DliN DAN KHOA HOC C 6 N G NGHE
MOT SO VAN DE VE KY T H U A T N E N MONG VUNG DAT DOC
(Tiep theo)
PGS.TS.NGUYEN BA KE
Hpi Cd hgc Ddt va Dja Ky thugt cong trinh Xay dt^ng Vigt Nam
IV. Mpt so' giai phap phong chong triidt
Theo [1] mpt so'gidi phdp phdng chdng trUdt mdi/sUdn dd'c dUdc tdng hdp va trinh bay trong bang 1.
Bang 1- Cac giai phdp phdng chd'ng trUdt mdi doc
PtufOng phap Lo^i ra n muc Olch dilnh
(phong ngiia hG|c cilli chita)
a) Jtay da linh dang ciia na doit Gidin dOcao
Gidin dfi nghieng
Them trgng lupng ci chSn dtlic (phan ^ )
Khi tupt n a y Cho lit ca d£l/da Oft
Phdng n gia Air lysfim Phong n gia/XL/lyscin Xtrlysflm
bjIQansoatn/ecm^
Phu tham thuc vdt Bit cac nut ne HSMnglhodtnufic
Oft O f V d i
oarvdi
Phdng ngia
Phong ngia Air lyscm Phdng ngia Air lysfim c)iaan soM stf A a n / i t f ngSm
Gifng 1hu nJx, sdu
Dufing float nufic difig Irpng luc OuQng lio^t nu6c ngang nhlSu iSng HSm, hao thoat nuQc
Gi^ng giam ap hoac ranh <3 chSn d5c Du^g hao thu nuQc
Oem tiSu n\tc Dien M m Hoa hpc
OakhS Oft/iti
zism.
Oa/ dSft rin chic 03ft
OSt-Dao/iSp ort (phu len) Oft (phu sa) ort(seti
Xirly 1am thai Phong ngia Air lyscm
Phdng n gia ^ ly sfm ngay tir dSu Phdng ngifi/xirlyscm
Xirlyscim
Phdng ngia/XLTly sdm Phdng ngia
Phdng ngiQ/xiriy sdm Phdng ngifl/)£rlyscm d) Chong gn
Be da bang be Ifing Ch8t(&
Oai be Ifing va chft d i Neo bing cdp LuGJphii
Phun phu mat bing be £ng Tri^tufingfipdi
Titig bing rQ da TufingdJi
Tudig chin bing Be t n g cftlhep T i n g chin bing be Ung co neo Tuttig Irpng kic bing di hodc be Ifing Cpc khoan nhS hoac cpc r l cdy
Da CD mai dua ra
ChS niit ne hcdc chS da bl tach Niit ne ldn hoac di. mSm ySu Od nghiSng theo via ChS da d5c
Da y^u mfm hcac d £ da niit ne Oft citig/ (ti mim
O f t c i i i g / d i m l m Dft tuong dSi ciing Dft/di hlSn hop Dft/klihSnhap OftAli Dft/itihSnhgp
Phdng nqia.
Phdng ngie/xirlylrupt Phdng ngia
Phdng ngiQ/XL/ly sdm Bao giijf da khdng bi rd Phdng ngib
Phdng ngCa Airly sdm Phdng ngia Air lysitn Phdng ngia
Phdng ngia
Ridng ngia xir ly ngay d ttidi gian dfu Phdng ngia
Phdng ngia/xirly sdm
Cdc giai phdp phdng chdng trUdt mdi dd'c sUdn ddi Id nham gidm hoac chd'ng sat Id; chung phai dUdc chpn dClng phu hdp vdi dieu kien da't dd cu the vd tren cd sd tinh todn can than. Vi vay nhifng thdng tin ve dia chat cong trinh va dia chat thuy van cd y
nghia cUc ky quan trpng. Mat khdc cdc gidi phap dd (phdng ngUa bode cdu chiia) cung phai dUdc thUc thi mpt cdch kip thdi va cang sdm cang td't, vi neu khong thi khdng the lam dUdc. Vi du: khi dao neu khdng neo/ chan ngay thi da't dd bi yeu di do mUa
NGlTdl X A Y Dl/NG S6 THANG 10 - 2009
nang chang han, mai sau mdi neo chan thi khdnp cdn cho da't tdt de dat neo nila hoac phai dat neo rat sau va se ra't tdn kem.
Kiem sodt nUdc mat de loai trir hoac ban che sU tha'm ciia nudc vao sUdn/ mdi ddc vi dieu dd se gay ra xdi ngam, njfa troi da't d xung quanh bode da't d chan ddc va din den sU sat Id da't.
Can ndi rd them ve cdc bien phdp phdng chd'ng cdu chiia trUdt vij'a trinh bay d bangl.
a. Bien phdp thay ddi hinh dgng mdi ddc ThUc cha't ciia phUdng phdp nay la nham giam tai trpng hoac dp dd'c cua mdi da't
Dao da't d doan trUdt chinh cua mdi trUdt, de giam trpng lUdng da't phan tren khdi trUdt giam lUc trUdt xudng, khien cho khdi da't dUdc can bang.
PhUdng phdp nay phan ldn la phdi hdp ciing sii dung vdi cdc bien phdp khac. Chi khi doan mdi trUdt ma phia tren dUng dUng phia dUdi thoai, vach phia sau trUdt va khdi da't d hai ben tUdng ddi dn dinh mdi cd the su* dung phUdng phdp nay, neu khdng, cd the lam cho pham vi trUdt md rpng, lam cho sU cd trUdt vdch sau va khdi da't d hai ben them xau hdn.Tren hinh 1 la vi du cho trUdng hdp vUa neu.
M6T S 6 VAN DE VE KY THUAT NEN MONG...
Phuang phdp hinh hgc
Cat giam dO cao Lam doc thoai lirin
I'hiicfngphdp hinh hoc
D^nh bdc ho$c xen diu d i p clian doc
Hinh 1: Phdng trugt bang cdch gidm do cao, do ddc, ddnh bdc, ddp chdn (phan dp)
b) Bien phdp tieu thodt nUdc
Bien phdp tieu thodt nUdc bao gdm thodt nUdc mat vd nudc ngam. Nudc mat d ngoai khoi ddc trUdt, la'y ngdn ddng vd dan ddng sang chd khdc lam nguyen tac; nUdc mat ben trong khd'i trUdt, nguyen tac la chdng tha'm va dan ra ngoai. Ddi vdi doan trUdt mai dd'c ma nUdc ngam tUdng ddi manh, nUdc mat tha'm tUdng dd'i nghiem trpng, phai bo' tri cdc trang bi thoat nUdc ngam nhU ranh ngam; neu ben dudi cd ldp tha'm nUdc manh, cd the bd tri nhieu id ddng de thodt nUdc (xem hinh 2 va 3).
c) Bien phdp bdo ve mdi ddc
Ddi vdi cac vet nUt va da't tdi xdp tren be mat
Uififii;; lifii lh();it m « c n«M\«, "J,,- lieu niTdc bang bom hiil
Hinh 2: Tieu thodt nudc dudi ddt bdng he thdng ngang va diing
Hinh 3-Tieu thodt nUdc mat theo nguy ca trugt khdi trUdt, phai tien hanh dap bit vet nUt vd dam chat. Tren mat ddc trdng cay, trdng cd (hinh 4), xay da phie^n, bdo ve mat bang each phii be tdn^ ... deu cd tac dung bao ve mai ddc. Tai day cdn can diing cac bien phap bao ve mdi, kiem tra dinh ky va thudng xuyen sijfa chiJa bdo dUdng ..
Hinh 4: Chia 6, trdi ddt mau, gieo co
Co Vetiver cd tac dung bao ve taluy nen dat, chong xdi mon be mat hdn cac loai cay khdc chinh la nhd cd bp re phat trien. Bp re co Vetiver phdt trien theo dang r l chiim an sau vao trong da't, co nhiTng ndi chi sau kbi trdng 4 de'n 6 thang, chieu sau bp r l da phat trien khoang 2m t p thanh he ludi lam cot cho da't cd tac dung lien ket cac ldp da't vd hat da't.
Sau khi trdng 4 den 6 thang, cd Vetiver se cai thien cdc chi tieu cd, ly, hod da't trdng mpt cdch dang ke, giO" cdc hat da't khong bi riia troi.
Sii dung cdc bang cd Vetiver vuong gdc vdi hudng ddng chay se gidm van td'c cdc tac nhan bao mdn be mat nhU nUdc, gid, ban che xdi mdn, kiem sodt viec troi da't va giS da't bi riia trdi lai phia tren NGl/dl XAY Dl/NG S6 THANG 10 - 2009
M6T S 6 VAN OE VE KY THUAT NEN MONO...
hang rao co, dn dinh che dp thuy nhiet, gii? dp am cho da't, tao dieu kien cho cac thUc vat khac phdt trien^phii xanh toan bp mai dd'c.
O nhifng sUdn dd'c cd da bi phong hda nhieu hoac de bie'n cha't (nUt ne, trUdng nd, mem yeu) do tdc dpng ciia khi hau khi bi Id ra ngoai, de bao ve chiing can lam ldp phii bang be tdng hoac diing hod chat tao mang chd'ng tha'm tren be mat mai dd'c vi du nhu san pha'm "Soil - Master" ciia My. Day la loai cao phan tii d the long cd mau trang nhU sii'a, khdng dpc hai, khong bi pha hdng ca'u triic do tia cUc tim ciia mat trdi tac dpng, khdng gay chay nd. Be day ldp phii tir 1mm den 10mm, sau 60 - 75 phut da hinh thanh mang chd'ng tha'm yeu cau. (hinh 5).
Hinh 5: Cai ludi thep len be mat dd vd bOm phii be tong hoac chdt deo
d) Bien phdp chdng giQ
Dd la bien phdp xay dUng ket ca'u chd'ng trUdt, lam cho khdi da't trd lai can bang. Ket ca'u chd'ng trUdt thudng diing cd hai loai: tUdng chan chong trUdt vd cpc chd'ng trUdt. Trong cdng trinh d viing niii diing tudng chan dat kieu trpng lUc tUdng ddi nhieu, cd Uu diem la vat lieu lay d dia phUdng, ky thuat thi cong ddn gian (hinh 6). Cpc chdng trUdt phan ldn la cpc be tdng cot thep kieu ddo / khoan Id, kieu gieng chim, cung cd khi dCing cpc re cay (hinh 7).
NhCing giai phdp bao ve va cUu chCa trUdt Id mdi ddc trong nganh giao thdng cd rat nhieu, trong dd cd nhieu gidi phdp ddn gian kha phii hdp vdi dieu kien mien nui (xem tdi lieu [2]).
Tudng chan chd'ng trUdt mdi ddc la bien phdp dUdc xem xet dau tien, thudng diing d trUdng hdp
Hinh 6: Sa dd cdu tgo tudng chdn ddt chdng trugt
1. Dd gdc tdt
2. Ap luc cha dgng ciia ddt 3. Ddp ddt set ddm chat
4. Ldp cdch nudc
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3
4
Hinh 7- Ket cdu cong trinh chdng trugt bang cgc L Cdu kien chdng trugt; 2. Ddi cgc bdng BTCT;
3. Tudng chdn; 4. Thanh/ddm chdng bang BTCT;
5. Mat trugt tinh todn 6. Ddt lap lai sau tudng;
7. Ddt cua ldp trugt (d set, sdi san, vun ndt cua set iiet);
8. Ddt on dinh dphia dUdi mat tritgt (set, cuoi, sdi, set ket, dd vdi...).
chii dpng phdng ngii'a trUdt, ddt d chan dd'c hoac d tren mai doc nham gidm dpng ndng khi da't dd rdi trUdt tU tren cao xuo'ng phia chan dd'c.
Trong rat nhieu trUdng hdp lUc day cua mdi trUdt len tudng chan (lUc gay trUdt) ldn hdn rat nhieu so vdi dp life da't thiet ke cua tudng chan da't cho mdi ddc thdng thudng. Do dd mat cat ciia tudng tUdng ddi ldn, hinh thUe ca'u tao cua nd nhU trinh bay tren hinh ^6.
O day chi gidi thieu, qua vi du thUc te, nhUng giai phap phdng ngifa hoac chd'ng sat Id cho cong trinh dan dung, cdng nghiep la chinh. DUdng nhien khdng the tdch rdi hai linh vUc ndi tren vi chiing cd ciing muc dich va cd the rut kinh nghiem lan nhau.
Vi du 1: Su cd' trUdt 6 tinh Sdn Tay(Trung Quo'c) [3] da diing bien phdp tdng hdp de xiir ly: ke^t ca'u chdng trUdt giam tai va thoat nUdc.
Khdi quatsU cd
Dat tUdng dd'i day thupc ky thU tU, ldp tren cd nhieu da dam da tang, dp rdng tUdng ddi ldn, trong miia mUa phan ldn nUdc mUa theo cac khe niJt tha'm vdo ldp biin ben dUdi. Do ben dudi cd ldp da't set tUdng dd'i chat va ldp thd nbudng cd khdng tha'm nUdc, vi vay hinh thanh ddng chay cua nUdc ngam.
Hdn nffa, khi thi cong nhd xUdng d dudi chan ddc da
NGl/dl X A Y Dl/NG sd THANG 10 - 2009
dao cat chan dd'c nen lam cho khd'i da't tren dd'c trUdt theo mat khdng tha'm nUdc.
Xl? ly siC cd
Mai trUdt nay thupc loai trUdt keo theo, siia chffa tong hdp lay chdng giff lam chinh ket hdp giam tai va thodt nUdc nhU trinh bay tren hinh 8.
- Dd ddt gidm tai trgng: tai cot cao 1,664m va 1,656m bd' tri cac cd mdi, tai 2 cd nay ha mdi dd'c xudng 28°, tdng lUdng da't dao bd di la 30.000m' de giam tai len mdi dd'c. Qua tinh todn lUc gay trUdt cdn 292IkN, diing cpc chd'ng trUdt va tUdng chan de chdng giff theo tffng cap.
- Ranh cat nUdc vd rank thodt nUdc: phia ngoai khdi trUdt xay ranh cat nUdc hinh khuyen trdn, ngdn nUdc mat ciia dd'c niii chung quanh, ddng thdi d dinh ddc ciia cd tai cdt cao 1.664m xay ranh cat nUdc bang dd phien, thdng vdi ranh cat nUdc d phia ngoai khdi trUdt de thodt nUdc mat ben trong khd'i trUdt.
M6T S6 VAN DE VE KY THUAT NFM MONG...
't _ i l 6 2 0 . V
•n
Uanh c3t mUlc
Cao d(> i6A4ni Cao dO 16S6m
MSI tri/(;t
M^t da ga^ )604.S
Coc fho'nf; i.Tiiifi
Ti/(fng ch^n d^t
Hinh 8- Tinh Kinh siia chita mdi ddc ciia vi du 1 1. Ranh cdt nudc;
2.DUng 19 cay cgc chdng trugt;
3. Tudng chdn ddt chdng trugt ddi I25m,cao 8m giap
vdi dudng hdm sd 2;
4. Kho;
5. Tudng chdn xay phdng;
6.Dudng ndi vdi ranh nudc cUa nhd mdy.
- Bd tri cpc chdng trUdt va tUdng chan da't chdng trUdt; tai cdt cao 1.624m. Diing cpc be tdng cdt thep cd tiet dien 1,7x1,9m, dail8~25m, dao bang thii cdng. Mui cpc deu ngam vao ldp da't dn dinh phia dudi mat trUdt, ta't ca cd 19 cay cpc de chdng lai lUc gay trUdt 2.356 kN.
- Tai chan mai ddc d cd't cao 1.633m bd tri tUdng chan da't chdng trUdt dai 125m, cao 8m chiu lUc da'y
(luc gay trUdt) 565,5kN.
- Cud'i ciing can tien hanh tu chinh, chen lap cdc khe nfft, cdc Id khoan dd'i vdi khd'i trUdt.
Vi du 2: Khu du lich Xdtri ndi tieng cua Nga vdi mat dp dudng giao thdng day ddc, hang nam thudng xay ra sat Id tdi 3-4 lan [4]. Qua nhieu dieu tra nhUng van khdng biet dUdc quy luat sat Id vi no xay ra ba't cU liic ndo: sau khi mUa to, sau khi tuyet rdi va ca khi thdi tie't kho rao. Diing da ddm dap chffa chd trUdt va trai nhUa nhUng chi dn dinh trong thdi gian ngan rdi sau dd lai sut Id nhU trUdc. Phia bd sdng Maseta da't trdi tao nhieu nep nhU sdng. TrUdt da bat dau day cac be dd dUdng o'ng va xua't hien cac ve't nfft trong than be va xd lech khoang cdch giffa cdc be. TrUdt cung da de doa ngoi nha ciia vien dieu dudng nam d phia tren dd .
Nguyen nhdn sU co vd cdch xu: ly
Nam 1976 Vien thiet ke chuyen ngdnh Ucraina (Ucrspestroiproekt) de nghi dung cpc khoan nhdi lam ket ca'u chd'ng trUdt. Da't d sUdn dd'c nay la deluvi ky thff tU (a set vd set ndng cd dam san vd cdc manh cat ke^t) nam tren nham gdc - argilit cd cdc ldp cdt ket. Chieu day ldp trUdt trung binh 6-9m. MUc nUdc ngam cd dp nam d dp sau tren l,5-9m tiep xuc vdi ldp deluvi va da goc.
Trong khi khao sdt vet trUdt cd chieu ddi de'n 270m, rpng 100 -150m. Mat trUdt d phan giffa co gdc nghieng 10-12° so vdi phUdng ngang vd men theo dia hinh.Tff do ta tha'y rang trUdt chii yeu Id do ca'u triic dia chat ciia sUdn dd'c, cdc bien phdp chdng trUdt ndng khdc nhau khong the dn dinh dUdc sUdn ddc nay. Cd mpt so' phUdng an dUa ra xem xet nhU gia cUdng sUdn dd'c bang be phan dp va tUdng chan cd sUdn nghieng nhung cdc pbUdng an nay khong dffng dUdc vi d chan dd'c la be dd dUdng dng va bd sdng cung nhU do mat trUdt d kha sau.
Tai day da dung ket ca'u chd'ng trUdt sau ddt thanh 2 day (hinh 9). Ket ca'u chdng trUdt dUdc tinh vdi luc gay trUdt 300-500 kN (tuy theo vj tri cua ket ca'u va mat cat ngang tinh todn theo chieu dai sUdn ddc). Ap lUc gay trUdt xae dinh theo tai lieu khao sat dia chat cong trinh ve cdc ddc trUng ben lay tai mat trUdt: gdc ma sat trong ^=9-15° lUc dinh c=0,15- 0,4 MPa.
Hinh 9:Ket cdu chdng trugt sau cho vi du 2
1-Tudng chdn dd xay dung; 2 ,3-Ket cdu chdng trugt dphia tren vd phia dudi; 4-Ddt ddp; 5-Argilit vd alevrolit; 6-Coc khoan nhoi
(Xem tiep trang 44)
NGl/dl XAY Dl/NG S6 THANG 10 - 2009
