32(1), 172-180 Tap chi CAC KHOA HOC VE TRAI DAT 6-2010
M O T S O K E T Q U A Q U A N T R A C B I E N DONG THAM TRONG CAU TRUC DE BANG CONG NGHE
DIA DIEN DA CUC VA PHAN CUC KICH THICH
TRAN C A N H , D O A N V A N TUYEN,
PHAN THI KIM V A N , A. WELLER, M. MOELLER
I. MO DAU
Ngdy nay, dudi anh hudng cua qua trinh bie'n ddi khf h t a toan cdu, cac hien tugng thidu tai nhu dug lyt, vd de, tragi Id ddt, lu quet, lu bun da,... do nudc lu sdng len cao vd mua - bao ldn xdy ra ngdy cang ttag. Mdt ttong nhung tham hga nghiem trgng do lu, bao gay ra la sy cd vd dd sdng hoae de biln. Nguyen nhan ddn de'n vd dd chfnh la bie'n ddng thdm qua than, nIn de. Qua trinh thdm lau gay ra xdi mdn ngdm, mang vat lieu khdi dd trong thdi gian lu cao va dai ngay. O cdc nudc cd hd thdng dd dieu phdng chdng lu lyt va phyc vy phdt triln kinh td' - xa hdi, sy cd vd dd gay ra cdc tdn thdt ldn v l ngudi vd co sd vat chdt. D l chu dgng phdng chdng thien tai lu lyt ddi vdi de sdng, hudng nghien cdu phat triln cdc he thdng quan ttde dd (HTQTD - dike monitoring system) dang dugc chu trgng phat triln d cdc nude ed he thdng dd phdng chdng lu, lut. He thdng nay cho phep thu dugc nhung thdng tin v l cac bid'n ddng ttong cdu true dia chdt, tham so thdy ddng lyc va cac tham sd dia ky thuat cua cdng tnnh dd dudi tdc ddng cda nudc lu va cua cac ydu td khac nhdm thutag xuydn ddnh gia chat lugng dd va canh bdo cac bie'n ddng bdt lgi ddi vdi dd [1,3, 11].
He thdng dd dilu (HTDD) mien Bdc Viet Nam cd tdng chieu dai tren 5.000 km. Cac tayen dd ndm hai ben cac sdng ldn nhu sdng Hdng, Chay, Ld, Thai Binh va Ma. Cdc tuye'n de ndm ttai tren cac vung cd dilu kidn dia chat - kie'n tao khac nhau, dieu kidn dia mao phflc tap, da dang. Mat khac, HTDD cdn ehiu tab hudng manh me cua dieu kien khi hau nhiet ddi ndng dm, mua nhita. Bdi vay cac tuydn de tten HTDD thudng tidm an nhieu loai dn hga ed thi gay su cd mat dn dinh eho de. Dae biet
la thudng xuydn tdn tai cac vi tri de xung ydu ttgng diem, ma htag nam c t a phai theo ddi, duy tu bao duong va chudn bi cac phuang tidn, vat lieu va nhto lyc dy phdng khi mua lu de'n.
Va'n de quan ttde dich chuyin nen de bang thiet hi Inclinometer va quan trdc thay ddi dp lyc nudc dudi nen de bdng thie't bi Piezometer da dugc trien khai d Viet Nam rii 1995 ddn 1996 [5]. Cac sd lieu quan ttde da cung cdp thdng tin ve hidn trang nen de tai vung xung quanh vi tn dat thie't hi do. Tuy nhidn vdn d l thie't lap HTQTD bao gdm td hgp cdc thidt bi dia vat ly - dia ky thuat de theo ddi sy bie'n ddng lidn tyc cdc tham sd dia ky thuat, dia vat ly cua nIn de va mdi tradng ven de, phuc vy canh bdo tai bie'n de ttong mua lu lyt d nudc ta, chi mdi dugc thd nghiem trong vai nam gan day.
Bai bao nay gidi thieu he thdng quan ttde ve bien dgng thdm ttong cau true dd bdng cdng nghe dia didn da cue va phta cyc kfch thfch (multi-electtods electrical resistivity and induced polarization) vd mdt sd ke't qua ban ddu thu nhan dugc td HTQTD thd nghiem tten doan dd ttgng diem ta ngan sdng Hdng, tai Vtt Thu, tinh Thai Binh.
II. BO TRI HE THONG DIEN GUC VA THIET BI DO
He thdng dien cyc dugc bd tn ttdn mdt tuyd'n ngang qua dd, d trang tam vung dd yd'u trgng dilm.
Tren tuyd'n nay da thidt ke va lap dat mdt hd didn cyc btag thep khdng ri dang thanh dai 25 cm dudng kfnh 10 mm ; sd eye la 50, khoang each cue la 1 m. Hd cyc dugc dat d do sau 0,5 m each mat dd va CO dd. Hinh 1 la so dd bd tn he didn cyc cua tuyen nay. Tuye'n do quan ttde thugc doan dd ta ngan sdng Hdng td 169 H- 000 m de'n 169 + 250 m, tai Ngd Xa, xa Nguydn Xa, huyen Vu Thu, tinh
Thdi Binh. Day la mdt ttong cac doan dd yd'u ttgng diem cdp tinh. Theo tai Ueu cua co quan quta ly dd tinh Thai Binh, doan de nay cd cdu true dia chdt nen ddt yd'u. Trong thdi gian mua lu cac nam 1996, 2002 da xdy ra sy cd nguy hiem : chta de phia sdng hi xdi. Id ; ea dd phfa ddng bi dun chdy, nudc dun sdi vung chan de phfa ddng manh ; sdng cao
nudc uan qua mat de. D l nang cao do an todn, nam 2004-2005 doan dd da dugc gia cd bang lat ke da, ddp md ban d chan dd phfa sdng. Vung ddm chan de phia ddng dugc la'p ddt cat pha, ca dd phia ddng va mat de dugc md rdng ; vung chan de phfa ddng dugc xd'p cac khdi da phan ap vdi chieu ddi 100 m va chieu rdng 3-4 m.
6 4 2 0 -2- -4- -6- -8- -10-
Phfa dong IViatde
. Q -
Phia song Hong
10 20 30
X(m)
40 50 60
<r- Hinh 7. So dd bd tri he dien cue do giam sat de 1. Cac dien cue dugc dat
d do sau 0,5 m, 2. Mat de va co de, 3. Muc nude sdng, 4. Tram do (T)
Hinh 2a la quang canh cua doan de nghien cdu.
Cdng tac do dac thu nhta so lidu dinh ky dugc thye hidn trong tram quan ttde (T). Thidt hi do su dung la mdy do dia didn IP - Geolight 4 Points Hp cdng sua't l o w , CO sd Lippman chd' tao tai Ddc. Dac dilm ky thuat cua thie't bi dugc md ta ttong [6].
Qua trinh do (hinh 2b) dugc dieu khien ty ddng bang phdn mem Geotest [8]. Uu dilm cua phto mem Geotest la : cdc gid tri do dugc hien ngay tren man hinh notebook ; ngudi do cd thi kilm tra mang so lidu do, ndu dilm nao cd sai sd ldn thi do lai duoc.
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Hinh 2. Vi tri tuye'n quan ttde (a) vd thie't bi do tai thuc dia (b) T - Tram do, CS - Tuye'n do ngang dd
III. M O T S O KET QUA DO GIAM SAT
1. Kit qud quan trdc Men dgng de ndm 2008 vd 2009
Ve CO sd tota-ly va b t a chdt cua qua trinh phta cyc kfch thich cung nhu nguydn ly che tao may vd
phuang thfle do da cd trong cdc cdng trinh [7, 9]. 0 day cac tdc gia chi trinh bdy cac ke't qua quan trdc bid'n ddng thdm trong cdu true dd bdng cdng nghe dia didn IP.
Cdng tae quan trdc dugc triln khai dinh ky theo thang, tuta va ngay. Trong mdt so ngay cd lu cao
thudng do Idy sd lieu khoang 2 gid/ldn. Khdi lugng sd lieu thu dugc ttong khotag thdi gian tfl 28 - 02 - 2008 den 17 - 10 - 2009 la rdt ldn.
Tai lieu dugc phan tich bang phdn mIm AC2DSIRT do eac ddng nghiep Ddc da cai tie'n phta mIm DC2DSIRT [4]. Dilm mdi cua phdn mdm ndy la ttong qua trinh phan tich cd dua vao hieu chinh do cao [2] cua cac didn eye dat d do sau 0,5 m cdch mat da't.
Nhu da bidt, phta bd cua cdc mat cat ldp dien ttd sudt (DTS) phta anh cdu true eac ldp ddt cua mdi tradng phfa dudi dgc theo tuye'n quan sdt.
Nguge lai, nhtag bid'n ddng ttong ca'u true dia chat cua mdi tratag se duge phan anh trong phta bd cua eac iiiat cdt ldp DTS do dugc. Mdc do bie'n ddi tutag ddi (BDTD) theo thdi gian (Delta(t)) cua DTS, tfnh ra phta tram dugc xac dinh theo cdng thfle :
Delta(ti) = [DTS(ti) - DTS(t0)]^TS(t0)*100 vdi DTS (ti) la mtag sd hdu do d cac thdi dilm sau ; DTS (tO) Id mtag sd lidu do tai thdi dilm trade Idy lam chudn.
Hinh 3 la eac mat cat ldp DTS do trong hai ngay 29 - 7 va 30 - 7 cua mua Ifl nam 2008. Trong hai ngay nay nude sdng Hdng d mdc cao 2,90 m va 3,30 m trdn muc nudc bao ddng cdp I (2,18 m). Tfl hinh 3 nhta tha'y rdng bid'n dgng DTS cua mat cdt ngang de ttong thdi gian khoang 30 gid cd gid tri la td -5 dta H-6,5 %. Dang luu ly Id mdc do BDTD cua DTS mang gid tri am cd dien tich ldn hem dien tfch mang gia tri duong va cd xu hudng md rdng td phia sdng vao phfa ddng. Dilu nay ed mdi lidn he vdi mflc do thtai nude cua ddt thta va nen dd dudi tac ddng lien tyc cda thuy lye ddng sdng, bdi vi, eung mdt loai ddt, khi cd do thdm nudc cao thi DTS giam.
10 20 30 Ohrn'm
0 6 8.4 12 17 24.134.2 48.5 68.8 97.7138.5
S.'^T^J .JJ^^'-:
Delta=^%_+6,5%
... '
Delta= -6% _ +4%
• %
Delta= -5% _ +4"/^
-12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12
Hinh 3. Bie'n ddng DTS ddt dd ttong ngay 29 va 30 - 7 - 08 a) Cdc mat cat ldp DTS, b) Cac mat cdt bie'n ddng DTS ttrang ddi Bie'n ddng ttong cac mat cat ldp DTS do trong
cac thdng 3, 6 - 8 nam 2008 dugc dta ra tren hinh 4. Mdc do bie'n ddng DTS dat dd thay ddi kha rd net, gia tti BDTD (so vdi mang sd lieu do vao 28 -02 - 2008) tii -40 % dd'n -H15 %. Cac thang 6 - 8 diu la thang cd myc nudc sdng cao, do dd mdc do
bie'n ddng ed cao ban cac thang khac. Trdn mdi
mat cdt BDTD nhta thdy hai vung cd gia tri khac
nhau : vung cd gia tri tfl -40 % dd'n -i-2,5 % va vung
cd gia tri td 4-2,5 % de'n -1-15 %, ranh gidi la dudng
dang -1-2,5 %. Phto dien tich vdi gia tri bid'n ddng td
-40 % dd'n -1-2,5 % nam d eac ldp dat d mai dd phfa
sdng ldn han so vdi phto gia tri bid'n ddng td hutag tfl phfa sdng vao phfa ddng cua cac ldp thta H-2,5 % dd'n -H15 % d mai dd phfa ddng. Dilu nay dd khi myc nudc sdng len cao, bdi le DTS giam phta anh dinh tfnh mdc dd tham nudc tang theo xudng khi cac ldp ddt than dd bi ngdm nudc.
20 30 BTS (Ohm-m:
0 6 8.4 12 17 24.1 34.2 48.5 68.8 97.7 138.5
mmmm
100 -80 -65 -50 -35 -20 -5 5 20 35 50 65
Hinh 4. Bid'n ddng DTS ddt de trong cac thang 3, 6 - 8 nam 2008 a) Cac mat cdt ldp DTS ; b) Cac mat cat bid'n ddng DTS tucmg ddi
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^ -5:
-10 J
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'«-'i; R=o 85 110709, lOh
R=0_80 120709.4h
0:
-5:
10-
10 20
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30
Delta=
40 50
-20% _+2,5% :
DTS (Ohm'm)
0 6 8.4 12 17 24.134.2 48.5 68.8 97.7138.5
30 Delta (%)
-100-80 -65 -50 -35 -20 -5 5 20 35 50 65 80 100
<- Hinh 5. Bid'n ddng DTS da't de trong cac ngay
11 v a i 2/7/2009 a) Cac mat cat ldp DTS, b) Cac mat cdt bie'n ddng
DTSUitagddi
Mflc do BDTD cua DTS cde ldp ddt dd ttong cat ldp DTS (a) da nhto dugc mdi quan he cua mdc cac ngay 11 va 12 - 07 - 09 ed gia tti td -20 % de'n do bie'n ddi DTS ddt thta vd nen de vdi qud trinh H-5 % (hinh 5). Khi phta tfch dinh lugng cac mat nudc dp lyc tii phia sdng vao phfa ddng trong thdi
gian cd lu. Tai cac thdi dilm luc 7, 11 va 18 gid ngay 11 - 07 - 09 myc nudc sdng Hdng tuong tag do dugc la 2,90, 2,59 va 3,07 m, trdn myc nudc bdo dgng cdp I (2,18 m). Tai vi tri tuye'n do X = 13,2 m da xac dinh dugc cao dd ranh gidi tten cua ldp ddt cd DTS = 17 ilm tuong tag vdi 3 mat cat DTS la : 2,06 m, -1,98 m va -1,30 m (hinh 5).
Nhu vay vi tti cua dutag dang dm dugc ntag ldn phfa mat dat mdt khoang 0,74 m. Dieu nay cd nghia la ttong khotag 20 gid nudc sdng da tham theo phuong thang dtag dugc 0,74 m. Phta tfch hai mat cdt mdc do BDTD (b) d 2 thdi dilm do ldc 10 gid va 12 gid etag thdy sy khde bidt nhilu ve mdc do chfla nudc ttong thta vd nen dd. Rd rtag la vdi myc nfldc Ifl cao khotag 3,0 m thi ttong khotag thdi gian tii 10 gid, 1 1 - 0 7 - 0 9 de'n 6 gid, 12 - 07 - 09 ddt thta va nen dd da ttd ndn bao hda nudc.
Hinh 6 la phta bd DTS (a) va BDTD (b) quan trdc ttong cdc thang 3, 6 - 8 nam 2009. Mflc dd
bie'n ddng DTS da't dd thay ddi kha ldn, gia tii DTD tii -65 % de'n -i-15 %. Dac bidt, ngay 25 - 06 - 09 cd mdc do BDTD am manh, gia tri td -65 % dd'n -10 %. Mdc do BDTD cd gia tri am phan anh tat ca cac ldp da't dd tiJr ttdn be mat xudng dudi nIn dd diu bao hoa nudc.
Trdn co sd Idy dutag dang tti 17 Qm lam chudn, da thfl xac dinh dao ddng ranh gidi cua ldp ddt tuang tag vdi ldp ed DTS = 1 4 - 1 7 fim va mdi lidn he vdi dao ddng myc nudc sdng ttong cac thdng 3, 6 - 8/2009. Tai vi tti x = 32 m tten myd'n do, da xac dinh dugc cao do (H - so vdi myc biln) cua dutag dang tri 17 Qm, tuang tag vdi cac thang tten la -1,24, -1-0,36, -1,31 va -2,49 m. Myc nudc sdng ttong cac ngay do tuong tag la 1,25, 2,00, 2,67 va 1,59 m.
Chdnh lech cao do cua dutag dang Ohm ttong thang 6 va thang 8 la : 0,36 H- 2,49 = 2,85 m. Dieu nay cd nghia mflc do thadi cua vat Ueu dd giam di manh d eudi mua lu.
<^ Hinh 6. Bie'n ddng DTS ddt dd cac thdng 3, 5, 7 vd 8
nam 2009 a - Cdc mat cdt ldp DTS, b - Cdc mat cat bie'n ddng
DTSUitagddi
0 6 8.4 12 17 24.134.2 48.5 68.8 97.7138.5 -100-80 -65 -SO -35 -20 -5 5 20 35 50 65 80 100
Td eac kit qua quan ttde, da xac dinh dugc xu the bie'n ddng DTS theo do sau va thdi gian cua cac ldp da't de, ggi la cdc dutag cong dd sau (sounding curves) - hinh 7 va bdng 1.
Budc ddu cd the nhta dinh ve dac dilm bie'n ddng DTS cua cac ldp da't de nhu sau :
1. Mdc do bid'n ddng DTS theo thdi gian cua
cae ldp dat dd nam tten muc nudc biln manh ban cae ldp ddt de ndm dudi muc nudc biln. Trong thdi gian cd lu bie'n ddng manh ban ttong mua khd.
2. Ve gia tti DTS, cac ldp dat nam ttdn cao do
0,17 m d thta dd phfa ddng va ttdn cao dd 0,55 m d
thta dd phfa sdng cd khotag bie'n ddng Ita, ttrang
tag tfl 15 de'n 50 Qm va tfl 13 dd'n 28 Qm.
Bdngl. Cao do titong ufng vdi cac dudng cong bien ddng DTS
Sd dudng Caodd
Vi tri xdc dinh tai mep de phia dong
3,17 2,17 1,17 0,17 -1,32 -2,32 -3,32 -4.32 -5,32
Sd dutag
Caodd 4,55 3,55 2,55
Vi tri xdc dinh tai mep de phia song
® ® ® (7) ®
1,55 0,55 -0,45 -0,95 -1,45 -1,95 -2,45
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6/1/08 12/18/08 7/6/09 Date
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1 12
6/1/08 12/18/08 7/6/09 Date
<- Hinh 7. Bita ddng DTS ddt de theo do sau va thdi gian
a, b - LSig vdi cac diem dd sau d mep de phfa ddng ; c, d - tJhg vdi cac dilm dd sau d mep de phfa sdng
11/14/07 6/1/08 12/18/08 7/6/09 1/22/10 Date
12/18/08 7/6/09 Date
3. BQiotog bie'n ddi DTS cua cac ldp ddt ndn dd, nam dudi cao do 0,0 m cd gid tri thdp va gdn nhu nhau d nen de thudc ca hai phia sdng va ddng, gia tii tii 3 - 4 de'n 17 - 20 Qm.
V t a d l mdi kha ly thu la bdn canh cac ket qua vi mat cdt ldp DTS, cdn nhan dugc cae mat cdt tham sd ^ (^ - dac trung eho tinh chdt phto cyc cua mdi tratag [7, 9] ; nguyen ly do dai lugng nay ttong [6]). Chung phta anh dac dilm thach hgc va dac dilm didn hda eua mdi tratag de. Hinh 8 la eac mat cat ldp DTS (a) va tttcmg tag la mat cat ldp tham sd cp (b) nhta dugc ttong cdc thdng 10, 11 va 12 - 2008.
Phta tich cac mat cat tham sd q) cd thi nhta thdy ^ac_di|m cda mdi.„tradng ddt dd iihu sau :
a) Cdc ldp ddt dd cd dac diem dien hod kha phdc tap, kha ntag nap didn (chargeability) kha cao, vdi gid tti tfl 1,5 dd'n 18 mrad (mill radian) ; b) Trong mat cdt ngang dd, theo hutag td phfa ddng ra sdng, dac dilm dita hda dugc phta thanh 3 vung : vung ca dd phfa ddng (PD), vung trang tam de (TT) va vung phfa sdng (PS) ; hai vung PD va PS cd gid tri
^ tfl 1 de'n 6 mrad, vung TT cd gia tri ^ td 6 dd'n 18 mrad. Tuy nhien, ranh gidi - dutag dang gia tri 6 mrad, cua cac vung lai ludn bidn ddng do qua trinh tdc ddng cua ddng thuy lyc sdng ; c) Ke't hgp eac sd lieu phto tfch cac mdu ddt de bang va so lieu do IP cd the xdc dinh mdi tucmg quan chat che gitta tham sd phta eye cp vdi cdc loai dat khac nhau ttong cdu true dd.
2. Bien dgng mtfc nudc song Hong vd muc nudc ngdm vdng chdn de phia dong
Tae ddng thuy ddng lyc cua nude sdng ttong thdi gian ed lu Id ye'u td quan ttgng gay ra qua tnnh tha'm trong cac ldp da't thta, nen de va lam bie'n dang manh eac ldp da't hai ben co dd. Do nguy hilm ddi vdi dd ttag khi myc nudc lu ttag vd cutag dd cac ddng thdm tfl phia sdng vdo ddng tang. BQii ddng thdm chdy manh se ldi keo vat lidu de vdi khdi lugng Ita dd xdy ra xdi mdn ngdm chan de vd gay vd de. Bdi vay vide quan ttde bita ddng cua myc nudc sdng va myc nude ngam phfa ttong de cung dugc thye hien cung vdi quan trdc cac tham sd dia vat ly - dia ky thuat. Hinh 9 phta anh bie'n dgng myc nudc lu sdng Hdng va myc nudc ngam vung phfa chta dd phfa ddng. Dac dilm cua mua lu hai nam 2008 va 2009 : cd 4 Ito dinh lu (a) vugt qua mdc bao ddng cap II (3,12 m), bdng 2, thdi gian myc nudc sdng vugt qua mdc bao ddng
cdp I (2,18 m) dai hta. Mdt dac dilm ntta la ca hai ngudn nudc sdng va nudc trong ddng deu ed anh hutag cua muc dao ddng thdy trilu htog ngdy.
3. Bdn ludn ve do an todn cua doan de theo sd lieu quan trdc 2008 vd 2009
Nhu da md ta d muc I, doan de thd nghidm la doan dd xung yd'u cdp tinh vd da dugc gia cd nam 2004 - 2005. Vay cac kd't qua quan trdc bid'n ddng nam 2008 va 2009 cd thi cho phep bta luto vd do an tota cua doan dd nhu the' ndo ? Cac sd lieu trdn bdng 3 la ca sd cho mdt so danh gid vl do an toan cua doan dd. Trade bet, cdn luu y, hai mua lu nam 2008 va 2009, myc nudc lu sdng Hdng len cao hta myc nudc bao ddng ca'p II (3,12 m) tai vung de nghien eta chi trong ft ngay. Myc nudc Ifl sdng Hdng chu yd'u d myc bao dgng cap I. Hai mua lii khdng xay ra mflc nudc bdo ddng cdp IH (4,12 m) - hinh 9 va btag 2.
-^ Hinh 8. Mat cdt DTS va mat cdt
tham so ip a) Mat cat DTS,
b) Mat cdt ip
12 20.2 34.2 57.8 97.7 165 1 2.5 4 5.5 7 9 10.5 12 13.5 15 16.5
Bang 2. Ke't qua theo doi muc nudc lu (m) hai nam 2008 - 2009
Ngay/thang
06/ 7 - 02/8 08/8 - 18/8 01/11-15/11
06/7 - 23/7 01/8 - 06/8
Cue dai Cue tieu Ndm 2008 3,50 3,98 4,02 Ndm 2009 3,40 2,78
2,03 2,19 2,10
2,19 1,84
Trung binh
2,69 3,09 2,92
2,72 2,25
Phta tfch cae sd Ueu quan ttac d bdng 3 nhto tha'y : a) Bie'n ddng DTS lidn quan chat che vdi bid'n
ddng tham ttong cdu true de va thuy lyc nudc sdng
khi cd lu. Tuy nhidn, quan he dinh lugng thi cdn cd
nghien cta bd sung ; b) Trong thdi gian lu sdng
Hdng d mflc bao ddng tfl cdp I trd ldn thi eac bilu
hidn thdm nudc td phfa sdng vao phfa ddng la ttog
len. Cy thi ttong cac ngay 07-7 va 10-8 mua lu
2008, cac ngay 11-7 va 16-7 mua lu 2009 myc
nudc ngdm phfa ttong ddng (thdng vdi nudc sdng)
ldn cao ban be mat radng dang ttdng mdu tii
-1-0,05 m dd'n 0,45 m. Dita nay cd nghia la nd'u nhu
vung chan dd phfa ddng chua Wp ddm bang ldp cat
pha hoae chi la radng cdy Ida thi hidn ttrgng dun
sdi manh d vung chta dd phfa ddng da xdy ra, vd
neu thdi gian lu bao ddng cdp II keo dai mot sd
Uito thi se cd sy ed mdt dn dinh d doan dd nay Tuy
nhien, tren thuc td' thi ehi thi hien nudc chay ri d vung chta de phfa ddng. Nhu vay, theo phan tfch dinh tinh tfl cac kd't qua quan ttde, cd thi nhan dinh rang, doan dd thu nghidm hien tai cd do an tota cao khi ma myc nudc lu sdng Hdng d mflc dudi bdo ddng cdp III (4,12 m).
Vdn de xay dyng cac chi tidu, giai bdi toan md hinh vdi cae tham sd thu nhan dugc tfl he thdng quan trae nhdm danh gia chdt lugng dd theo thdi gian va canh bao sy cd de trong thdi gian cd Ifl Ita tren sdng Hdng la y tutag thuc hita tie'p theo cua cdng ttinh nay.
AGR 111= 4,12m
<— Hinh 9. Bie'n ddng myc nudc tai vi tri quan trdc
a) Myc nudc sdng Hdng,
b) Myc nudc ngam phfa trong ddng AGR I - myc nudc bao ddng cap I, AGR II - myc nudc bdo ddng cdp II, AGR III - myc nudc bao ddng cdp IE
12/18/08 Ngay. thang
Bang 3. Bien dong cac tham so dia vat Iy va thiiy van doan de thut nghiem 2008 - 2009 Ng., th..
nam (1) 26-3-2008 01-6-2008 07-7-2008 10-8-2008 26-3-2009 11-7-2009 16-7-2009
Bie'n ddng DTS dat de (%)
(2) -25--1-15 -35--1-15 -40 - -1-15 -40 - -1-15 -35--1-15 -20 - -1-2,5 -60--1-10
Muc nudc song Hong (m)
(3) 1,10 1,15 2,97 3,70 1,25 3,07 2,60
Myc nu6c ngSm phfa dong (m)
(4) 1,30 1,37 1,45 1,85 1,20 1,55 1,50
Hieu sd cot (4) v a H = 1,40m*
(5) -0,10 -0,03 +0,05 +0,45 -0,20 +0,15 +0,10
Bieu hien quan sat dugc Uen mat de
(6) 2 phfa c0 de khd 2 phfa C0 de kho Nudc thfai b CO de phfa dong
2 phia ca de, chan de phia ddng ri nu6c
Mat de khd
Chan va co de phia dong ri nudc
Chan va co de phia dong rinudc
* Gia sd nudc ngdm vung chta de phfa ddng va cao do so vdi myc biln cua vung radng d chta dd phfa ddng, noi dat hd khoan do bid'n ddng myc nudc ngam.
KET LUAN
1. Vide lya chgn phuang phap cdng nghd dia didn da cyc va phta cyc kfch thfch do bang quan ttde bid'n ddng tham ttong cdu true de la phu hgp va cd hieu qua.
2. LSig dyng hai cdng nghe nay dl theo doi bid'n ddng thdm ttong cdu true dd ttdn eac dgan dd yeu ttgng dilm da cung cdp nhung thdng tin ve dae
trung phta ldp, bie'n dang thdm vd dae dilm didn hda cua mdi tratag de theo thdi gian va khdng gian. Cac thdng tin ndy se gdp phta ddnh gid chdt lugng de va canh bao cdc bien ddng bdt lgi ddi vdi doan dd trgng dilm, dac biet la cac bie'n dgng cd thd gay sy cd sat Id mdi de, ddng chdy ngam manh ttong cau true dd va vung bi xdi ngdm dto de'n vd de trong mua lu.
3. Kd't qua budc ddu theo ddi bien ddng trong
cdu true dd (km 169 +000 + +250, de ta ngan sdng
Hdng tai Vu Thu) trong hai mua lu 2008 - 2009 nhu sau :
- Bie'n dgng tuong ddi DTS theo ngay mdi tmtag ngang de Uong thdi gian lii cao uen mflc bao ddng cap I va nhd hon mflc bao ddng cap EH, dat gia tri tfl -20 % de'n 6 %.
- Bie'n dgng theo thang dat gia tri tfl -65 % de'n 15 %. Vdi gia tri bie'n ddng nay, khi muc lii d mflc bao ddng cap n, cac ldp dat dd d trang thai bao hoa nudc va bieu hien tham, ri nude d ca de va chta de phia ddng, lam ye'u de.
- Mflc do bie'n dgng DTS cua cac ldp dai dd trong mila khd la thap hem mflc do bie'n ddng trong mua lii. -
Ldi cam on : kei qua nghien cflu thudc nhiem vu HTQT ve KHCN theo Nghi dinh thu Viet Dflc, 2005-2009. Bd Khoa hgc va Cdng nghe Viet Nam (MOST) va Bd Dao tao - Nghidn cdu khoa hgc CHLB DUe (BMBF) da tai ttg. Cac tac gia chta thanh cam on C0 quan chu quan, chu tri, cac co quan quan ly de dieu Trung uong va tinh Thai Binh.
TAIUEUDAN
[1] T. DAHLIN, P. SJOEDAHL & S. JOHANSSON, 2008 : Embankment Dam Seepage Evaluation from Resistivity Monitoring Data. Near Surface 2008 - 14th European Meeting of Env. and Eng. Geophysics Krakow, Poland, 15 - i 7 September 2008.
[2] TH. HENNIG, A. WELLER, TRAN CANH, 2005 : The effect of dike geometry on different resistivity configiuation. Joumal of Applied Geophysics, 57, 278 - 292.
[3] S. JOHANSSON, 2004 : Detection of intemal erosion in embankment dams - Possible methods in theory and practices. EBL, Oslo.
[4] A. KAMPKE, 1999 : Focused imaging of elelectrial resistivity data in archaeological prospecting. Joumal of applied geophysics, 41, 215 - 227.
[5] TA VAN KHA, TRAN CANH, 1996 : Uiig dung td hgp cac phuang phap hien dai nghien cflu dd dn dinh cua de va anh hutag cua eac cdng ttinh xay dung ven de. Dia chat - Tai nguyen, Nxb.
KH&KT, Ha Ndi, 287 - 296.
[6] E. LIPPMANN, 2008 : Manual_4PointIight_10W.
Erich Lippmann Geophysikalysche Messgeraete, Germany.
[7] PREM V. SCHARMA, 1997 : Environmental and Engineering Geophysics. Cambridge University press, 252 - 264. Web : http//www.cambridge.org.
[8] A. RAUEN, 2008 : Geotest user Manual.
Geophysik- Dr. Rauen, Wallefing, Germany.
[9] J. M. REYNOLDS, 1998 : An Introduction to applied and Envuonmental geophyics.John Wiley
& Sons ; 522 - 552. Web : http//vvww.wiley.eom.
[10] J. SCHOEN, 1983 : Petrophysik. Akademie Veriag, Berlin, 276 - 286.
[11] P. SJOEDAHL, T. DAHLIN, B. ZHOU, S. JOJIANSSON, 2002 : Monitoring of leakage in embankment dams through resistivity measurement- a 2,5D Modelling study. Procs.Bth Meeting of EAGE, Aveiro, 8-12 /9/2002.
S U M M A R Y
Monitoring results on permeable changes of dike structure by geoeiectricai multi-electrods induced
polarisation technology
This paper presents a part of dike monitoring system to observe dike stmcture by geo-electrical multi-electrodes technology and induced polarization, which has been installed at significant weak points of the Red River's dike in Thai Binh province.
The primary results show : a) The monitoring system with the electrodes array installed at dike body is operating smoothly ; b) The daily changes on resistivity structure of dike's soil layers at the flooding time were small, from -20 to +5 % ; Monthly changes determined from -65 to +15 % in comparison those in the dry time ; c) Based on the observed resistivity images the permeable changes from the river through the dike body at flooding time have been determined.
Ngdy nhdn bdi: 22-12- 2009 Vien Dia chdt (Vien KH & CNVN)
Vien Dia Vat ly - CHLB Ddc