Tsp chi Khoa hoc DHQGHN, Khoa hpc Ty rhien va Cong nghe. Tap 29, So 4 (2013) 8-15
Ap dung phuong phap Rada ddt dS xac dinh “thoat khdng”
dual be tong ban mat dap Ctta Dat
D6 Anh Chung\ Nguyen Van L g i\ Vu Due Minh^'*
' Vien Sinh that va Bao ve cong tritth - Vien Khoa hoc Thuy Leri Viet Nam
~Tru&ng Dai hoc Khoa hoc Tu nhien, DHQGHN, 334 Ngiryin Trai, Ha Not, Viet Nam Nhan ngay 20lhdng9nam 2013
Chinh sua ngay 25 thSng 10 nara 2013; chip nhan dang ngay 20 thang 12 nSm 2013
Tom tit: Trong c3c cong tnnh thuy loi n6i chung, cac dap da do, be tong ban m |t noi rieng, sau khi hd a'ch nude giua Idp be tong ban m |t v& dap da do thudng xuit hien hiSn tuemg “thoSi khong”. Day la hifn cuong tach ede Idp vat lieu khac nhau gtita tam be l6ng ban mat, Idp Vila 16t va Idp dem tao ra khoang rang c6 the chiia nude hoac khong khi Khi g |p hien tutyng nay v i^
phin bd UDg suit va co chi lam viec ciia cac tim be tdng ban mat sd bi anh hudng \h tac d$ng den kha ndng chdng thim va tudi tho cong trinh Bai bao gidi thidu mdt so ket qua mdi thu du(?c khi ting dvng phuong phap Ra da dit de xac djnh nhanh hien tuong “thoat khong” dudi tarn be tdng ban mat tai dSp hd chila nude Ctia Dat - huydn Thudng Xuan - tinh Thanh Hda.
Tie khda: ddp dS dd, bd tdng ban mat, “thoat khdng"
1.E t van de
Hi?n nay, dap da do c6 bS tong mat (Concrete Face Rockfill Dam - CFRD) la ket cau dap dang duoc ung dung pho bidn tren the gidi. Day la loai dap c6 tinh an loan cao, khong kdn chon dieu kien dia hinh dia chat, c6 the thi edng b moi dieu kien thoi tiet, tan dung dugc toi da ede logi dd thai loai dao tir ho mdng trim ho|c dirdng ham thao lu, mang lai hieu qua 1cm ve kinh te va ky thuat [1].
Trong thbi gian qua, a Viet Nam da xay dimg mot so cong trinh thuy Igi c6 ling dung
cong nghe nay nhu dap be tong dam Ian Son La, dap da dd cd bd tdng ban mat Cua Dat, Thanh Hda...
Trong thuc te, khi cac dgp n&y dugc dua v&o sii dung, nhat Ik ede dgp c6 chieu cao 1cm thudng cd su bieo dang ciia thSn dap nhu lun, chuyen vi... Mat khac, bd tdng blui mat m |c db dugc thiet ke c6 chieu day mdng, nhung lai Ibm bang be tdng cot thep • day la loai vat lieu ciing nen khdng the udn theo sir bien d^ng cua m |t thugng linj, ciia than d§p, d in den hien tugng mat tiep xuc giua be tdng ban mat va phan edn lai cua than dap. Ket qua la tao ra khoang trdng giua Idp dudi be tdng ban mat va phan con lai cua tbSn dap, ma theo cac nha nghidn cuu ciia Trung Qude goi hien tugng nay la hifn tugng
D A Oiun^ va nnk. /Tap chi Khoa Iwc DHQGHN, Khoa hoc Ttr nhien va Cong nghf, 29, S5"4 (2013) 8-15
“thoat kh6ng” [1, 2]. Chinh vi ly do ban mat mat tiep xuc vdi tbSn dap nen duoi tdc dung ciia trgng lire ban thSn Idp bg t6ng vk nhit la ap lire niroc 1km cho lop be t6ng ban mat d l bj nut ne d in den ro ri, tham lau nude qua thin dap.
Vi vay, vi?c xae dmh vj tn “tholt khong” dS xii la yeu cau dat ra d6i vdi clc cong trtnh dap eo cau true bS t6ng ban ma^. D i xac dinh chinh xac vi tri “thoat khdng" duoi nhung tim bS tong, chiing t6i da nghiSn ciiu su dung phuong phlp R a da d it b ln g thigt bi SIR System - 30 6 dap Cua Dat, Thuong Xuan, Thanh Hoa.
2. Phinmg phap nghien cihi 2.1. Nguyen ly cua phutmg phdp Ra da dat
Phuong p h lp Ra d a dat (Ground Penetrating Radar - GPR) la mot phuong phlp Dja Vat ly boat dong d^a tren nguyen ly cua su Ian truyen s6ng dien tu uong moi trudng d it dl.
Khi ang ten phat ra s6ng diSn tu tin so cao tu 10^ -r 10® MHz, song nay duoc Ian tray€n xuong mdi trudng dat dl. Khi song d i ^ tu gip c ic ranh gidi vat chat c6 hlng so d i|n mdi khic nhau no se bj tan xa, khde xa hole phan xa.
Sdng phan xa quay trd lai gap mat dat v l dugc Ingten thu ghi lai. Tm hieu cua sdng phan xa se phan Inh nhOng thong tin ciia mdi trudng dia ch it phfa dudi.
Do sau tham than cua phuong p h ^ phu thude vao tan so cua in g ten phit thu va tmh chit vat ly ciia mdi trudng dja chat trong do gil trj hang so didn mdi tuong ddi va do din d i|n (o) la chu yeu. Tan sd cang cao, dd din didn va hang sd dien mdi cing Idn tW chieu sau khao s ^ cing nho.
T u nhOng ranh gidi giua cIc tarn be tong vdi lop lot ludn ludn ton tai mat phan xa sdng didn tu, vdi h§ sd phan xa dupe tmh theo edng thux; sau:
D -
trong dd: - II hang sd didn mdi tuong ddi ciia mdi trudng thu nhat; h ln g sd dien mdi tuong ddi cua mdi trudng thii hai.
Nhu vay ranh gjdi giua cic mdi trudng vat chat cang cd su khac bidt vd g il tri hang sd £ e n mdi thl Ip dung phuong phlp Rada d it clng cd hieu qua. Bang 1.1 la bang tong hop hlng sd dien mdi cua m§t sd vat chat thuong g |p trong tu nhiSn.
Bang 1. Hang so di|n mdi cua mdt si tu nhien
it chit trong
Su T6n vlt chat Gil trj hlng sd Ghi didn mdi e, chu
1 Khong khi' 1
2 Dit khd 5
3 Dat udt 25
4 Nude ngpt 81
5 Datbdi 5-30
6 Dit set 5-40
7 Da phiin sic 5-15
8 Da granic 4-6
9 Dl vdi 4-8
10 Cat khd 3-5
11 CItudt 20-30
12 Nude bien 80
2.2. Thief bi s u dung
De thuc hien nhiem vu da dat ra, chiing tdi sir dung he thiet bi SIR-30 do Cdng ty GSSI ciia My san xuat [3]. Thiet bi bao gom m§t tram m iy chii (Hinh 1) v l he thing angten cd tan sd tu 15MHz den 900MHz. Viec lira chqn cac angten dua vao hai yeu to: Dp sau nghien ciiu va dd phin giai ciia Ingten.
D A. Chung vg nnk. /Tap chi Khoa hoc DHQGHN, Khoa hoc Tu nhien va Cong ngh^ TSp 29, So 4 (2013) 8-15
Hinh 1. thiet bj Ra da ddt SIR-30.
Do sSu cua phuoTig p h ^ phu thuoc vk> tan so cua angten va giS tri hang so dien m6i cua moi
tnrcmg d it dd. Voi cung mot moi tnrong khao sat §ngten c6 tin so c ^ g tbap thl chieu s§u nghiSn cuu cang Ion nbung do phSn g i^ c ^ g thap, c6n d6i voi angten tan so cSng cao thl nguoc lai.
2.3. NghiSn a m thirnghi^m tren mo hinh Dpa trSn c a so tong quan c^c k it qua nghiSn cixu trgn th i gioi, ket hop voi dieu k i|n thuc te ciia c ic d |p 6 Vi?t Nam c6 vat lieu l^t mai tren dap la bS tong, chilng tdi da chon va x ly durng mo hinh nghi&n cun thit nghiem trSn lop dat doi (dac tnnig cho vat lieu dat d ^ dap) vS c6 he s6 mai 1:3, cdc hang xdi ngam nSm duoi c^c lop bS tdng v l lop Idt da duoc lap day bang cdc vat li|u thd nhu c it v ^ g , soi.. Lop be tong c6t thdp v i be tong khong cot thep c6 chiiu d^y la 20cm (hinh 2).
Hjnh 2. M6 hinh thi§t kl hang xoi ngim nSm dudi Jdp be t6ng va dd Idt rr K it qua thii nghiem tren mo hinh nSu tten
cho thay, phuong phap Ra da dSt da xdc dinh duQfc hang xoi ngim diroi lop bS t6ng c6t thep
va bS tdng kh6ng c6t thep voi angten 900MHz (hinh 3).
D.A. Oiung va nnk, /Tap cbi Khoa Itpc DHQCHN, Kluja hoc Ttr nliien va Cniig ng/jc. Tip 29, So 4 (2013)8-15
Mnh 3. Ket qu4 xSc djnh mo hinh hang x6i ngim nim duoi b6 t6ng ISt m&i bing Sng ten c6 sd 900MHz.
VI vay, vdi hieu qua ciia phuong phdp Ra d a d^t trong viec n ic dinh c ic hang x6i ngSm dudi lop bS t6ng, chdng t6i da quyel dinh 5p dung phuong phap n4y de nghien cmi hien tugng “thoat kh6ng” b dap Cira Dat, Thubng Xuan, Thanh Hda.
3. K it qua nghien cun
3.1. Khu v\fc nghien ci q u m sat
i vd hg thong tuyen
H6 chiia nude Ciia huydn Thuong Xuin, tinh Thanh Hda 1^ cong trinh thuy Im ket hop vdi thuy dien ddng vai tro quan trong I&
chua, dieu phoi nude ndng nghiep v& sinh ho^t eho nhan dan trong viing vdi tong dung tjch chua nude \k 1,45 ty dung rfch huu ich Ik 0,79 ty (U nh 4).
Hinh 4. Vi tn dap be tdng ban mdt Cua Dat.
D3p ho chua nude Cii'a Dat c6 chieu dai la 930m, cao tiinh dinh dap la -i-121m. Dap chan nude Ik d |p trong luc dk do, phan phia mai thuong luu duoc t?o bdi Idp ban mat bang be tdng cot thep c6 chieu dky Ik 0,7m (phia dudi chSn) vk thu dkn ISn d in cao trinh +116m Ik 0,3m (dinh dap). Ldp bd tong ban mat duoc chia lam 78 tam vdi chieu rpng moi tam bS tong la 12m. C6ng trinh duoc thi cong xong vk dua vko su dung tu thkng 7/2009 (Hinh 5).
D A Chung va nnk. /Tap chi Khoa hoc DHQGHN, K]ioa hoc Tie nhieii va Cong nghe. Tap 29, So'4 (2013) 8-15
Hien tgi, trong q u i trinh d |p vfn hkih va svc dung, duai tac dyng ciia tSm be tong cot thep va dp lire nircrc nen tren dap m6t so tam be tong ban mat 6 phia thugng Imi da xuat hien hien tugng ran nut, cong venh d in den hien tugng 1dm mat tiep xuc gi&a cac tlm be t6ng vdi than
dap. Vi v |y vi^c xdc djnh "thodt kh6ng” nam ducri ede tim be tong cot thep Id can thiet, de serm CO phuxmg dn xu ly kip thoi vd hifu qua.
nhdm ndng cao chat lupng edng trinh trong miia mua lu.
Hinh 5. Hi|n trang dap be tong ban mat Ciia Dat Thanh Hda.
De giai quyet nhiem vu dja chdt nham phat hien “thoat kh6ng” trong cac tdm b6 t6ng ban mdt tai d |p Cira Dat, chimg toi b6 tri hS thdng tuyen do theo myng lirdi 5 vu6ng, khoang each gi&a cac tuyen do Id Im va chiSu d ^ tuySn do
12m (bang chieu rpng cua tam be tong). Truong hgp phat hien nhOng khu virc c6 nghi ngo
“thoat khdng” thi eSn phai dugc tien hanh do chi tiet hon (Hinh 6)
Hinh 6 H? thdng tuyln quan sat bdng phuong phap Ra da ddt.
D.A Oiung va nnk. /Tap chi Khoa hoc DHQCHN, K3ioa hoc Tir nhiirt va Cong iighe, 29, S6'4 (2013) 8-15
3.2. MpT SO k it qua cMnh
Trong pham vi kiem tra “thoit kh6ng” duoi tim be tong ban mat ciia 40 t5m be t6ng dap chi'nh ho chiia nu6c O ia Dat tinh tir m i^ nuoc thvc te (a tai then diem kiim tra) cao trinh
+83.3Im 16n den cao trinh +110.0m; sau qua trinh do d ^ thirc le va xii 1}?, phSn rich s6 lieu [4], chdng toi da xac dmh dugc nhieu vi trf bfi t6ng ban mat c6 hifn tugng “thoSt khong”. Sau dSy la mgt so ket qua dien hlnh dirge bieu dien tren ede hinh 7, 8, 9.
Hinh 7. Ket qua kiem tra tren tim 64, tuySn do thu 3.
Hlnh 8. Kit qua kiSm tra tren tim 64, tuyin do thu 14.
D.A Chung vii mik. ITqp chi Khoa hoc DHQGHN, Khoa hoc Tu nhiin va Cong ngh^ l&p 29, So 4 (2013) 8-15
Hinh 9. Ket qua kiem tra tren tSm 69, tuyen do Uni 5.
Kec qua khao sit tren cho thay tai vi tn bi
"thoit khong” tW m it phan xa tii lop thep va phan tiep giip giSa be tong ban mat va lop dat d i bj bien d?ng, uon cong mot each rat ro ret (Hinh 7 v i 8). Tren hinh 9 cho thiy c6 hiSn tir<?ng “thoit khong” nhimg lop thdp ben trong van khong bj bien dang hay thay doi. Tuy
nhien, theo ket qua khao sit ciia phuong phip Ra da dat chung toi chira xac djnh dirpc chieu d iy ciia lop “thoit khdng”.
Hinh 10 biiu diln vi tri cic “thoit khdng”
dirpc xic dinh bang phirong phip Ra da d it t?i dap Cita Dat.
T69.G
Hinh 10. Vi tri “thoatkh6ng” dupe xac dinh bang phuong p h ip Radadit,
D.A Qtung va nnk. ITgp chi Klioa hoc DHQGHN, Khoa hoc Tir nhien va Cong nghe. Tap 29, So 4 (2013) 8-15
4. Ket Iu |n
T u ket qua do thu nghiem trSn mo hinh v i k€t qua xSc djnh “thoat kh6ng” tren b6 t6ng mat cua dap Cira D^t, chung toi c6 mot so nhan xet sau:
+ Phuong phdp Ra da dat sir dung thiet bi SIR System 30 ket hop vdi cac 3ng ten c6 tin so 400MHz, 900MHz c6 the xac djnh dirot v|
tri cac “thodt khSng” nam dudi cdc tarn bS t6ng ban mat.
+ Vdi phuong phap o^y cd the xdc dinh dugc vi tn cua cac Idp thep irong cic tim be t6ng bOT m5t, cung nhu xac dinh dugc mat ddy cua cdc tim be t6ng. T u do c6 thS xic dinh dugc cac tarn bS tong cd hien tugng bien dang hay khong.
+ Tuy nhiSn, vdi cac nghiSn cuu ban diu nfeu tren, chua xdc dinh dugc chiSu d iy cdc Idp
“thodt khdng”, Chung toi se tiep tyc nghien cuu hoki thien viec ap dung phuong phdp Ra da dat v io muc di'ch nay nhSm nSng cao hiSu qua cua phuong phdp va cong bd ket qua trong cac so tiep theo.
Tai li|u tham khao
[1] Annan A.P, Sensors & Software Inc., Ground Penetrating Radar Workshop Notes, 1992 [2J Cal Jun and al. Application of Ground
Penetrating Radar to Investigation of Near- Surface Fault Properties, Seismology Society of America, 1996.
[3] SIR-System 30, Manual, Geophysical Survey Systems. Inc; 2013,
[4] Radan for Windows, Manual, Geophysical Survey Systems, Inc; 2013.
Applying the Method of Ground Penetrating Radar to Identify
“Air Escape” under the Concrete Slab Layer at Cua Dat Dam
Dd Anh Chung’, Nguyen Van Lffi’, Vu Due Minh^
'/nstiru/ejor Ecology and Works Protection, Vietnam Academy for Water Resources
’ VNU University o f Science, 334 Nguyen Trai, Thanh Xudn, Hanoi, Vietnam
A bstract: In irrigation works in general, concrete face rockfill and concrete slab layer dams in particular, after accumulation lake then between the concrete slab layer and the layer of riprap dam often appears "air escape". This is the phenomenon of splitting the different layers of materials between the face rockfill, mortar lining and cushioning to create voids that may contain air or water.
When encountering this phenomenon, the disuibution o f the elongation and the working mechanism of the concrete slab layer will be affected and influence the ability to work, the ability to waterproof and the longevity of the work. The paper introduces some new results obtained by applying the method of Ground Penetrating Radar to rapidly identify the phenomenon o f “air escape” under the concrete slab layer at Cua Dat reservoir dam - Thuong XuSn distnet - Thanh Hda province.
Keywords: face rockfill dam, concrete slab layer, "air escape".