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8/9/2019 bo co i cht

1/23

a cht mi trng Nhm 2

Phn m u.-Lch s loi ngi chng kin v phi chu bao thm ho au bun v

trt l t trn sn dc, mi dc.-Vo ngy 20 thng 9 nm 1884, ti vng Xa-ra-tp ngi ta thy mt t

rung chuyn mnh nh ng t, hn 300 ngi nh cng cng trnh xy dng nh

nh my, cng xng, nh th b nghing nga v sp xung.- Lin X c, vo nm 1946 mt b m thuc cng trng khai thc l

thin m than Bgoxlv pht sinh mt khi trt. Ban u, trt mi xy ra trnmt khu vc ca b m ko di theo sn 650m, xui theo b n 250m; sau kch thc khi trt tng ln n 900m theo ng phng v 360m theo hngdc. Mt trt ct su n 25m, th tch thn trt t 5,6 triu m3. Trt xy ra saukhi di chuyn din khai thc vi tc khng ng u nhng khu vc khc nhau.

- Vit Nam, hin tng trt cng rt ph bin nht l vo ma ma, vthng xy ra mnh nhng vng ni Ty Bc v thng ngun Sng Chy, vngni Trng Sn v vng ng Bc. Hng nm Ty Bc cc v trt l xy ra

thng xuyn, c bit trn cc tuyn quc l 6, quc l 8... gy ch tc giao thngnghim trng. Nm 1992 ti bn Nm Tong, Lo Cai xy ra mt khi trt ln tini tip xc gia cc xm nhp granitoid khi Ye Yn Sun v bin cht htng Sinh Quyn c ng knh hn 100m, su 20-25m. Nm 1993, mt khi trtkhc vi th tch hng trm ngn m3 chn ngang dng sui Ngi Bo, gy ngplt cho khu vc xung quanh v phi mt nhiu ngy mi khai thng c dngchy. Thng 6 nm 1996, ti m Apatit Cam ng, xy ra trt khi t t cao 300m trt xung lm cht 6 ngi trong mt gia nh v lp kn nhiu ao h.

Trt t l mt dng tai bin ca t nhin,n l mt mi nguy him ng sca con ngi.

Trt t cng vi cc hin tng lin quan ca n gy thit hi rt ln chocuc sng ca con ngi.Mi nm, c 25 ngi b mt mng do l t Mv con s ny tng ln khong 100-150 ngi nu chng ta tnh lun cnhng hm m b sp.Con s thit hi c tnh trn 1 t la.

chng ny chng ta cng tho lun v s sp ln,mt dng thm ha linquan n trt t,cc vt liu tri t b r ra theo chiu thng ng thngto ra nhng h trn mt t nhng cng gy ra nhng dng tn tht khngtheo quyA.Trt t

I.Khi qut chu ng1.Khi nim.-Trt t l s dch chuyn trn b mt hay gn b mt ca mt khi t

theo chiu trng lc (t cao xung thp), p lc thu ng, lc a chn v mt slc khc, cc quy m khc nhau: quy m nh khi trt l c th ch vi m3 quym ln khi trt n hng nghn m3 t .Khi khi trt dch chuyn,tn tht sxy ra trn khi trt v c ni dn t vt liu trt.(a cht mi trng.)

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2/23

a cht mi trng Nhm 2

- Trt t l hin tng di chuyn cc khi t trn sn dc theo mtmt trt no . Khi t b trt gi l thn khi trt. Chiu rng ca thnkhi trt c th ti hng trm mt, th tch c khi ti hng vn mt khi hoc hn.c im hnh thi ni bt ca ca mt khi trt l n cn gi c tnh nguynkhi hoc c th b rn nt, nhng cha n mc v ra. Do tc dng ca trng lc

v lc ma st, nh v chn khi trt thng b bin dng cht t. Tuy nhin, trnb mt khi trt, cy ci vn tn ti v pht trin, nhng thn cy c th b uncong hoc xiu vo nn c gi l "rng say". y c coi l du hiu quan trng d bo trt t sp xy ra mt ni no t.(on kho st a cht mintrung)

Th d:-Trt t b sng Tn Chu a mt phn ch Tn Chu,v c quan

UBND huyn xung sng v dch chuyn trong 2.-Trt l thng 11nm 1972 thung lng sng Ritxuela-ty Gruzia lm dch

chuyn khi t l 3 triu m3 lp y mt on sng di 350-450m2.Nguyn nhn ca trt t.(nguyn nhn gin tp)*Nguyn nhn t nhin:

-S xi mn ca cc dng sng.-S tan chy ca cc dng sng bng.-L lt,cc trn ma ln lm l cc lp t .-Nhng trn ng t.-S phun trao ca ni la.-S dch chuyn ca cc mch nc ngm.

*Nguyn nhn do con ngi:-Nhng chn ng t cc hot ng xy dng-Giao thng v cc cng trnh ng x.-Cc chn ng t cc v n.-Cc hot ng khai thc m di lng t.-Vic ph hoi cc cnh rng.

3.Cu trc khi trt-Mt trt: l b mt trn khi trt dch chuyn.Mt trt c th dng

phng hay cong, dc ca mt trt c th thay i.

-Vch trt : cn gi l vt sp nh du mc dch chuyn ca khitrttheo chiu thng ng,s lng vt trt nh du s ln di chuyn ca khitrt.

-Khe nt ngang: y l cc khe nt phn b pha trn khi trt,l du hiuv s hnh thnh mt khi trt.Trn mt t cc khe nt ngang c dng vngcung,mt lm hng v khi trt. m ca cc khe v mt khe nt l ch thv nguy c dch chuyn.

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3/23

a cht mi trng Nhm 2

-Khe nt dc: l cc khe nt thng ng phn b ngay trn b mt khitrt,phng ko di song song vi dch chuyn.y l khe nt pht trin khi khitrt dch chuyn;chng ph hy ni b khi trt,kt qu lm cn kit khitrt,c bit l cc khi trt di chuyn xa v din bin lu di.

-i vt liu di chuyn-i cn kit: cn gi l i trt.Khi t b di

chuyn do tc dch chuyn khng ng iu gi cc b phn ca khi c bit lphn trn mt v v phn y,vt liu trong khi s chu tc dng ng thi ca ccyu t khc nhau,kt qu cu trc vt liu b ph hng dn n s ph hy bn trongni b khi dc theo ng vn chuyn.

-i dn t l ni tp trung cc vt liu trt t trn xung.4.Sn dc v n nh trn sn dc4.1 Khi nim.-Sn dc l mt dng t ph bin nht trn tri t,chng l nhng h

thng khng tnh lng.

-Vt cht trn cc sn dc hu ht dch chuyn n nh trn sn dc theotc a dng.S dch chuyn ca lp t rt nh m ta kh c th nhn bitc n s l t hon ton d di.Nhng qu trnh ny l mt l do chnh dn nnhng dng sui trn i tr nn rng hn rt nhiu.

4.2 Qa trnh hnh thnh cc sn dc.4.2.1 S hnh thnh dc.

Vic xc nh thnh phn ca con dc l cn thit.Bi v n l mt phn quantrng quyt nh s dch chuyn ca cc vt liu.Con dc c bn thnh phn chnh:

+nh dc.

+Dc .+Phn dc nghing t 300 n 350.+Vng dc lm thp hn.

Tt c nhng con dc c cu to bi mt hay nhiu yu t ny v s hnhthnh cc sn dc c lin quan n cc yu t ny.

-Phn nh dc lin quan n s dch chuyn chm ri ca khi t .-Phn vch th thng lin quan n n qu trnh ri.-Phn dc nghing t 300 n 350 l ni m phn vch hi t.Gc nghing

ca phn ny l phn gc nghing n nh nht m loi vt cht c th duy tr tnh

nh ca mnh trn .-Phn dc li c to nn bi qu trnh lin quan n nc chy4.2.1 S n nh ca dc- bit c nguyn nhn ca trt t,chng ta phi xem xet n nh

ca dc.y l vn c th c din t kha cnh trn lc ca dc.Lc nyc xc nh bi mi tng quan ln nhau ca loi hnh: vt cht ca tri t,dcnghing ca dc,kh hu,thc vt,nc v thi gian.

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4/23

a cht mi trng Nhm 2

- n nh ca dc m t mi lin h gia driving force,lc khin vt chtdich chuyn xung dc v lc cn tr di chuyn.Lc di chuyn ph bin nht lthnh phn khi lng ca vt cht bao gm bt k th g trn dc.Lc cn tr dichuyn ph bin nht l mnh ca vt cht.

- n nh ca dc c tnh bi SF,ngha l t s gia lc cn tr di

chuyn v lc di chuyn.+Nu SF>1(lc cn > lc di chuyn) dc c xem l n nh.+Nu SF


5/23

a cht mi trng Nhm 2

*Hai yu t nh hng n phng thc dch chuyn khi trt.:-Hnh thi mt trt: l yu t quyt nh kiu dch chuyn.

+Mt trt phng quy nh kiu trt tnh tin.+Mt trt cong quy nh kiu trt xon hay cn gi l trt ngu

lc. - dc mt trt l yu t chnh quyt nh vn tc dch chuyn.5.4.S bin v.-Vn tc dch chuyn.-Kiu dch chuyn.-Vt liu cu to khi trt.-Khong cch dch chuynII.Vai tr ca cc kiu vt liu trn tri t.-Vt cht xung mt dc nh hng kiu hnh v tn s ca s chuyn

ng xung di.S trt xung c hai mu c bn ca s chuyn ng l quayvng v tn tin.

-Loi t l nguyn nhn ca c vic ri v trt ca cc vt liu.-Cng vt liu dc c th gy nh hng ln n tn s ca nhng vng

trt t1.Vai tr ca dc v a hnh-Dc nghing ln nh hng ln lc trt trn mt dc.-Qa trnh tng gc ca mt trt dn n ng lc cng tng.2.Vai tr ca kh hu v thc vt

*Kh hu hay thc vt c th nh hng n st l t hay s di chuynxung di trn mt dc no

*Vai tr ca kh hu l kim sot c thin nhin,phm vi lng ma vlng hi m ca nhng vt liu trn .

*Vai tr ca thc vt trong vng trt t kh phc tp bi v cy c trongvng l vi chc nng ca cc nhn t,n lm nh hng trn cc sn dc.Thc vtl nhn t quan trng trn cc sn dc l v:

-Thc vt l mt mn chn hn ch lung ma ri trn cc nh dc,toiu kin thun li cho s thm nc vo t.

-Thc vt c h r to ra s kt dnh cc vt liu trn cc sn dc.-Thc vt thm trng lng vo dc.3.Vai tr ca nc-Nc hu nh trc tip hay gin tip ko theo vic l t , v th m n rt

quan trng . Nhiu s phong ha ha hc ca nc lm bin i cng s trt l1 cch chm chp l nguyn nhn gy ra bi cc hot ng ha hc ca nc trongvic tip xc vi t gn b mt tri t

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6/23

a cht mi trng Nhm 2

-Nc c kh nng tc ng xi mn n n nh ca sn dc rt nhiu .Cc t v ng xi mn c th lm di chuyn vt liu v lm cho sn dc , v thlm gim bt h s an ton

-Nc c th lm gim n nh ca ch dc (*) lm gim nhanh chngmc nc trong h cha hoc sng ( t tc ti thiu 1m/ngy )

-Nc cng gy ra trt l v n gp phn lm xy ra s ha lng ca trmtch giu t st , hoc hin tng ha lng (*) trong sut nm 1964 ng t tora nhng tc ng ny v n rt tn ph

4.Vai tr ca thi gian-Kh nng chng chi ca sn dc thng thay i theo thi gian-Sn dc c th t bn vng theo thi gian v c th tng tc ca s l

cho ti khi (*) h s an ton ca chn dc cng c th gim theo thi gian v tnhtrng m t nhanh chng l nguyn nhn gy ra s xo trn ca mnh vn t sn dc.

III.Phn loi trt t.-Phn loi c im vn ng ca khi trt.-Phn loi chuyn ng trt.-Phn loi trt l theo thnh phn vt liu-Phn loi trt theo vn tc chuyn dng.-Phn loi trt theo m ca vt

1.Phn loi theo c im vn ng.- Trt tri: Khi trt bt u chuyn ng t pha chn ri lan dn v pha

nh. Kiu trt ny lm cho khi trt tri theo mt sn v pha chn dc.

- Trt y: Chuyn ng trt bt u t nh ri do sc ysinh ra ttrng lc ca phn trn khi trt m cc b phn bn di phi vn ng theo v

pha chn sn. Do lc ma st gia thn khi trt v khi gc rt ln nn kiutrt y ny thng xut hin g bin dng rt c trng ti chn khi trt.

2.Phn loi chuyn ng trt.1.1.Trt.-S dch chuyn ca khi t trn mt b mt-mt trt.-Hnh dng mt trt to thnh cc kiu trt sau:

+Trt xoay.

+Trt tnh tin.+Trt ngang.

1.1.1 Trt xoay.-Khi trt di chuyn trn mt trt cong.-Vn tc di chuyn trung bnh ca khi trt t trung bnh n nhanh.1.1.2Trt tnh tin

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7/23

a cht mi trng Nhm 2

-Mt trt phng,c gc nghing nh,i khi phn bc.-Khi mt trt cc khi nghing nh s di chuyn rt chm,nhiu lc kh

quan st trc tip m thng qua cc mc quan trc hay thng qua cc du hiu trnb mt.

1.1.3 Trt ngangS dch chuyn ngang ca khi nn l kt qu ca s ha lng hay ha do

hoc do s gia tng th tch ca mt b phn khi nn1.2.B,trn.-S dch chuyn ny ng vai tr quan trng.-S dch chuyn ny ch nhn bit qua cng tc quan trc.-Vn tc dch chuyn gim dn t trn xung di.-Yu t nh hng ti s dch chuyn ny l yu t mi trng1.3.Chy.

-Vt liu vn chuyn lin tc c s bin dng bn trong ni b khi trt.-Chuyn ng ny thng xut hin trn sau nhng cn ma ln1.4.L,ri,sp .Mt trt dc ng,vt liu ri t do hay chuyn ng xoay quanh mt tr c

nh gn y trt.3.Phn loi trt theo thnh phn vt liu.

Kiu dchchuyn.

gc Vt liu gn kt yu.

Ht th. Ht mn.

nho,l ,l.

vn ,vn l.

t ,t l.

Trt.Trt xoay.Trt tnh tin.Trt ngang.

sp./khi

trt. chui.

vn sp. vn/khi

vn sp. vn

chui.

t sp.Khi t/t

trt.t chui.

Chy. Chy . Chy vn. Chy t.

Phc hp. Phi hp t hai kiu c bn.

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8/23

a cht mi trng Nhm 2

4.Phn loi trt theo vn tc dch chuyn.

Vn tc dch chuyn.

Chm. Trung bnh. Nhanh.

1mm/nm-mm/ngy. cm/ngy-cm/giy. >100km/gi.

Quy m. Nh-trungbnh.

Trung bnh:100-104m3

Trung bnh-rt ln.

100-104m3.

Vt liu nn. t(chyu), gc(thn).

gc vt( cc t l khcnhau).

Ch yu l gc, khnggn kt hay b

phong ha.

Kiu dichuyn.

Chy,phngt,dch chuynngang.

Chy trt. Trt chyv ri.

Tn gi. Chy. Trtxoay,chy t,trt vn.

Tuytl,dng vn,dng bn,.

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9/23

a cht mi trng Nhm 2

5.Phn loi theo m ca vt liu.

- 9 -

SngDng

vn.

Dng bn Chui t

Dng t Trt l vn.

t ChyDng bng .

Tuyt lTrn

l

Chy.

Tng mTng m

Tng mTrt/. Dch chuyn ngang.


10/23

a cht mi trng Nhm 2

IV.Cc iu kin dn n hin tng trt t.-Hin tng trt t xy ra ph bin nhiu ni, nhng n ch xy ra trong

nhng iu kin nht nh, khi c tnh trng mt cn bng v trng lc. Trng thiny thng xy ra khi lp v phong ho dy, vt cht trn sn dc b thm mnc, chn sn b ht hng, vn ng kin to v cu trc a cht thun li... C

th l:- Nhng ni c lng ma ln v tp trung vi cng cao th nc ma s

thm vo t lm tng trng lng ca tng trn mt v khi t n b mt tngkhng thm nc s gy nn hin tng xi ngm. Nu tng khng thm nc l stth khi b thm nc, n s tr nn rt trn v d gy ra trt t.

- Nu trn b mt sn dc c h thng t gy kin to pht trin s lm chot vn nt, c nhiu khe nt, to iu kin cho nc thm xung lm gim lckhng ct ca t , t nguy c pht sinh trt t cng cao hn.

- iu kin v cu trc v th nm ca c nh hng rt ln n qu trnh

trt t. Khi cc tng c th nm cm v pha thung lng, tc l nghing theochiu dc ca sn th trt t d xy ra hn.- a hnh cao, dc v chia ct ngang ln s to ra nng lng a hnh

ln, l iu kin thun li cho cc qu trnh trt t c ngun gc trng lc. Vnng kin to hin i v cc trn ng t cng gy nn cc tai bin trt l cngsinh.

- Qu trnh trt t cn chu nh hng ca cc tc ng nhn sinh nh: ctxn chn dc khi lm ng giao thng, xy dng cc cng trnh c ti trng lntrn sn dc, khai thc m bng phng php n mn, hot ng ca cc phngtin c gii...

V.C ch ca trt t.1.Mc n nh sn v kh nng trt t.1.1 Xc dnh s n nh ca sn dc.-Vic xc nh nguyn nhn gy ra trt t cc sn dc l cng vic rtkh khn. Trong thc t, hu ht cc trng hp trt l u do nhiu nguynnhn gy ra v him khi ch do mt nguyn nhn duy nht. Xc nh nguynnhn gy ra trt t chnh l tm ra cc yu t tc ng gy ph hy s nnh sn dc. Quan h gia tng cc lc chng li s di chuyn khi t (S) v tng cc lc gy trt (T) c T.V. Zvonkova [6] gi l h s nnh (K) v c xc nh theo cng thc:

K = S / T (1)-Sn v t hnh thnh sn s trong trng thi n nh nu K > 1, khim S > T. Khi K = 1, tc l S = T th sn nm trong trng thi cn

bng gii hn. Nu K < 1, tc l S < T th sn trong trng thi khng nnh.

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11/23

a cht mi trng Nhm 2

Khi phn tch cc lc tc ng ln mt khi nm trn sn dc,th gc dc ng vai tr quan trng trong vic thit lp t s ban u cacc lc chng trt v gy trt.

Ghi ch: : Gc dc ca mt trt; P: Trng lng khi ; T: Lc tip

tuyn c xu th lm cho khi di chuyn xung sn dc (cn gi l lc gy trt)v = P.sin; N: Lc php tuyn v = P.cos; S: Lc ma st c xu th gi khi litrn sn dc. Lc ma st c quan h vi lc php tuyn thng qua h s ma st (f)v c th hin theo cng thc: S = N.f = P.cos.tg (vi f = tg v l gc ma

st trong ca t ).-T cng thc (1) c th vit

-ng vi mt loi t th c mt gi tr gc ma st trong xc nh, nn khi

thay i dc ca sn th h s n nh s thay i theo. trng thi cn bnggii hn K = 1, th ta c: = . Do , khi < th sn s n nh.-Trn c s m hnh s a hnh, bn dc, bn t v bn thc vt cngvi cc dn liu u vo khc, bn n nh sn tnh Qung Bnh cthnh lp di s tr gip ca phn mm Sinmap chy trong mi trng Arcview[5]. Din tch v t l ca cc cp n nh c trnh by Bng 1.-Qua Bng 1 ta thy din tch sn c mc khng n nh chim hn 25% a

phn tnh Qung Bnh v tp trung vng i ni, ni c tuyn ng H Ch Minhi qua. Do , phc v cho cng tc duy tu, bo dng v cnh bo ch tc giaothng vo ma ma l, ng thi phc v cho cng tc quy hoch cc im dn c

v pht trin sn xut c hiu qu, cc vng c tim nng trt l cn phi cnghin cu mt cch y .

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12/23

a cht mi trng Nhm 2

Bng 1: Thng k din tch v t l n nh sn tnh Qung Bnh.(Ngun:Vin a l).

TT Mc n nh Din tch (km2) T l (%)

1 Rt n nh 4.598,26 58,9

2 n nh 441,88 5,6

3 Tng i nnh

755,06 9,7

4 Khng n nh 2.014,74 25,8

1.2 Quy lut phn b cc im trt.*Trt t xy ra do nhiu yu t tc ng nh: a cht, a hnh, a mo, kh hu,lp ph thc vt v hot ng ca con ngi [2]. V vy, vic tm ra quy lut phn

b cc im trt l rt kh khn, nhng v cng cn thit. Trn c s kho st thca, kt hp vi vic phn tch mi quan h ca cc vt trt vi cc yu t t nhinv nhn to, bc u c th rt ra mt s quy lut nh sau:

-S lng cc im trt t t l thun vi cao v dc a hnh.

- B dy lp v phong ho cng ln th kh nng trt t cng cao- Thnh phn ca khc nhau th kh nng xy ra trt l cng khc nhau2.Nguyn nhn gy trt.(nguyn nhn trc tp).-Do s tng tc ca sn:

+S xm thc t nhin ca cc dng chy hoc gi.+Do chuyn ng nng nn lin quan n chuyn ng nng vm tn kin

to hoc do bin ng ca ca p lc thy tnh.+Do hot ng o bi ca con ngi khi khai thc cc ti nguyn.

-S gim bn ca t .

+Tng hm lng nc.+Thay i thnh phn ha hc ca vt liu nn.+S suy gim cht-gia tng l hng ca lp t .

-Pht trin hin tng t bin trong khi nn.+S gia tng p sut l hng.+S gia tng ti trng sn.

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13/23

a cht mi trng Nhm 2

+Mt i s chng pha bn di. 3.C ch ca trt t.

-C ch pht trin ca mt khi trt l c s t chc gim st s dch chuynvxc nh cc bin php gim thiu tai bin ca trt t.

-ng lc pht trin ca mt khi trt chia lm ba thi k:+Thi k chun b.+Thi k hot ng trt thc th.+Thi k n nh.

3 .1 Thi k chun b.-L giai an pht trin cc iu kinl gim n nhca khi trt.-Thi k ny biu hin bng s suy gim h s n nh sn.-Thi k chun b c th ko di hay din tin nhanh chng ty theo hon cnh cth.

-Thi k ny kt thc khi c s xut hin nhng vt nt trn khi trt.3 .2 Thi k hot ng trt thc th.-Thi k ny cc hot ng dch chuyn mnh m gy nn cc vt nt cng ln dn.-H s nh ca ca sn dc gim v chuyn sang ngng chuyn ng.2.3.Thi k n nh-y l thi k cc hot ng ca khi nn t n s cn bng, l lc cc nhn tgy trt b loi b hon ton.-Du hiu nhn bit y l a hnh tng i bng phng,khng cn cc khe nttrn mt.

VI.Tai bin trt t v cc hot ng ca con ngi.-Tc ng ca vic s dng v nh hng ca con ngi n cng v tn sutxut hin trt t gn nh t nh n ln.-Nhiu s trt l c gy ra bi nhng nh hng ln nhau gia cc iu kin acht tri ngc , vt qu hi m , v cc thay i nhn to trong cnh quan v vtliu sn ni.1.Vn nn cht ph rng ca con ngi

-Rng hoc thm thc vt c tc dng gi li nc ma, bo v t chng lixi mn v ngn nga c l lt. Vic cht ph rng vi quy m ln s to ra cc

vng t trng v c th to nn tng lng nc chy xung cc dng sng suiln hn, nhng vi tnh bin thin cao hn v hu qu l xi mn t vng thnglu v bi lp di h lu. ng thi, cc khu rng cng l mt yu t sng cntrong h sinh thi t nhin, l ni duy tr cc khu h ng thc vt phong ph v lmt nhn t ch yu quyt nh ti nguyn nc. Vic cht ph rng cng ng thilm mt cn bng sinh thi v mt cn bng nc ti vng h lu.

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14/23

a cht mi trng Nhm 2

-c tnh, tng din tch rng t nhin trong khu vc khong 585 triu ha.Khong 2,5 triu ha rng t nhin hng nm b cht ph trong thp k qua. Khuvc chu Thi Bnh Dng phi tri qua nhiu mt mt do chy rng v cht

ph rng bt hp php.2.Cc tn tht do tai bin gy ra.

-Trt l t c xem l mt tai bin nghim trng c nh hng trc tipn s pht trin kinh t,x hi ca cng ng.

-Trt t gy ra cho ngi nhiu tn tht nng v ngi v ca:+Tn tht v sinh mng.+Tn tht v kinh t.

2.1 Tn tht v ngi.

STT S kin S ngi thit

mng

Ni xy ra Thi gian

1 Loess flow 180,000 China 1920

2 Debrisavalanche

70,000 Peru 1970

3 Mudflow 23,000 Columbia 1975

4 Debrisavalanche

12,00020,000

SovietUnion(present-day

Russia)

1949

5 Debrisavalanche 18,000 Peru 1970

6 Debris flow 10,000 Columbia 1999

7 Lahar 5,110 Indonesia 1919

8 Rock avalanche

4,000 Peru 1962

9 Rock slide 2,000 Italia 1963

10 Debris flow 1,000 Ecuador 1987

Mt s thit hi ca l t nc ta.Ngy 30/6/2003 trt t - xy ra ti bn Chu Va 12, huyn Tam ng, tnh LaiChu lm cht mt nam v lm b thng nng mt n du khch ngi M. Mi ymt trn trt t kinh hong xy ra vo m 13/9/2004 ti x Phn Ngan, huyn BtXt, tnh Lo Cai lm cht 23 ngi.2.2 Tn tht v kinh t.

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15/23

a cht mi trng Nhm 2

-Tn tht v kinh t c nh gi c hai i tng l nh nc v t nhn.Tntht chung l gim din tch t.-Th d nh t nm 1983 n 1990 th trn Tn Chu mt 45.000m2 t,160 cnnh.Ti sn tht hi c tnh khong 16 t ng.

ng H Ch Minh on A t - A Tp (t km387 + 400 n km420) cn 31 im st l taluy nghim trng, c ni ln n hng chc ngn mt khi t (nh). Cng ty c phn Qun l ng b Tha Thin - Hu phi huy nghng chc u xe khc phc s c, tm thi cho thng xe, nhng mt s im tikm393 v km402 n chiu 24-10 vn cn b vi su trong t gn 10m, gy khkhn trong vic gii ta tip theo. Cng theo cng ty ny, gii ta hon ton cn tnht thm 10 ngy trong iu kin thi tit bnh thng. c tnh thit hi do st lt gy ra khong trn 10 t ng

Caracas Venezuela l ni thng xuyn xy ra cc v l t gy thithi rt ln v ti sn.Ch trong nm 1993 c tnh thit hi do l t gy rakhong 7.1triu la.VI.Cc cng tc d bo v phng chngtrt t.1.D bo trt l.

1.1 Cng tc quan trc.Cng tc quan trc l mt trong nhng bin php quan trng theo di,d

bo v nh gi mc dch chuyn.Cc phng php quan trc thng c sdng bao gm:

-Phng php vin thm.-Quan trc hin trng.

a/Phng php vin thm.H thng cc t liu vin thm cho php nh gi tc dch chuyn,xcnh cc yu t a mo thun li cho s dch chuyn .

Cc ti liu vin thm c th s dng hiu qu trong quan trc l nh v tinhSPOT,ERS,ASTER v nh my bay .

Ngoi ra ngy nay phng php vin thm c s h tr v kt hp vicng c GIS gip phn vng d bo s uc nhiu thun li hn qun l v gimst tai bin trt l.

b/Quan trc hin trng.-S dng cc phng tin thit b hin i o c,nh gi nhng bin

ng nh trong t vi cc thng s x l v hin th trc tip qua my tnh.-Ni dung:theo di s bin dng ca ca mt ttheo di s pht trin ca cc

vt nt,s dch chuyn ca cc ct mc quan trc,tc mt t.1.2 Lp bn d bo.-Bn phn vng d bo tai bin l t l c s chn la cc v tr quan

trc c hiu qu v phng php quan trc thch hp.

- 15 -


16/23

a cht mi trng Nhm 2

-Ni dung chnh ca bn l khoanh nh nhng vng c mc ri ro vtrt t theo mc ,theo ngun gc v theo c ch khc nhau.

-Bn phn vng d bo phi trn nhng thng tin c bn kt hp vi ccthng tin trong lch s. l nhng thng tin quan trng d bo tai bin trt lt ngt.

2.Phng chng tai bin l t.-Qun l quy hoch s dng hp lti nguyn t ai l bin php hu hiu

gim thiu tai bin v tn tht do l t.-Bin php phng chng tai bin l t thng c trin khai theo hai

hng sau:+Lm tng lc khng trt.+Lm gim lc trt.

2.1.Cc bin php lm tng lc trt.-Tho kh nc sn: mc tiu l thot nhanh nc mt v nc di t

tng nng,chng li vic tch nc sn.-Tng cng n nh ca b vch bng lp ph thc vt,bng lp ph

,bng bm ht xi mng.-To chn chn khi trt2.2.Cc bin php lm gim lc trt.-D b ti trng trn b vch.-Lm gim gc nghing ca mi dc v gim chnh lch a hnh.-Lm gim s ph hy chn i b vch.

3.Mt s bin php khc.* phng chng trt t c hiu qu, ngoi nhng gii php v khoa hccng ngh nu trn, cn phi kt hp vi cc gii php khc nh:

- Tuyn truyn su rng trong nhn dn v nguyn nhn v hu qu ca cctai bin thin nhin ni chung v trt t ni ring.

- Thnh lp cc Ban phng chng tai bin thin nhin cp x v cc nhmtnh nguyn vin cp thn bn i ph vi tai bin c hiu qu.

-Phng php thit k thi cng, khc phc s c trt l, duy tu, bo dngng.

-Bin php gia c v phng h b mt sn dc, mi dc.Cc bin php phng chng v thot nc mtCc bin php phng chng tc dng ph hoi ca nc ngm.Bin php gim ti trng pha trn khi trt.-Cc bin php xy dng cng trnh chng .-Cc bin php ci to tnh cht ca t .-Bin php phn vng d bo nguy c trt

- 16 -


17/23

a cht mi trng Nhm 2

VII.Khc phc hu qu do trt t gy ra.-Sau khi trt t xy ra, cch tt nht lm cho n dng li l tc ng vo

qu trnh m khi trt bt u. Trong nhiu trng hp, nguyn nhn ca trt tl tng p sut nc v trong nhng trng hp nh th th nh hng ca qu trnhlm kh phi c t ln hang u.

-N bao gm nhng rnh thot nc trn b mt ti im bt u trt t b sung nc mt t s thm nhim v nhng ng tho nc ngm hoc gings tho nc v lm gim p sut nc. S tho nc lm tng s chng li sc mnhca vt liu trt v v vy lm n nh mt trt.

-Sau khi ma bo khng khip xy ra ngi ta ghi nhn c s chuyn ngca mt trt 300 b nhn chm xung lp bin i hnh th. Khi trt su xpx 40m, lan rng 150m v di 300m. Trt t th gn cc nh my thy in v vyhnh ng ngay lp tc tng chng nh l cn thit.

. -iu tra khoa hc cho rng nu mc nc h xung khong 5m s tng

cng s chng chu tng cng s n inh ca dc trt. S lm kh c thchin bi vic o hm, mng, lm cc thanh ngang, khoan cc l tng kh nngchng chu ca nn khu vc . Sau khi lm kh, s dch chuyn s kt thcvo ma ma ti, thm ch lng ma c tng cng khng quan st thy mt hintng dch chuyn no xy ra.

B.Cc hin tng lin quan ca trt t.I.Sp ln.

1.Sp ln l g?Sp ln l s di chuyn theo chiu thng nglm mt t b h thp t t

cho n t ngt ca mt vng vi din tch vi din tch thay i rt nh(chng vi

m2) hoc rt rng ln (hng ngn km2)2.Nguyn nhn gy sp ln.-Qa trnh a cht ngun gc ni sinh(hot ng t gy).-Qa trnh a cht ngun gc ngoi sinh(tc dng ph hy ca mch nc

ngm).-Do con ngi to ra trong qu trnh con ngi tc ng vo t nhin(khai

o,khai thc ti nguyn).3.Cc nhn t nh hng ti sp ln.-Tng tc gia hot ng ca con ngi v iu kin a cht l nhn t nh

hng to ln n sp ln, vi tc ln xung v n nh vt cht Tri t rtchm

-S vn ng ca cc vt liu bn trong lng t cng nh hng mnh mti s sp ln.

4.Phn loi sp ln.

- 17 -


18/23

a cht mi trng Nhm 2

-Phn ln cc chuyn ng sp ln l sn phm ca qu trnh ngoi sinh vnhn sinh.

-Theo phng thc th hin c th chia sp ln lm ba nhm sau:+S do mt i vt liu pha di.

+Sp ln do s tho kh cht lng.+Ln do s gia tng ti trng trn b mt.4.1 Sp do mt i vt liu pha bn di.

Phn vt liu b mt c th l a cht d ha tan.Ni c phn vt liu b mts to thnh h sp.

Sp ln c gy ra bi cht lng rt khi ngun nc ngm hoc s sp tng nc mt v t gn mt t qua nhng khong trng di t.

S thu du c kt hp kh v nc tng nc ngm, hn hp hi v nc

ca nng lng a nhit gy ra sp ln4.3 Ln do s gia tng ti trng trn b mt.y l kiu thng gp trn nhng vng t c nn kt cu yu nhng li b

tr cc cng trnh xy dngln.5.C ch sp ln.C ch sp ln thc s lin quan n s kt ni ca cc ht ring l vi nhau

hnh thnh mt khi bi p sut thp ca cht lng. S sp ln ca cc khu vc cdu ni chung lin quan n s gim to ln ca p sut cht lng cho n 2,8.107Pa, su ln (hng ngn m) v din tch nh hn 150m2.

Mt khc, hu qu sp ln t vic thu hi nc ngm c quan h vi s gimmnh p sut cht lng, thng nh hn 1,4.106 Pa, ti su t hn 600m c linh tng i vi khu vc rng ln khong hng trm km2

C ch ca chuyn ng khi thng ng thay i theo cc kiu dch chuynkhc nhau.

5.1 Sp,st ln do mt vt liu rn.-Khi mt b phn trong nn t b mt i pha trn khong trng va c

hnh thnh lc cng nn p xut hin ko phn bn trn vo ch rng to lps cn bng mi,kt qu lm cho mt t b h thp xung.

-V nguyn l dch chuyn ny s dng li khilc cng ny t ti gii hn

cn bng.Ngc li,lc cng ny to khe nt ct trong phn vm ca mi l hng.Quy m vng b nh hng ph thuc vo quy m vng b mt i v khong

cch t trn l hng cho n mt t.5.2 Sp ln do tho kh.-Khi lu cht trong b khai thc m khng b sung kp thi,lc cng b

mt gia cc ht gim,di p lc ca khi nn pha trn,s dn t vt liu s xut

- 18 -


19/23

a cht mi trng Nhm 2

hin lm gim th tch cc l rng.Kt qu lm gim b dy ca trm tch,gy nnhin tng h thp mt t-hin tng ln.

-Do s dn ttrong khng c tnh n hi nn nhng vng b ln hngth phuc hi.Bin ln khng ch ph thuc vo l rng ca t m cn phthuc vo b dy ca tng t b tho kh.

-S dch chuyn trong c ch ny din ra chm chp,kh nhn bit trctp,nhn bit qua cc du hiu gin tip thng qua cc s liu quan trc.

5.3 Ln do bin i thnh phn vt liu ca nn v ti trng bn trong.-Khi b thm nc nhiu cc vt liu d b ha tan v b mang i lm cho

khi nn chuyn v trng thi khng n nh.Khi ti trng bn trn ln hn sc chung ca nn,hin tng ln xy ra.

6.Tai bin sp ln.Cng nh tai bin trt l hng nm gy thit mng hng trm nghn ngi

khp ni trn th gii bn cnh cn c cc vn v kinh t xy ra.

- Vit Nam vn sp l hai bb b cc dng sng vn ang din ra gythit hi v kinh t6 v ngi.

-VD:Sp ln xy ra gn b sng Cai Cn lm sp nhiu nh ca ngidn.c tnh thit hi khong 350 triu ng.

S sp ln H Peigneur, Louisiana- Abizare l th d ca s sp ln lin quan n m mui vo ngy 21 thng

10 nm 1980 pha nam Louisiana, khi h cn vi chiu su trung bnh 1m, crt ht mui trong l st bn di. St xy ra sau khi mt mi khoan du y xung

l trong mt m mui cn ang hot ng, v tr ca n di su 430m so vib mt v mui ca o Jefferson. Khi l m rng ra do nc ct mui c lmsch v ha tan, mui nay nm trn mt ca l st, m l st l sn phm ca s stln l ln.

-H rt qu nhanh khin 10 s lan, mt tu ko v mt l khoan dubin mt trong vng xoy dng nc vo bn trong m, ni c ng hm rng nh4 xa l v cao 25m.( S khai m c thc hin vi s tr gip ca xe ti v xe it.) Thng thng c 50 th m v 7 ngi trong 1 l khoan du. S sp ln gy tn tht hn 25ha o Jefferson, bao gm khu vn sinh hc lch s, ta nhxanh, v 500.000$ nh. Bn tri ca khu vn th b ph v bi khe nt ln, l s

dch chuyn mnh m ca t n b h. Nhng t gy do lc cng v thng xyra ra h st ln.7.D bo v phng chng tai bin sp ln.7.1 D bo tai bin sp ln.-Lp bn phn vng d bo tai bin sp ln y l phng tin hu hiu

d bo v phng chng tai bin sp ln.Bn phn vng cng thch hp chotng loi nghin cu nh:

- 19 -


20/23

a cht mi trng Nhm 2

+Bn a cht cng trnh.+Bn ia cht thy vn.+Bn s dng t.+Bn phn b cc cng trnh khai thc khong sn.

+Cc p nc cc ging khoan di nc v du kh.-Kho st theo di vngang nm trong nguy ctai bin sp ln.Ni dung:

+Thng k cc tai bin xy ra.+T chc quan trc s h thp mt t.+D bo mc tn tht c th xy ra.

-D bo cc tai bin t bin.7.2 Phng chng tai bin sp ln.-Qun l vic khai thc nc di mt t,du m v kh t trn t lin.-Quy hoch v gim st cht ch vc khai thc khong sn.

-Xy dng quy phm gim sat cng tc tho kh khi thi cng cc cng trnhngm.

-Qun l quy hoch,thit k nh ca theo c im ca nn t.-Tuyn truyn cho mi ngi dn thy c tc hi ca vic sp l t.II.Tuyt l.-Ltuyt l hin tng thin nhin gy nguy him cho nhiu ngi.-Do s chn ng no xy ra trn ni tuyt cng lm cho tuyt c s dch

chuyn trn cc sn dc.-Bng l phn cng hn ca tuyt.Phn ln nc trn tri t chng ta tn ti

di dng bng tuyt.Cn tuyt bng l di chuyn rt l nhanh chng. Nu nh c nhiu , t v

cy ci kt hp vi nhau th n cng ging nh mt khi bng l. Ging nh trtt, s trt l tuyt vt cht cng c mang i v chng li lc trt l.

*Phn loi l tuyt.-Trt l tuyt c th xy ra tuyt t v tuyt kh v c 2 loi: trt l

dng v trt l khi-Trt l dng: xut hin khi tuyt c kt dnh km, c xu hng

kt thnh nhng khi nh v thit hi m n gy ra khng ln.

-Trt l khi: lc u mt khi trt c th thay itwf 100-10.000m2 v b dy 0,1-10m

-Nhng khi trt l ln rt l nguy him, gii phng ra mt lng nnglng v cng ln bi vic huy ng hang triu tn bng v tuyt xung vi tclc 5-30 m/s (tng ng 18-100km/h) hoc hn th na. S dch chuyn trn mtngang hay s va chm tahy di gi tr t 5-50 tn/m2 nhng trng hp ln hn,

- 20 -


21/23

a cht mi trng Nhm 2

nguy him hn c th ln n 100 tn/m2. Tm quan trng ca s tn cng mnhny cho thy ch cn 3 tn/m2 cng gy sp c nhng cu trc btng vng chc.

-S trt l c bt u khi mt khi lng bng tuyt ln trn cao trtxung do s qu ti ca lng tuyt mi hoc s thay i bn trong mt khi tuyt khu vc c sc chng chu km km theo s ph hy. Thm ch nhng iu kin

kh bt n, trng lng ca mt ngi trt tuyt cng c th gy ra trt l. Khimi bt u, s trt l c khuynh hng i theo cc ng trt, cu trt, vttrt. y l xu hng ch yu, tuy nhin trn vng st l cng xut hin nhngng mn khng gii hn. Nhng li st l thng c mt vi nhnh , rnh gnnh hp li v trt xung. V vy vi v trt l tuyt di chuyn ngang qua cc lichnh trong mt khong thi gian ngn c th ri t trn nh xung di. y lmt thiu st khi khng nhn ra kh nng ny lm mt i sinh mng ca nhngcng nhn ang don dp rc t v trt l tuyt u tin b vi lp trong ch mtgiy.

Nhng mi e da ca l tuyt.

-Nhng ngi trt tuyt cc ni cao hay cc vch ni l nhng ngi b eda u tin khi hin tng trt l xy ra, tip n l cc khu du lch min ni, bitth, ng tu, ng quc l v cc khu vc khc ca mt vi thnh ph.

-Mt v d ng ch Juneau-th Alaska xy ra mt v trt l tuytht sc nghim trng. Khong 100 nm trc, mt dc lao nguy him trn Juniangy ra bng v tuyt 6 ln v n tin ra ti bin.Khng c thit hi nghim rng not vic trt l tuyt xy ra hn th k qua nn c cc cng trnh c xy dngngay qua ng trt. Nu c mt v trt l ln khc xy ra n s ph hy khong30 nh ca, mt phn trng hc, khch sn bn ng v kt qu l r ln nhngting m m gh s t cc bn tu-ni m hng trm tu thuyn ang neo u.

Ngi ta c tnh rng, khu vc trt l xy ra, nhng gia nh sng 40 nmc 96% b nh hng nhng hu ht h tr nn th vi mi nguy him ny.III.Ngoi ra cn c mt s tai bin khc.

1.Nt t(cc hot ng t gy).-Nt t cng l mt hin tng tai bin ca mi trng.Hng nm gy tn

tht ln cho nhn loi.-Nguyn nhn ca nt t:

+Vic khai thc qu mc ngun nc ngm.+Cc chn ng nh trong lng t.

-t gy hot ng l mt dng tai bin a cht rt nguy him bi t thn n l mt dng tai bin ia cht, ngoi ra n c th gy ra cc dng tai bin a chtkhc nh: ng t, trt t, nt t nh hng ti tc vng bn ca cc cngtrnh xy dng, ph hu hoc lm h hi cc cng trnh h tng c s quan trng.t gy hot ng l cc t gy bt u hot ng t 10.000 nm v cho n ngyhm nay vn hot ng v chng u l cc t gy sinh chn.

- 21 -


22/23

a cht mi trng Nhm 2

2.L Bn.-S hnh thnh cc loi hnh l qut khc nhau nh l qut sn, l qut

nghn dng v l qut hn hp ph thuc vo iu kin thi tit v mt m (ahnh, thm thc vt, v phong ha - th nhng). cc trng v cnh ng karst lnthng xy ra l qut nghn dng, cc trng nh hn (thng l cc bn lng) c th

xy ra l qut hn hp, l qut sn v l bn . Nhng ni c sn dc xy ra lqut sn v l bn . cc thm sng ln c th xy ra l ng, mt dng ca lqut hn hp.

-L bn l mt hin tng l lt mang theo cc lp t .-L bn gy nhng thit hi to ln cho con ngi.VD: Cc trn l t v bn l do cn bo Durian gy ra. Bo Durian b

vo Philippines. Bn v t l nhn chm nhiu lng mc pha ng nam th Manila.Con s ngi thit mng chnh thc c thng bo l 406. Hin vn cn398 ngi b mt tch.

u thng 10/1969, thi tit kh hanh ko di, m thp (Thi Nguyn) t 30-35%. Ngy 16-19/10/1969 nh hng ca rnh thp pha ty km khng kh lnh yu didng ng t, gi nam, ng nam thi v lm m tng 60-65%. Chiu 20/10 lc cc ma ro nh. Khong na m tri ma to v rt to xy ra trong thi gian khong 1h45, thi gian nh ca l bn khong 15-20. Theo iu tra th mc nc dng cao ca ral 3,6-4 m, lu lng d tnh 200-250 m3/s, vn tc t 5-7 m/s.

Thit hi chnh bao gm 22 gian nh b tri cng ton b t trang ca hc sinh vgio vin, 26 hc sinh c in cht, 20 mu la v 10 mu hoa mu b mt trng.

C.Li ch ca trt t.

-Ngoi nhng thit hi do trt t gy ra trt t cn c nhng tc ngcho cc nh khoa hc v cc nh a cht nghin cu v trt t,v cu to ca vtri t...

-Trng i hc M-a cht nghin cu khoa hc v cc vn trt l,acht,trc a... Ni dung nghin cu cn tin hnh l tm hiu su v hin trng ccdng tai bin a cht, phn loi, xc nh cc nguyn nhn xy ra tai bin; c chhnh thnh, d bo nguy c cc tai bin; phn vng d bo v xut cc gii phpquy hoch, phng trnh, bo v mi trng

-Cc nh khoa hc trn th gii nghin cu v trt t nhm tm nhng tliu v s hnh thnh tri t.

Phn kt lun.-Trt t l mt dng tai bin thin nhin xy ra tng i ph bin cc

vng i ni.-Hu qu gy ra do cc v trt t rt ln gy tn tht v ngi v ca

nhiu nc trn th gii.- Qu trnh trt t chu tc ng ca cc yu t t nhin nh: a cht, a

mo, kh hu, thy vn, thm thc vt..., ng thi va chu s tc ng ca con

- 22 -


23/23

a cht mi trng Nhm 2

ngi nh: ct xn chn dc, tng ti trng trn sn dc, n mn, hot ng ca ccphng tin c gii...

- Hu qu ca trt t l rt nghim trng nn cn kt hp cc gii phpkhoa hc cng ngh v gii php kinh t - x hi mt cch ng b vic phngchng trt t c hiu qu cao.

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