KHOA HOC CONG NGHE
PHAIXI TtCH IVldT s d IVHAIM TO AIXJH HUOIVIi DEIV OI\l D!I\IH D A P B E TOIXJG
Nguyen Quang Himg' TOMTAT
Noi dung trinh bay trong bai bao nay tap trung di sau nghien cmi vao phuong phap can bang cue han va ling dung ddi vdi van d6 dn dinb dap be tong trong luc xay dung tren nen da va khong phai da Thong qua do, khao sat mot so nhan td nhu chieu cao dap. chi6u rong dap, luc dinh ciia nen, gdc ma sat trong ciia nen, chieu sau chon mong.., anh hirdiig toi dn dmh dap be tong xay dung tren n^n. Cac k6t qua nghien ciru cho hinh anh ro net ve su thay doi he sd on dinh dap theo cac Uiong so co ban nhu kich Uiuoc dap, di^u ki^n dia chat, di€u kien thi cong dap. Cac ket qua nghien ciiu la co so cho cac nghien cmi tiep theo nham hoan thien tieu chuan thi^t ke dap be tong.
Tit khda.: Bap be tong trong lire, can bSng cue ban, he sd on dinh.
1 . BAT VAN BE
Theo thdng ke ciia Hdi dap cao the gioi ICOLD, Viet Nam ed khoang 10.000 dap Ion nho cac loai (phan bd a 41/61 tinh thanh nhung tap trung chii yeu 6 mien Bdc va mien Trung) trong dd cd khoang 460 dap Ion diing hang thu 16 trong sd cae nude ed nhieu dap cao trdn the gicn. Tuy nhien su phan bd ve hinh loai dap theo loai vat heu khdng ddu nhau theo chieu cao. Neu nhu voi ehidu cao dap nho hon 100 m thi dap vat lieu dia phuong chiem tdi hon 80% (Hinh 1), tuy nhien ddi vdi chidu cao dap Idn hon 100 m thi dap be tdng ndi chung vd dap be tdng trpng luc ndi rieng lai chi^m mpt ty le dang ke (hinh 2). Hon nira.
trong nhung nam gan day, vdi tinh hinh thieu hut ve san Itrgng dien, Viet Nam da tien hdnh xay dung hang loat cdng trinh thuy dien vdi chieu cao dap tuong ddi Ion da phdn deu sii dung hinh thiic dap be tdng trpng luc nhu Dinh Binh - Binh Dinh (42 m), Se San 3 - Gia Lai (60 m), A Vuong - Quang Tri (80 m).
Son La - Son La (130 m). Long Sdng - Ninh Thuan...
Phan loai theo th^ I09I dap
ILL
Q S p v a l l i e i i D3pb>Hinh 1. Phan loai dap theo loai hinh vat U^u (H<100m)
Phan loai dap theo chf^u cao tren IOO111
ULLIL
Oap OTTL Dap be long v i mT h e l o i i
Hinh 2. Phan loai d ^ theo loai hinh vat lieu (H>
100 m)
Dap be tdng trpng luc thudng dupe xay dung tren nen da va cd nhiing dang Uen ket khde nhau tuy thude vao miic dp xu ly nen cung nhu di^u kien dia chat nen. Dang thii nhat la dap be tdng trpng luc duoc xay dung true tiep tren nen da du cudng dp, miic dp xir ly nen viia phai, ddi vdi loai nay cd the coi nhu dap duoc dat true tiep tren nen. Dang thii 2 la dap be tdng trong lue dupe xay dung tren nen da da xu ly, thdng thudng chieu sau xii ly nen Idn nen truong hop nay thdng thudng dap dupe chon sau vao
Hinh 3. Dap be tdng xAy dung true ti^p tren n^n
' Tmdng Dai hoc Thiiy Sai
KHOA HOC C O N G NGHE
dupe dinh nghia la mdt mat lien tuc xuat phdt tii phan nen thupng luu dap vd ket thiic tai nen ha luu dap. So dd tinh cua phuong phap dupe the hien tren hinh 5.
Hinh 4. Dap b& tdng xSy di^ng sdu vao n6n Bdi vdi dap be tong xay dung true tiep tien nen:
Dap duoe dat true tiep tren ndn, trong tinh toan kiem tra on dmh thudng dup'c kiem tra tai mat tiep xiic giiia dap va nen. Dieu kien kiem tra on dinh truot eua dap duoc tien hanh dua tren viec so sdnh cac nhan td chdng truot va cac nhan td gay trupt tai mat tiep giap giiJa dap va nen (Hinh 3).
Ddi vdi dap be tong xay dung sau vao nen: Dap dugc chon sau vdo nen, trong tinh todn ki^m tra 6n dmh cd hai quan diem khac nhau. Quan diem thii nhat Id coi tac dung eiia hai khdi nen thuong luu va ha luu nhu cae tai trpng ngoai vd viee tinh todn kiem tra dn dinh duoc tien hdnh tuong tu nhu dang thii nhat. Quan diem thii hai la sir dung phuong phap can bang thoi de xet tinh dn dinh eiia dap va nen. Vdi quan diem nay xem nhu khdi nen thupng, ha luu dap vd dap cd eimg mdt mice do du trii on dinh nhu nhau (Hinh 4).
Neu nhu trong phuong phdp phan thoi, bd qua nhiing anh huong tuong tdc giiia cdc thdi thi ve ling xii tai trpng trong quan di^m thii hai cd the xem gdn nhu la trong quan diem thii nhat. Do vay, lua chpn phuong phdp phan thdi de nghien ciiu cac nhan td dnh hudng d^n dn dinh tong thi ciia dap be tong trpng lue se mang tinh tdng quat vd thuc te hon.
2.KErQUAniGHBIGIhl
2.1. Phdn tich dn dinh trugt ddp be tdng theo phuong phdp phdn thoi
2.1.1. Cac gii thiet cua phuong phap - Tinh theo can bang cue han.
- Cae he tmc tpa dp XOY va TON dup'c dat tai phia trai cua thoi va tuan theo " Quy iroc ban tay phii' (Chi^u duong cua gdc a nguoe chi^u kim ddng hd).
- Tieu chuan phd hoai dupe sii dung theo Mohr- Coulomb.
2.1.2. Phuongphip tinh
Ndi dung cita phuong phdp dupe xde dinh dua trdn eo sd" can bang eua toan he thdng dap va nSn lam viee tuong tdc ddng thoi voi nhau. Mat trupt
.^ V
Hinh 5. So dd tinh tjodn
Phuong trinh can bang diing de xac dinh dd du trii 6n dinh cua cac thoi.
, p>_ 1(H^ +t^Xtan0^,cosa, 4-sintt,)-t/, lanf>,,(^j. -^K\
j:{tan^j, sintr,-cosO;}+ '^A (cosff,-tanizjy, sina;) Trong dd:
i - sd thii tu mat truot dang phan tich.
(P,.i - Pi) • tdng cae luc tdc dung phuong ngang len khdi da thii i.
Wi" tdng trong luong nuoc, dat, dd, hay he tdng eua khdi thii i.
Vi - Tdng cae lue tac dung phia tren khoi ndm thiri.
Tan ij) di = tan flii / FS
FS: Dd du trii on dinh cua phan tich (he sd an todn).
(|)i - gdc ma sat trong cua khdi ndm thii i.
u, - gdc hpp giira mat truot thii i va phuong ngang.
Ui - luc thiiy tinh day nguoe tdc dung Idn mat trupt thii i.
HLJ - cac luc tac dung theo phuong ngang d' tren hoac dudi tac dung ben phia trai khdi trupt.
C<„ = C,/FS.
C, - Luc dinh don vi tinh tai mat trupt thii i.
L, - chieu dai mat trupt thii i.
2.1.3. Chuang tiinh tinh toin
He sd an toan on dinh theo phuong phap phan thdi dup'c xde dinh dua trdn nguyen ly can bang gidi han thong qua chuong trinh tinh ODDBTrL-TU2009
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 2 - THANG 5/2019 49
KHOA HOC CONG NGHl
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tiTiat sau cua dap be long tiong luc theo hai hetiiohi tieu chuan Nga-Viet va Mf nam 2009 ciia Tnrong Dai hoc Thiiy loi [6].
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Hmh 6. So d6 khdi chuong trinh ODDBTrLTU2009 phdn tich 6n dinh dip TBTL
' 2,63 -h 5,23, he sd an todn Fs thay doi cang nhieu phu thupc vao gdc ma sat trong is? eua ndn. cf) cang Idn thi Fs cang thay doi nhidu. Tuy nhidn khi chi^u cao dap thay ddi Ion dan thi miic dp anh huong nay se giam di. Khi chieu cao ddp cao den 30 v 40 m thi yen cdu ve cudng dd nen da tang Idn ro ret. Dap chi dam bao an toan dn dinh khi nen dat cudng dp 4) > 36", C > 5 T/m^ ddi vdi dap cd H > 30 m hoac (J) > 30^ C > 10 T/m^ ddi vdi dap ed H> 40 m. Qua ket qua the hien trdn hinh 9 va 10 thay rd miie do dnh hudng eua gdc ma sat trong ^ d^n he sd an toan Fs khi gia tang gdc ma sat trong thi he sd Fs tang len dang ke.
Khi chieu cao dap tuong ddi eao: trong cac nghien eiiu ddi voi dap cd chieu cao tii 50 den 70 m cho thay ro ddi vdi cac dap ed chieu cao H < 50 m thi cj) > 30", C > 10 T/m^ (Fs = 2,03), ddi voi eac dap cd H
< 70 m thi cj) > 36", C > 10 T/m^ (H - 60m: Fs-2,24, H - 70 m: Fs = 2,04) thi dap mdi dam bao dieu kidn an toan (Hmh8).
Hinh 7. Sa dd phan tich on dinh dap BTTL S anh hirong tdi 6n 2.2. Phan tich mOt sd nhan
dinh dap be tdng trpng luc
Khi nghien ciiu cac nhan td anh hudng tdi on dinh dap be tdng trpng luc, da tien hanh nghien ciiu cho gan 1000 trudng hpp khde nhau vdi 7 sen chieu eao dap, 3 seri dd ddc mdi dap (ehiSu rdng dap), 3 sen ve gdc ma sat trong, 5 seri ve lue dinh don vi, 3 seri ve chieu sau xir ly ndn.
Qua ket qua tinh toan nhan xet thay rdng: ddi voi nhimg dap ed chieu cao tuong ddi thap: 10 m, 20 m, miic dd anh hudng ciia cac ehi tidu co ly nen tdi miic dp dn dmh cua dap b nhiing miic dp khac nhau. Gdc ma sdt trong ctia dat n^n it cd dnh huong rat Idn den su an toan eila dap. Ddi vdi nen dat da toi rdi, cd lire dinh don vi nhd 0 -^ 1,8 T/m^ thi he sd an toan on dinh eua dap thay ddi khdng nhieu: Khi C - 0: he sd an todn dn dinh dao ddng trong khoang Fs- 1,023 -=•
1,56, C = 1,8 T/m^: Fs- 1,37 - 2,73. C - 3 T/m^: Fs
Hinh 8. Anh huong ciia chi tieu ca 1^ ddn he sd 6n dinh
Qua phan tich tinh todn, kdt qua tinh toan cho thdy ro rang rdng loai dat da rdi cd tinh dinh kem C<
1 T/m^ khdng phu hpp vdi dieu kien xay dung dap be tdng trpng luc. Trong tat ca cac trudng hpp tinh
50
KHOA HOC CONG NGHE
todn moi ciing chi ed trudng hpp gdc ma sdt trong ^
> 36", C > 1 T/m^ dap ung dupe dieu kien an toan dn dinh eiia dap be tdng cd ehi^u cao H < 10 m (Hinh 9).
thuan vdi viec gia tang chieu rong ddy dap B (Hinh 11).
Hinh 9. Anh huong cua chi^u cao dap tdi on dinh Ddi vdi nhiing dap co chidu cao khdng Ion H <
40 m, miic do anh hudng ciia chieu sau ddo hd mong cdng sau thi he so an toan Fs cdng tang len dang ke.
Su dnh hudng nay cang phat trien manh me eimg vdi su gia tang eua C va cJ). Tuy nhien su anh huong nay giam dan theo chieu cao ciia dap. Dap cang eao thi miie dp anh hudng ciia chieu sau dao mong cdng giam. Ddi vdi dap cd chieu cao H > 40 m thi Fs gan nhu thay doi tuyen tinh theo chieu sau xii ly mong (Hinh 10).
H-70m
Hinh 10. Anh huong cua chi^u sau mong dap tdi he s66ndinh
Ciing tuong tu nhu ddi vdi cae thdng sd khac, ddi vdi nhiing dap cd chi^u cao thap H < 40 m, chi^u rdng day dap B ed anh huong tuong ddi Idn den he sd an toan on dinh Fs. Vdi nhimg dap eo chieu cao trong khoang nay, miie dp anh hudng ciia ehidu rpng B ty le thuan vdi chidu cao H. Dap ed ehieu eao cang Idn thi viee mo rdng chieu rpng day dap B het sue eo y nghia trong viec gia tang dp an toan cua dap.
Ddi vdi nhiing dap cd chidu eao trong khoang 40
•T 70 m, he sd an toan dn dinh tang gdn nhu ty le
H-40 m H=70m
Hinh 11. Anh hirong ciia chi^u rdng ddy d?lp tdi h§ sd dndinh
Tir nhirng ket qua tinh toan phan tich cdc sen nghien ciiu, da tdng hpp va cd nhung nhan xet budc dau v6 anh huong ciia cae nhan td tdi he sd on dmh nhu sau:
Ddi voi dap cd ehieu cao < 20 m: He sd dn dinh Fs phu thupc chu yeu vao gdc ma sdt trong ^ eua nen. Chieu cao dap va chi^u sau chdn dap vdo n^n cd anh hudng rat Idn tdi he sd dn dinh. Khi sii dung phuong phdp phan thdi, neu nhu sii dung cac tidu chuan vat lieu theo diing he thdng tieu ehuan hien hanh tren the gidi thi ydu cau vd chi tieu nen tuong ddi cao C > 3,0 T/m^ (j) > 30".
Ddi vdi dap cd chieu cao ndm trong khoang 20 m
< H < 40 m: Miic dd anh hudng cua ehi tidu nen giam dan theo chieu eao. Luc dinh don vi C eua nen cang Ion thi anh hudng cita thdng sd gdc ma sat trong ^ den he sd dn dinh Fs cang Idn khi ehieu cao dap H tang dan. Gdc ma sat trong cua nen ^ cang Idn thi anh hudng cua lue dinh don vi C cua nen den he sd on dinh Fs cang Ion. Anh huong eiia chieu rdng day dap B den he sd dn dinh Fs cang Ion khi ehi tieu eo ly cua ndn 4), C cang Idn.
Ddi vdi dap co ehi^u cao 40 m < H < 70 m. Trong khoang chieu cao nay, miie dp anh hudng cua chi tieu ed ly nen i^, C den he sd on dinh Fs giam dan theo chieu eao dap. Anh huong den he sd dn dinh Fs ciia thdng sd gdc ma sdt trong ^ khdng nhieu bang anh hudng ciia lue dinh C khi ehieu cao dap tang len.
Khi chidu cao dap H tang len thi anh hudng eiia chidu sau chdn dap giam ddn. Anh hudng ciia chieu rdng ddy dap B den he sd an toan dn dinh Fs gan nhu tuyen tinh khi ehi^u cao dap gia tang.
3. K ^ LUAN
Thdng qua ling dung phuong phap phan thoi, sir dung phuong phap can bang cue han de khao sat cac nhan td vd dia chat ndn, kich thude dap cdng nhu
NONG NGHIEP VA PHAT TRIEN NONG THON - KY 2 - THANG 5/2019 51
iiin kien thi cong anh huong toi muc d6 on dinh cua dap be tong trong luc tren nen, da co nhung ket qua buoc dau ve quy luat bien doi he sd dn dinh cua dap be tdng trong luc khi co xet den su tuong tac giua mdi trudng ndn vdi nhau va gitia mdi trudng ndn va than dap. Nhung ket qua nay se mang tinh thuc te cao va cd y nghia Ion trong viec lua chon mat cat dap be tdng hop ly dam bao didu kien kinh te ky thuat.
Ket qua nghidn ciiu nay cung lam co sd cho cac nghl6n ciiu tiep theo trong van de xay dung tieu chuan dap be tdng theo quan diem tinh toan hien dai tiep can vdi ky thuat hen tidn tren the gidi.
TAJ UEU IHilM KHAO
1. Gravity Dam Design-US Army comrps of Engineers-EM 110-2-2000.
2. Gravity dam design - EM 1110 - 2 - 2200 cua Hiep hdi ky su quan ddi My (US Army corps of Engineer).
3. Quy pham thidt ke dap be tdng CHDl 2.02.02.85.
4. Tieu chuan thiet ke dap be tdng va be tdng <A thep 14 TON 56-88.
5. Tieu chuan ndn cac cdng trinh thuy cdnj TCVN 42-53-86.
6. Nguydn Van Mao (2008), Dap be tdng trooj luc. Bai giang sau dai hoc. 3 - 2008.
7. Nen dap phiic tap va cac van de ve ket cau no - Luc Thuat Nguyen 2000.
8. Hoang Minh Tii (2009). Nghien ciiu com nghe tin hoc phan tich dn dinh dap be tdng trong luc, Luan van thac si ky thuat 2009.
9. NguySn Quang Hung, Hoang Minh Tu (2009).
Xay dung cdng nghe phSn tich dn dinh dap be tonj trong lire theo tieu chuan Hiep hdi ky su quan dpi My. Tap chi Thdy loi va Mdi trudng sd 24- 3 - 2009. P
ANALYSIS OF SOME FACTORS AFFECTING STABILOY OF CONCEETE DAM Nguyen Quang Hung Summary
The research content of this article focuses on studying the method of extreme balance and application to stabilize the gravily dam concrete built on rock foundaUon and not stone. Through it, survey some factors such as dam height, dam width, cohesion force of the foundation, internal fnchon angle of foundation, depth of foundation buned... affecting stability of concrete dams on the ground. The research results give a clear picture of the change of dam stability coefficient according to basic parameters such as dam size, geological conditions, dam construction conditions. The research results are the basis for further research to improve the standard of concrete dam design.
Keywords: Gravity concrete dam, extreme balance, stability coefficient
Ngudi phan bidn: GS,TS. Tnrong Binh Du Ngay nhan b4i: 26/3/2019
Ng4y thdng qua phan bita: 26/4/2019 Ngay duy^t dang: 3/5/2019
