1.2 Phn vng a cht cng trnh l c s nh gi vng lnh th pht trin karst phc v xy dng. Cc kt qu phn vng gip cho cc n v thit k xc nh mc ph hp


43

A1.3 Cc yu cu i vi phn vng c xc nh bng t l ca n, ng thi ph thuc vo cc iu kin t nhin v nhu cu c th ca bi ton thit k. T l phn vng c la chn thuc vo giai on thit k.

A1.4 Phn vng c m t trn bn t l chn, t l ny xc nh cc thang bc phn chia lnh th (vng, khonh, ..) v chi tit phn chia .

A1.5 Phn vng c thc hin : a) Theo iu kin pht trin karst, c tnh n cc iu kin xut hin chng trn mt t; b) Theo mc v c im pht trin karst, bao gm c mc v c im xut hin karst trn mt t. Phn chia cc vng, khu, khonh v.v.. c tin hnh theo cch xp chng bn mc v c im pht trin karst ln trn bn iu kin pht trin ca n, i chiu v kt hp chng. Cn ch rng cc ranh gii pht trin karst khng phi lc no cng trng khp vi cc ranh gii a cht v a mo, nhiu khi s pht trin karst tin st n cc ranh gii . A1.6. C s c bn ca phn vng l phn tch lch s a cht v iu kin pht trin karst. C bn iu kin nh vy ( mc 1.4.1). Ngoi ra, phn vng theo iu kin pht trin karst cn phi lu cc iu kin pht trin xi ngm, dch chuyn v sp l ca t cng nh cc qu trnh khc tham gia vo s hnh thnh hang hc, cc i b ph hu v d ti trong cc karst v tng ph, ng thi cng phi lu ti s hnh thnh cc h sp v ln b mt t.

A1.7. Trong phn vng cn nghin cu v s dng cc quy lut pht trin karst. Quy lut c phn loi thnh: quy lut chung, quy lut khu vc v quy lut a phng cc cp khc nhau.

A1.8. Nhng quy lut chung quan trng nht cn tnh n trong phn vng l: a. S pht trin tch cc ca karst trong cc ho tan din ra cc i c s trao i nc tch cc; b. s pht trin karst c xc nh bi ton b lch s pht trin ca n trong qu kh, hin ti v tng lai. Trong , rt ra c mt lot cc quy lut chung khc nh: mc pht trin karst gim theo su (vi cc iu kin khc l tng ng); karst pht trin mnh hn gn thung lng v gim dn theo hng n ng phn thu; karst pht trin v phn b trong cc i nt n mnh, i ph hu kin to, di mc n mn c s.


44

A1.9. phn vng theo iu kin pht trin karst, nn lp b bn vi mt t l thch hp: cc bn a cht, cu trc-kin to, a mo, v a cht thu vn (bao gm c thu a ho ).

A1.10. phn vng trc ht phi phn chia ranh gii lnh th cc kiu karst theo thnh phn thch hc v c im th nm. Mun vy, trc ht phi phn chia v khoanh vng cc thnh h cha cc ho tan c xt n tui ca chng, phn chia cc khu vc nng, h, cc i ph hu kin to, cc i nt n mnh, cc khu vc c dy v thm nc tng ph khc nhau, cc yu t cu trc a hnh-a mo (b mt san bng, sn dc thung lng, thm v.v..) v cui cng l cc khu vc c ch thu ng lc khc nhau v cng trao i nc trong cc karst khc nhau. Phn chia cc thi k pht trin karst. Ni dung nh trn l phn vng lnh th theo iu kin pht trin karst t l 1:50 000 - 1:25 000. Phn vng t l ln hn phi phn chia t m hn na. Phn b ca cc thnh h cha ho tan thng c khng ch bi cc cu trc kin to cc cp bc khc nhau.

A1.11. Trn bn phn vng t l 1:50 0001:25000, lnh th nghin cu c chia thnh cc vng: khng pht trin karst, pht trin karst mnh, trung bnh v yu. Vng khng pht trin karst l vng khng c t ho tan, hoc b ph bi t khng thm nc, khng ho tan tng i dy. cc khu vc ng bng, ni pht trin karst thng lin quan cht ch vi s pht trin a hnh v mng sng ngi, bi v mng sng ngi v a hnh -a mo lin quan trc tip vi cu trc kin to cc bc khc nhau, cc i ph hu, nt n mnh.

A1.12. Mi vng hoc khu c phn chia trong bn phn vng t l 1: 50 000 1: 25 000 phi c ch gii y v: loi karst, iu kin a cht, a mo, a cht thu vn cng vi cc mt ct tng ng, mc v c im pht trin karst, c im biu hin karst trn b mt t. Mc pht trin karst v n nh lnh th cho php c nh gi nh tnh hoc nh tnh na nh lng trn c s tng t a cht.

A1.13. phn vng t l 1:10 000 v ln hn, i vi mi tng trm tch v mi tng a cht thu vn nn thnh lp ring cc b bn bao gm: a hnh b mt v chiu dy ca tng, ranh gii ca cc loi (tng ), c tnh thm, mc nc, thnh phn ho hc, c tnh n mn ca nc. Thnh lp cc bn cu trc kin to, a mo, bn pht trin karst ngm v trn mt, cc mt ct CCT, CTV. Trn c s phn tch cc ti liu phn chia lnh th nghin cu thnh cc khu vc theo iu kin, mc v c im pht trin karst. Phn vng theo iu kin pht trin karst c tin hnh da trn nhng du hiu sau (xem thm mc A1.10):


45

a) Phn b cc tng trm tch ca karst, tui, dy, cu trc, thnh phn v cc tnh cht c-l ca chng. b) Phn b ca cc tng trm tch ca lp ph, tui, dy, cu trc, thnh phn, tnh thm nc cng nh cc tnh cht c-l khc ca chng. c) iu kin th nm ca karst v tng ph, cu trc kin to v cc i yu, a hnh karst c trng su tui khc nhau. d) Cc yu t a mo (thm sng, sn dc thung lng, b mt phn thu c tui v cu to khc nhau. e) iu kin a cht thu vn pht trin karst v cc biu hin ca n trn mt t. Phn vng theo mc v c im karst tin hnh theo ch dn cc mc A2.1 A2.22 v A5.1 A5.14 . nh gi mc pht trin karst b mt v n nh ca lnh th cc t l 1:10 000 v ln hn phi l nh lng theo mc A6.1 A6.29. Khi phn vng cn xt n quy lut phn b v pht trin karst. Ngoi nhng quy lut ch ra mc A1.8, nn ch thm mt s im sau: karst thng pht trin nhng ni m thm nc b mt tng i d dng, nhng ni m tng cch nc b vt mng to nn cc ca s thu vn (nc tng nm trn xung cc tng nm di), hoc sn cc thung lng. Karst nhiu khi pht trin nhng thm sng, sun dc ca cc thung lng c cng nh phn cn li cu cc ho tan , theo cc i tuyn tnh ph hu kin to v nt n mnh v c bit l vi cc ch giao nhau ca chng.

A1.14.Phng php vi phn vng, chnh xc v chi tit ho ( cc t l ln hn 1:2000) phng php nh gi mc pht trin karst v mc n nh cc khu vc xy dng cc to nh v cng trnh ring bit c cp n phn sau (cc mc A7.1 A7.21). A1.15. Trong phn vng a cht cng trnh v d bo n nh lnh th nn p dng phng php nh lng nh gi nh hng ca cc yu t t nhin n vic pht trin karst v cng to cc h st karst, trong nn s dng cc phng php phn tch tng quan nhiu chiu. A2. nh gi trng thi ca t v cc biu hin ca karst ngm A2.1 nh gi trng thi ca t v cc biu hin karst ngm cn thit xc nh kh nng n nh ca lnh th nghin cu v cc khu t xy dng cc nh v cng trnh c lp, ng thi cng tnh ton nn mng, nh gi iu kin a cht thu vn xy dng v khai thc s dng cng trnh, d bo kh nng v hot tnh pht trin karst trong tng lai, thit k cc bin pht chng karst .

A2.2 Kt qu kho st phi m bo nh gi v mc nt n, rng v cc tnh cht c-l khc ca t v mc pht trin karst .


46

A2.3 Cc biu hin ca karst ngm bao gm: cc khe nt m rng do ho tan karst; cc l rng do ho tan; cc loi hang hc karst; cc i b ph hu v d ti; b mt ho tan ca mi, nn v sn cc lp hoc thu knh karst; cc ph hu th nm t do dch chuyn v st t bn trn cc hang hc karst, trn cc i b ph hu v d ti; cc phu

tcxdvn 366-2004 công tác khảo sát Địa chât cho công trình vùng kaster

Documents