LtJ VUOT THIET KE vA CONG TRINH TRAN XA LU SU CO
TS. PHAM VAN QUdC, PGS.TS. PHAM NGOC QUY'
Tdm tdt: Cdng trinh thdo 10 eua hd chOa duge thiet ke vdi md hinh lu thiet ke va md hinh lu kiem tra da xdc dinh. Tuy nhien, trong thue te, nhieu trudng hgp da xdy ra 10 de'n vugt qud mirc theo tieu chuan thiet kd.
Nghien cOu IQ vugt qud tieu chudn thiet ke va cdng trinh trdn xa lu sir cd de ddm bao an toan cho dap vd ha du la nhiem vu khdng the thieu duge, dac biet Id ddi vdi eae hd ebOa ldn.
Thdng qua tdng kdt tinh hinh thuc te d Viet Nam, tham khao tdi lieu va kinh nghiem cua nudc ngoai, cac tdc gid trinh bay tinh hinh, nguyen nhan 10 vugt qud tieu chuan thiet kd vd mdt sd gidi phap edng trinh trdn thdo 10 vugt thidt kd, dam bao an todn eho dap chdn, hd chOa va ha du.
1. Tinh hinh va nguyen nhan lu vugt qua thiet ke
Chi tinh rieng hai dgt mua 10 cudi nam 1999, nhidu hd chOa, dap dang d mien Trung da xay ra mue nude vugt qud thiet ke, uy hiep nghiem trgng de'n an todn dap, nhu neu d Bdng 1.
Bang 1. Muc nudc lu d cac hd chua mien Trung thang 11 va 12-1999
77 Ten hd ehifa Mifc nudc lu vifot thiei ke
Dat la tif ngdy 02^10 thdng 11-1999 3
4 6 7 8 9 10 12 13 16
Tien Lang- Quang Binh La Nga-QuangTri Kinh Mon-Quang Tri Chau Son-Thua Thien-Hue'
Phu Bai- Thua Thien-Hue Dong Nghe-Da Nang
Hoa Trung-Da NSng VTnh Trinh-Quang Nam
Liet Son-Quang Ngai Hoi Son-
Vugt T.ke 0,4m VuotT.ke'0,7m Vugt T.ke 0,84m Vugt T.ke 2,05m Vugt T.ke 1,9m Vugt T.ke 2,36m Vugt T.ke' 1,46m Vugt T.ke 1,77m
Vugt T.ke 0,2m Vugt T.ke 0,1m Dot hi tif ngdy 02 den 06 thdng 12-1999
17 18
Cao Ngan-Quang Nam Phudc Ha-Quang Nam
Vugt T.ke 1.5m Vugt T.ke 1,6m
1.2. Dai hoc Thuy lgi.
2. Mdt sd yeu cau ddi vdi cdng trinh thao IQ vugt thiet ke - Kei edu khdng phOc tap.
- Md cua kip thdi kbi mue nudc hd ed nguy ea vugt qud mue nude 10 kiem tra de thdo nudc 10 khdn cap nhdm dam bdo an todn dap chdn.
- Thdo nude to ddng, hoae dd van hanh.
- Khdng gay ra sdng de doa den an todn dap chdn, dam bao an toan cho ha du.
- Chi phi ddu tu va ehi phi van hanh thdp nhdt ed the.
- Cd the phdi chdp nhan ban than cdng trinh thdo lu vugt qua thiet kd bi hu hdng mdt phan mdi khi boat ddng.
3. Mdt sd kieu dap tran sir cd thao lu virgt qua thiet ke 3.1. Trdn tu do
Tran tu do la loai kenh tran dao trong ndn ddt, dd tu nhien, cao trinh ngudng trdn bdng hoae gdn bdng cao trinh mue nude 10 thidt kd. Ket eau trdn tu do la mdt kenh hd, ddu kenh co gia ed mdt doan ngudng trdn dinh rdng dd khdng chd luu lugng, cao trinh ngudng tran thudng bdng hoae thdp hon mue nude 10 thiet kd.
Kieu nay ed the dp dung cho cdc hd chOa nhd, 10 kiem tra hoae lu qua tran su ed chenh khdng nhieu so vdi 10 thiet kd va d nhOng nai ed didu kien dia hinh, dia chat thuan lgi, nhu cd yen ngua thap, rdng va dai; ddt nen cd kha nang ehdng xdi tdt de giam khdi lugng gia ed.
3.2. Trdn sif cd dap ddt tu vd 3.2.1. Kie'u gia tdi hdng mfde
Dap dugc thiet kd d phia ha luu dinh dap cd tudng chdn nude, d day cd ldp kep cat tao mat trugt tren nen dap vdi he sd dn dinh thdp, khi muc nudc hd dat muc nudc Ifl thidt ke, node chay theo xi phdng dang ddn tren mat dap de gia tdi gay va dap, khi dap dat va vugt qua trang thai
can bdng cue ban thi dap tu vd. ' Dap tu vd kieu gia tdi bdng nude khi nudc trdn qua xi phdng cdn phdi cd thdi gian de v5
ddn va vd hei, vi thd kieu dap trdn nay tham gia thdo lu cham ban khi cdn thao nudc khdn cdp.
Khi ed su ed xdy ra thi khdi lugng tran hdu hdt bi phd hoai, do vay phdi ddp lai dap sau mdi lan
thao 10. i 3.2.2. Kieu ddn xdi
Co nhieu hinh thOe ddn node vd mai ha luu gay xdi, vi du dung xi phdng dat dudi dinh
dap, mieng eua vao ngang mue nude khdng chd d thugng luu. ' \ Dung dai de bi xdi trdi nen dOng eat hoae ddt ed tinh tan ra ldn dd lam khdi gay vd dap.
Qua trinh xdi gay vd dap can phdi ed thdi gian dd vd vd vd hdt nen tran tham gia thao lu cham. Khi cd so ed xay ra thi toan bd khdi logng xay dung trdn hdu hdt bi phd hoai, khdi lugng xay dung lai kha ldn va khd dap ung dugc nhiem vu ddn eon 10 tiep sau kip thdi khi su ed dien ra dau mOa 10.
3.2.3. Kieu trdn qua dinh
Vdi kieu nay dinh dap ddt tu vd thdp ban cao trinh mue nude 10 edn khdng chd thogng luu nhung neu qua nhieu nam khdng cd 10 vugt thiet kd, mdi ha luu nen chat, cd cay mgc nhieu. thi nhieu khi edn ddt khd bi xdi dd tu vd dap.
3.3. Ddp trdn cd nguang trdn zich gidc (Labyrinth Weir)
Cac dap tran be tdng trgng luc ed thd dOng hinh thOc ngudng tran zich gidc kidu phim dan Piano de tang ehieu ddi thue te tran nude, do dd tang duge luu lugng thao nude, giam duge mue nudc lu trong hd.
3.4. Trdn su cd cd cua van tu dgng lat true ngang
Cua van tu ddng lat gdm mdt tdm phdng quay quanh true ndm ngang. Tran su cd it lam viec. vdi yeu eau gia xd 10 nhanh khi edn thidt, thi cua van tu ddng lat rdt thich hgp.
Nhugc diem ldn nhdt la thudng xdy ra hien tugng va dap khi eua ddng. md va rung ddng khi cua lat ndm trong ddng ehdy ddn den hu hdng eOa. Mat khac, can chO y den cac tac ddng bdt lgi khi thdo 10 dot ngdt vdi luu lugng ldn ddi vdi hd chOa, eOng nho ddi vdi phia ha luu.
3.5. Ddp trdn cd cua md nhanh - Flash Board
Tren ngudng dap dat he thdng ede tdm phdng chdn nudc ed chieu cao tren dudi 1 met. Khi muc nudc 10 trong hd chOa vugt qua mdt gidi ban nhdt dinh. he thdng ban va cdt dd bj gap nhanh xudng va bi pha hoai todn bd, nhd dd thao 10 khdn cdp cho hd chOa.
3.6. Dap trdn cd bg phdn cdu ehi
Ddi vdi ede dap be tdng trgng luc ldn, dOng hinh thOc khdi edu ehi bdng be tdng dd thdo 10 khdn cdp la rdt khd thi (Hinh 1).
Dudi day khdi edu ehi la khe hd, ddng thdi ldm vat dem chdn nudc khit d cudi ehan de de lgi dung ap luc ddy ndi cua nudc. Khi muc nudc 10 trong hd chOa vugt qua mdt gidi ban nhdt dinh, khdi cdu ehi bi lat nhanh xudng, nhd dd thdo 10 khan cap cho hd chOa. Sau mdi lan hoat dgng, edn phdi khdi phuc lai khdi cdu ehi. Cac khdi edu chi cd the ed kich thude nhu nhau hoae khdc nhau, ede tdm nhd lat trudc, cac tdm ldn lat sau. Cde tdm de lam, de kiem tra. Cd hai kieu: kieu bdn phdng va kidu dap Zich gi'c. Cac cua van nay duge giO tren mat dap bdi cac khdi gia tdi. Mdi cua van duge edu tao bdi ba bd phan: mdt pheu chOa nude dugc lam bdng kim loai hoae be tdng edt thep, mdt ban day va mdt d'ng thu nude dugc ndi vdi khoang (budng) thao nudc d dudi day. De gidm su tich nudc vao trong khoang, mdi khoang bd tri hai rinh thodt nudc. Khdp ndi giOa hai cOa van lien ke nhau duge bit kin bang mieng dem cao su phdng del.
Khoang chijra ni/dc
Dem cao su Thanh chong Thanh giang
dng thu
nU'dc -^Oinh ong
thu ni/dc
Thanh gilng ngang (cimg)
Gdi
Di/dng tran Mieng dem
khit ni/dc
Hinh 1. Cac bd phan ciia cau chi
6 Phap, eua van lat dugc cung cap vdi ba loai hinh dang tieu chuan: NHL, WLH va WHH dua tren ede kdt qua nghien cuu eua Phdng thi nghiem thuy luc qud'c gia (NHL) d Chauton, Phdng thi nghiem d Norris Tennessee (TVA). Bd rdng mdi cira cdu chi tir 1,5 m de'n 6 m.
4. Cac bien phap khac de phdng chdng lu virgt thiet ke 4.1. Ddp con trach ndng cao them dinh ddp
Nang cao them dinh dap to 0,5 den I met bdng con trach ddp dat, tudng be tdng, da xay, hoae rg dd ed ehdng thdm. Ddng thdi cd the edn nang cao them tudng ben dap tran. Bien phap nay tang them duge dung tich hd ehua, do vay giam dugc nguy ca nudc lu tran dinh dap. Tuy nhien, cdn kiem tra lai an toan, dn dinh ciia dap khi thuc hien bien phdp nay.
4.2. Gia cd dinh, mdi dde vd chdn ddp hg luu
Trdng ed hoae cdc gia cd bdng bien phdp khdc de bao ve dinh, mai dd'c va ehan dap ha luu se eho phep nudc 10 trong hd chOa tran qua dinh vdi mdt muc do nhat dinh. Bien phap nay thich hgp vdi cde hd, dap nhd.
4.3. Gidi phdp phdi hgp
- Cd the vua nang cao dap vOa dap trdn cdu chi, dap trdn zich gidc.
- Hoae vOa gia cd dinh, mdi dap, ehan ha luu vira md rdng tran... ,, ; 5. Mdt sd nhan xet va kien nghi
- Tu cde nguyen nhan gay ra 10 vugt thiet ke neu tren, chung ta cd the xem xet khdc phtic
timg vdn de dd han che va phdng chd'ng muc nude 10 vugt qud mOe thidt ke', de doa an todn dap chdn va cdc cdng trinh ddu mdi.
- Mdi loai hinh thOe thdo IQ vugt thiet kd ddu cd uu, nhugc diem va didu kien su dung nhai dinh. Viec lira chgn hinh thOc ndo phai dua tren dac diem rieng eu the eua timg hd chua.
- Mdt sd hinh thOc cdng trinh de thdo lu vugt thiet ke neu tren da dugc dp dung ed hieu qua d nhieu nudc tren the gidi nhu: dap tran ed bd phan cdu chi, dap trdn ed ngudng zich gidc kieu phim ddn Piand, tdm gap nhanh.
- Ddi vdi nude ta mdi bude ddu dp dung edng trinh thdo 10 vugt thidt ke', vi thd cdn nhieu van de can tiep tuc nghien cOu vd thdo luan.
- Cho de'n nay, ehOng ta da xay dung gdn 5.000 hd ehua. Cdn xdc dinh lai nang lire eua cong trinh thdo 10 cho cde hd chOa da xay dung. Mat khdc, phdi xem xet ede gidi phdp de phdng chdng 10 vugt qud mOc thidt ke.
- Ddi vdi ede hd chOa dang trong qud trinh xay dung can tinh toan thidt ke edng trinh thdo lu theo tieu chuan phdng chd'ng 10 TCVN 285-2002, ddng thdi cQng edn phdi xem xet cdc gidi phap de phdng chd'ng lu vugt qud mOc thiet ke ngay tO eac bude chudn bi ddu tu.
TAI LIEU THAM KHAO
[1] Pham Nggc Quy, Pham Van Qude va nnk: "Nghien cuu tdng quan 10 vugt thiet ke d cac hd chOa nude va de xudt giai phdp trdn su sd thieh hgp cho an todn edng trinh ddu md'i", Bao cao khoa hgc de tdi cap Bd, 2003.
[2] Vien Nang lugng: "Bdo edo ket qua nghien eOu tran su cd sdng Hinh", 2000.
[3] Cue qudn Iy nude va Cdng trinh Thuy lgi - Bd Ndng nghiep va Phat trien ndng thdn:
Tinh hinh dam bdo an todn cac hd ebOa cua cdc tinh tO Qudng Binh den Binh Dinh", Tgp chi Thuy lgi, sd 331, thdng 12-1999.
[4] Hd so thiet kd trdn xd IQ sir cd sdng Hinh - Cdng ty Tu vdn Xay dung Dien I.
[5] Hd so thidt ke trdn xd 10 su cd hd chOa nude Ke Gd - Cdng ty Tu van Xay dung Thuy lgi I.
[6] Hd so thidt ke trdn xd lu su ed hd ehua nudc An Ma - Cdng ty Tu van Xay dung Thuy lgi tinh Quang Binh.
[7] The Design Flood Guidelines: International Commission on Large Dams, 12-1990.
[8] Henry T. Falvey, Member, ASCE, and Philippe Treille: "Cdc van de vd thuy lire va thiei ke eua su ed ", Tap chi Journal of hydraulic engineering, 7-1995.
Summary
Spillways are usually designed with the determined flood models for releasing the exceeding water to ensure the safety of dams, reservoirs and downstream regions.
However, in the fact, there are may cases, in which the coming floods are bigger than the designed flood models.
Study of the over designed floods and emergency spillways for ensuring safety of the dams, reservoirs and downstream is our indispensable duty, especially for the large reservoirs.
Based on the technical investigation of practical existing conditions in Vietnam, references on the documents and experiences of foreign countries, the authors present the practical situation, reason of the over designed floods and the structure solutions discharging the over
designed floods to ensure the safety of dams, reservoirs and downstream regions. ,„,,
