Kết quả nghiên cứu xói nở bờ sông hồng khu vực thành phố lào cai

32(4), 357 364 Tap chf CAC KHOA HOC VE TRAI BAT 12 2010 KET QuA NGHIEN CUU XOI Ld BC) SONG HONG KHU VUC THANH PHO LAO CAI NGUYEN DANG TUC, NGUYEN VAN HU(5NG I DAT VAN DE Thinh phd Lao Cai nim d hai be[.]

32(4), 357-364 Tap chf CAC KHOA HOC VE TRAI BAT 12-2010 KET QuA NGHIEN CUU XOI Ld BC) SONG HONG KHU VUC THANH PHO LAO CAI NGUYEN DANG TUC, NGUYEN VAN HU(5NG I DAT VAN DE Thinh phd Lao Cai nim d hai ben bd sdng Hdng, dang dupc quy hoach vi xay dung Nai day cd cua khau Qud'c te, khu thuong mai Lao Cai Cac tuyen dudng giao thdng : dudng sit Ha Npi - Lao Cai, qud'c Id 4D vi dudng Hoang Lien ; dudng cao td'c Ha Npi - Lao Cai dang dupc thi cdng Cac cdng trinh diu nim d hai bd sdng Hdng, vi vay, xdi Id bd sdng Hdng gay anh hudng rat ldn den cupc sdng cua nhan dan dja phuang va su phat trien giao thong, cong nghiep, nong lam nghiep, du lich cua thinh phd Lao Cai De xac djnh nguyen nhan, ca che gay xdi Id bd sdng Hdng thupe phd Lao Cai, chdng tdi da thu thap, phan tich tai lieu dja chit, kien tao, trim tfch, khoan, dja chin khuc xa, dia chat cdng trinh, dja chit thuy van ; sd dung chudi sd lieu tde dp ddng chiy lien tue tren mat cit ngang tram thuy van Lao Cai (phfa luu ciu Cdc Leu khoang 300 m) thdi ky mua lu, nham phan tfch nhung diln bie'n ehe dp thuy van - thuy luc song ngdi nhung nam gin day lien quan tdi qua trinh xdi Id ; phan tfch anh miy bay, anh ve tinh vi khao sat thuc dja, nham xac djnh dja hinh diy sdng, danh gii su phan bd cic loai trim tfch diy sdng, dac tfnh Idng din, cac yeu to thuy - thach dpng luc va vai trd cua chung qui tnnh xdi Id bd song Hdng d khu vuc nghien cdu II KET QUA NGHIEN CUU / Hien trgng xdi la bd sdng Hong a) Xoi la hai bd song doan tif nga ba song Nam Thi den cau Pho Mdi - Dcic diem diet hinh ncri uiy xoi Id : khu vuc xdi Id nam tren dja hinh thim tfch tu kha bing phing cd dp cao so vdi muc nude bidn 90 - 100 m Them sdng bd phai sdng Hdng dupc ciu tao chu ye'u bdi tram tfch De Td bd rdi vdi phan la sdi, san, cat, set cd ngudn gdc sdng va san pham phong hoa td da tram tfch Neogen Thim sdng bd trai sdng Hdng ciu tao chu ye'u bdi trim tfch bd rdi vdi phin chu yeu li cat, set cd ngudn gd'c sdng aQ.y - Dien hie'n : hang nam d hai ben bd sdng Hdng tu ciu Cdc Leu den ciu Phd Mdi diu xiy xdi Id manh Ke be tdng bd phai td nga ba song Hdng sdng Nam Thi den ciu Phd Mdi da hoan thanh, ke be tdng phia bd trai sdng Hdng vin dang tiep tijc thi cdng - XII the : doan da dupc xay dung ke be tdng, cho nen hien tupng xdi Id hai bd sdng Hdng da dich chuyin vl phfa luu Vj trf xdi Id manh nhat va gin nha't la khu vuc trudng hpc xa Van Hoi b) Xoi Id bd song doan tir khu vi/c trudng hoc xa Van Hoa den Ngdi Xum - Dac diem dia hinh neyi xdy xoi Id : khu vuc xdi Id nam tren dia hinh thim tfch tu kha bing phing Thim sdng dupe cau tao chii yeu bdi trim tfch bd rdi vdi phin chu yeu la cat, set cd ngudn gd'c sdng aQ,v - Dien hie'n : sau xay ke be tdng phfa thupng luu, vj trf lien tuc bj xdi Id vdi tde dp rat nhanh, udc tfnh khoang 10 m/nam Khu vuc xdi Id keo dii phuang tay bic - ddng nam khoang 150 m, cao trung binh m, ddi nai cao den - m, an sau vao bd khoang m, vich dd'c gin thing dung (70-80°) Phfa tren la rupng Ida, cay an qui lau nam va hoa miu, dae biet cd trudng hpc d gin sat vj trf xdi Id - Xii the : vin dang cd xu the tie'p tue xdi Id, dac biet vio mua mua ddng ehu luu chiy vao bd sdng Ngoai ra, xdi Id cdn xay manh me d cae khuc udn cua bd sdng, nhu khuc udn d bd trai sdng Hdng, 357 phfa tren cua Ngdi Xum, each dudng sat Ha Npi Lao Cai khoang m hoac xdi Id d khuc udn bd phai sdng Hdng, phfa dudi cira Ngdi Dum Cdc yeu to lien quan den xoi Id bdsong Hong a) Yeu to dia mao Ye'u tddia mao lien quan den xdi Id d hai bd sdng Hdng quan trpng nhi't la dp dd'c bd sdng O cac khu vyc xdi Id, bd sdng deu cd dp dd'c Idn Chung thud'ng cd hai dang mat cit: 1) bd sdng d phfa tren mat nudc (tiep giap vdi sudn nui) cd gdc dd'c 30-35°, phin dudi mep nudc cd gdc dd'c 45 - 55° ; 2) bd sdng phia tren mat nude cd dp dd'c ldn (60 - 85°), cao trung binh - m, cd noi din - m va sudn day sdng CO dp ddc 45 - 50° Xem xet cac diem xdi Id bd sdng Hong d phd Lao Cai cho thiy, xdi Id khu vuc Ngdi Xum, nai cd dudng sit Ha Npi - Lao Cai chay qua, cd mat cit bd song thupc.ldeuj va khiLvuc-Xoi Id thein_ song bic khu vyc Phd Mdi, xa Van Hoa cd mat catbdt sdng thupc kieu Vdi dp dp'c ldn nhu tren, bd s6ng rit d i bi xdi Id, ke ca miia nudc kiet b) Yeu to dia chat ® Thdnh phdn vgt chdt - Dit bd sdng khu vyc xoi Id la dit cat pha set, dit set miu niu, nau sim, dang deo udt va dit phong hoa bd rdi ; be day theo so lieu dja chin khuc xa khoang - m [3] Cdn b them bac sdng Hong chii ye'u la cat hat trung, cat pha set, miu niu sim - Trim tfch ting mat long din sdng Hdng doan phd Lao Cai, gdm : Cat hat trung : cd dudng kfnh trung binh (Md) dat 0,3-0,4 mm, phan bd chii yeu d hai diu khu 'vyc doan bd dang bi xdi Id Cat hat nhd : cd ducmg kfnh trung binh (Md) 0,22 - 0,26 mm, phin bd chu ye'u d hai dau bai boi noi giira Idng song Bpt: trim tich bpt phan bd rpng d long din Dudng kfnh trung binh ci'p hat nam khoang 0,01 - 0,1 mm the hien vai trd dpng Iuc b day thay doi kha nhanh Set : dudng kfnh trung binh cip hat nim khoang 0,006 - 0,06 mm Trim tfch chi gap d day true Idng din doan dudi ciu Cdc Liu keo dai khoang 0 - 0 m [31 358 ® Cdc dirt gdy kie'n tgo Thanh phd Lao Cai nam ddi ddt giy Sdng Hdng d hai phia trai va phai sdng Hdng, cd nhieu ddt giy, cd chd chay sat bd sdng {hinh 1) - Ddt giy d phia trai nim sat bd sdng, cit qua cac khu vyc xdi Id cd cau tao tir da bien chit thudc phdc he sdng Hdng d Van Hoa, ngdi Xum va cac khu vyc xdi Id cd ca'u tao td da Neogen - De Td d khu vyc Phd Mdi, khu vyc trudng hpc xa Van Hoa [6j - Ddt giy phi'a phai nam sat bd song b cac khu vuc xdi Id cd ciu tao td da Neogen - De Td nhu phudng Cdc Leu, ngdi Dum, Xuin Tang Cac ddt giy nim sat bd song da Iam cho ke't ciu cua bd va tinh chit ca Iy ciia dit da ciu bd sdng yeu hin di: da gd'c cd bi phi buy dl thim nudc, tao ntn ting phong hoa diy bd rdi, da - dit tfch tu Holocen va Hien dai gin kit yeu, dp thim nudc tang, d a d o bdsPng-carrgtH brxoi Id (D Tinh chdt co ly cua ddt dd Bd song d khu vyc xdi Id cd hai loai dit da : da Neogen bj phong hoa yeu d phfa dudi va di't phong hoa bd rdi, di't dip, trim tich sdng d phia trfen [6] : - Cac da Neogen bi phong hoa yeu, phin bd b dudi siu ; co dp ben, dp on dinh thip ; dp bien dang, dp ngirn nudc cao, thudng bi niit ne Chung cd dd chat vda (2,2 - 2,65 g/cm^), dp rdng 10 - 15 %, chda i m ft Yiq ngi'm nudc thay ddi theo dp khe nut va dp phong hoa He so thi'm > 0,5 m/ng.d Sde chP'ng nen < 25 kg/cm^, va sde chd'ng cat < 10 kg/cm^ - Nhdm dit phong hoa bd rdi, di't dap va tram tfch sdng phin bd bd sdng xdi Id Day la nhdm dit bd rdi vi mem dfnh Thanh phan la cat hat trung, cat pha set, set Tuy theo hat, chung tao nhdm dat bd rdi hoac mim dinh Dac trung ciia nhdm la tfnh chit ca ly bie'n ddi pham vi rpng Loai dit bd rdi cd h6 sd thi'm ldm, di't mem dfnh (set) chda am, khdng bi hoa tan, he sd thim thudng nhd ban 0,1 m/ng.d Dp dfnh ke't 0,11 - 0,24 kg/cml £)q bao hoa nudc 80 88 % Thanh phin dp hat chii yeu 0,01 - 0,05 mm Gdc ma sat 10 - 160 He sd nen lun 0,02 0,05 cm^/kg [5] Nhu vay, be diy ldp dit phong hoa bd rdi Idn, vdi tfnh chit dja chi't cdng trinh nhu tren, rit dl gay xdi Id bd sdng Hinh Sa dd ciu true tan kien tao va hien trang xdi Id bd sdng Hdng phd Lao Cai CHO GIAI : Khd'i nang Po Sen, Khd'i nang nui Con Voi, Khd'i sut Lao Cai, Ddt giy chinh va hudng dich trupt, Dut giy phu : a) xac dinh, b) gia dinh, Ddt giy thuan, Ranh gidi Tp Lao Cai, Dudng ddng mdc, Bien gidi, 10 Dudng sit, 11 Dudng bp, 12 Xdi Id bd sdng ® Nguon nifdc difdi ddt Nudc dudi di't khu vuc xdi Id bd phai sdng Hdng chda cac ting di't da Neogen va Holocen - Ting chda nudc Holocen la ting chda nudc lo hdng, phan bd d thinh phd Lao Cai va dpc theo hai b6n bd sdng Hdng Thanh phin thach hpc la cupi, soi, cat hat thP xen Idp set mdng td 0,3 den m, thudc tudng long song, bai bdi Khu vyc phd Lao Cai cd nam gieng khoan khao sat dia chit cdng trinh xuyen qua ting Dp diy ting chda nudc phu thudc vao dja hinh day, bien ddi td 8,7 m (gieng khoan 10) den 11,4 m (giing khoan 8), trung binh 10m[l| Nudc dudi dit ting chu yeu la nudc khdng ap hoac cd ap ye'u, ngudn cung cip la nudc mua va nudc sdng Sy dao dpng ciia myc nudc ngim rat Idn, phu thupc theo mua Mua kho, myc nudc ngim nam sau td 1,2 den 1,8 m, cd nhung nai gap d chieu sau ldn ban Mua mua, myc nudc ngim d khoang 0,5 m, ddi nam sat mat dat, hoac chiy mat dat ddng Ve mua khd, luu lupng cac mach Id hoac gieng dao dao dpng td 0,5 den 1,0 //s, ty Ie luu luong gieng bam dat 0,5 - 1,0 //sm, trung binh la 1,0 //sm Nudc dudi di't chda ting Holocen d khu vue xdi Id bd sdng, thudng nim rit ndng, td 0,5 den m so vdi mat dat, cd chiy ddng, lam cho dit bi xdi ngim phfa dudi bd sdng Nudc dudi dit d day Iam cho dit ngam nudc dat den 80 - 88 %, lim yeu tfnh ca ly cua dit, gay xdi Id bd sdng 359 - Tang chda nudc Neogen la ting chda nudc Id hdng - khe nut Thanh phin thach hpc la cupi kit da khoang, cat ket gin kit khong rin chic, xen ke la cac ldp mdng bpt kit va cic thau kfnh than nau Chung phan bd dpc sPng Hdng, Id d khu vyc dai Phat - Truyen hinh tinh Bl diy eua da Neogen td vai chuc met den hang tram met Myc nudc tTnh ciia cae giing thudng nim cich mat dit 5,5 - 6,5 m, ddi cd ngudn ty chay Luu lupng nudc gieng dao nhd, dao dpng td 0,01 den 0,3 //s Ngudn cung cip nude cho cac tang chda nudc la nudc mua va nudc ddng chay VI mua mua, cac gieng diu nhieu nudc, nhilu nai nudc chiy trin tren mat da't Ve mua khd, cac gieng deu ft nudc, myc nudc ngam bj thap Ting chda nudc Neogen va Holocen d khu vyc dai liet sy, dai Phat - Truyin hinh cd hudng ddng chiy xudng song Hdng, gay xdi ngim, lam eho tfnh chit ca ly cua dit da d day bj giam yiu manh Chung la tie nhan cpng hudng gay xdi Id bd phai sdng Hdng d khu vuc Yeu td thuy - thach dgng luc a) Bien dong mua va lu tai Lao Cai Lupng mua d khu vuc phd Lao Cai tuang ddi ldn, trung binh 1.800 mm/nam Mua mua thuang keo dai thing, bat diu td thing IV, ke't thuc vao thing X Mua ldn tap trung vao thing VII, thing VIII Su dao dpng lupng mUa hang nam khdng ldn He sd bien dpng (gia tri phin tram dao dpng so vdi tri sd trung binh nhilu nam) la 0,21 Mua mua cd lup'ng ddng chiy binh quan chiem tdi 12 -15 % tdng lupng ddng chiy c i nam Lupng ddng chay nam vdi modul ddng chiy thing Idn nha't dat tdi 50-100 //skm' Thing VIII cd lupng ddng chay Idn nhit nam (chiem 15 - 20 %), cung la thdi diem gid mua Ddng Nam cue thjnh tai khu vyc vdi nhilu dang nhilu dpng thdi tiet dac biet bao, ap thip nhiet ddi va dai hpi tu nhiet ddi cd kha nang gay mua ldn tren dien rpng Thdi ky thudng cd lu ldn, ddi luu Iupng nudc va dp cao dinh lu dat tdi cac gia trj cue doan {hdngl) Theo ket qua dac tai tram thuy van Lio Cai vio cac thing mua lu td thing VI din thing X tdc ddng chay trung binh cd gii trj td 1,3 den 2,7 m/s va vao cac thane VII - IX cd thi ldn han m/s 360 Bdng Luu lUdng d o n g chay I6n nha't quan trae duoc tai tram Lao Cai [7] Omav tjmax i^'/c\ (m /s) TT,;^ • Luu luonc Q, m / s tuang dng hot sian - ' ? - - i • - „ ec: \ V -,u-tan suat xuat hien p(Vc) xuat hien —^-= '—^—— 5% 10% 5% ' I% 8.430 19/8/1971 7.140 5.500 4.860 4.010 b) Dac diem phan bo va hinh thai Idng din Doan sdng Hdng chiy qua phd Lao Cai cd chilu dai khoang 20 km kl td Kim Thanh den het dja phan phd Ldng din cd phuang tay bic - ddng nam, dp rpng Idng song trung binh dat 300 - 400 m, chd rpng nhit (tai nai dang diln qui trinh xdi Id manh phfa bd phai) dat xip xi 600 - 700 m, dp ddc Idng sPng ldn, xip xi 1° (td ciu Cdc Leu den cira Ngdi Dum dai khoang km cd dp chenh cao tdi m) Tai khu vuc nghien cdu, doan bd trii td Phd Mdi den khu vyc trudng hpc xa Van Hoi va bd phai song d phudng Cdc Leu cd cau tao chil yeu la cat va phd sa sdng, la khu vyc rat de hi xdi Id vao mua lu, nudc sdng dang cao va ddng chiy manh Ldng sdng thdi dilm khao sat vao mua ddng tuang dd'i can Phfa bd phai sdng tdn tai cac bai thoai, dp sau trung binh khoang 1,5 2,0 m Tram tfch b l mat chu yeu la cat nhd hat mjn, nhan dan dja phuang dang khai thic lam vat lieu xay dung True long din song nim sit bd trai td ciu Cdc Leu den diu bai Soi Tiln vdi dp sau dac td den m, sau dd ddi hudng sang bd phai nam sat true dudng Hoang Lien - Bach Ding, tao hd xdi sau, vdi dp sau trung binh - m vi cho sau nhit dat m Mac du vao mda khP, tai lach nudc sau nudc chiy tap trung, van td'c vin dat xip xi 0,7 m/s [3J Trong qua trinh phit trien cua sdng, hien tupng xdi-bdi phit trien long din la quy luat ty nhien ciia ddng sdng xu the "tu dieu chinh" de lam giam dp dp'c cua mat nudc Mpt trang thii can bang dpng gida td hop nudc - cat bun - hinh thai ldng din bj pha vd, hien tupng phat triln Idng din mdi se diln ra, dudi tic dpng cua nhilu yeu to Cd the gpp cac yeu td tic dpng hai nhdm chfnh : diiu kien ngoai sinh (dao dpng myc nudc, bien dpng luu lupng, ddng bun cat, c h i dp mua am ), dieu kien npi sinh hay mat dem dja chat (hoat dpng kiln tao - Tan kien tao chuyen dpng dja dpng luc, phan bd ldp trim tfch De Td, boat ddns cua nude ngim) Qui trinh phat trien tu nhien cua Idng din sdng ngdi (goi tit la qua trinh long din) thudng diln thd ty theo chu ky [2| : - Udn cong ban che, - Udn cong khdng hoan thien, - Udn cong hoan thien, - Chay eat thing, ket thuc mpt chu ky phat triln long din Tai phd Lao Cai, khdng gian udn khuc long sdng Hdng tren viing ndi bj gidi han bdi nin da cdng, nen nhin chung tai khu vuc qua trinh udn khde kit thuc sdm d giai doan udn cong han che, tren mdt ddi trim tfch De Td kha hep Tai khu vuc hien tupng Idng sPng xdi sau d mpt sd nai da phat trien den nin da gdc, bupc ddng nudc phai thay ddi hud'ng chiy Tren khu vyc ldng din sdng Hdng td cua ndi ddng Nam Thi tdi nam bai Soi Tiln dii 2.500 m, cd hai doan bd dang bj xdi Id manh trung vdi hai khuc cong lien tiep : - Khuc cong thd nhit ben bd trai, doan td gin ciu Cdc Leu den phfa dudi khoang 300 m vdi ban kfnh cong Rl = 500 m - Khuc cong thu hai ben bd phai vdi vj trf dang bj xdi Id manh nim kl doan dudng Hoang Lien Bach Ding vdi ban kfnh cong R2 = 650 m Vdi bin kfnh udn cong hien tai chua ldn so vdi dp rpng trung binh cua Idng dan, Idng sdng cdn tiep tuc udn khuc de dat tdi qua trinh udn cong hoan thien, sau dd md'i chuyen sang giai doan chiy eit thing Din ve phfa luti, xuit hien cic kliuc cong khie cd ban kfnh nhd bj han cbl bdi nen da cdng ffliu vay, dieu kien td'c dp ddng chiy manh tren nin trim tfch De Td yeu, qua trinh xdi Id vin tiip tuc phit triln d hai bd sPng Hdng, neu khong ed cie giai phap cong trinh nham giam bdt qua trinh phi huy bd Hien tupng xdi Id bd sPng Hdng cd anh hudng ldn tdi dp an loan cua cac cong trinh xay dung tren true dudng Hoang Lien - Bach Dang, dudng sit Ha Npi-Lao Cai (3] c) Td'c va luu lUdng ddng chay Tdc dp va luu Iupng ddng chiy sdng Hdng cd anh hudng ldn din su xdi Id bd va xdi mdn day sdng Kit qua dac tai tram thuy van Lao Cai cho thay td'c dp va km lupng ddng chay phu thupc theo mua Mua kiet, muc nudc va luu lupng thap, ddng song tap trung d phin sau nhat cua long sdng Tdc dp ddng chay trung binh td 1,1 den 1,8 m/s dat cue tilu 0,7 m/s, luu Iupng 256 mVs Mua lu, muc nude sdng va luu lupng nudc tang cao, ddng sdng tran diy ea long va lam ngap chim gin het bai bdi Ddng chay vdi td'c dp trung binh td 1,3 din 2,7 m/s, dat cue dai > m/s Luu lupng ddng chiy dat cue dai 3.000 8.400 mVs, dat cue lieu 90 mVs Khi td'c dp ddng chiy tang cao, luu lup'ng nudc ldng sdng ldn se gay ddng chiy rd'i manh, lam xdi Id bd va xdi mdn day sdng Tlieo kit qua thuc nghiem va tfnh loan, tdc dp ddng chay gay xdi id ty le vdi kich thud'c cua vat lieu {hdng 2) Bdng Toe dong chay cue dai khong gay xoi Id Dit da Tang lan va da hpc ldn Tang lan va da hoc nhd Cupi va da dam ldn Cupi va da dam nhd Sdi vi san sdi Tdc dd (m/s) 4-5 3-4 2-3 1-1,25 0,6- Cat hat thd va hat Idn Cat hat vda va hat nhd Cat hat mjn Set va set pha cat chat Set va set pha cat kem chat 0,26 - 0,35 0,2 1,2 0,5 0,6 - 0,8 Cat pha set chat Cat pha set kem chat 0,25 - 0,35 0,20 - 0,30 Theo kit qua thf nghiem va khao sat, bd phii sdng Hdng, gin dai liet sy, ehu yeu la dit phong hoa bd rdi, da't dap vdi phin dp hat chii yeu li set, set pha cat va cat, kfeh thude hat tu 0,25 din 0,5 mm, xen lan mpt sd sdi, san 'Hianh phin vat chat d bai bdi va thim sdng chu yeu la cat hat trung, hat nhd, bpt, set, vdi kfeh thudc hat < 0,5 mm Tren ca sd phan tfch ham lupng phan tram cap hat, dudng kfnh trung binh, dp chpn lpc, dudng cong tfch luy va dien phan bd ciia phin vat chat d khu vyc xdi Id bd sdng gin dai liet sy va dd'i sanh vdi td'c dp, luu lupng ddng chiy cd the thay hien tupng xdi Id bd va xdi sau long din d day xiy c i vao thdi ky mua Id va mua kiet Td'c dp ddng chay va luu Iupng nudc d doan sdng xdi Id cdn tao ddng chay rdi ldn gay tfch ttj tram tfch d bai ndi giua sdng va khu vuc ngdi Xum, lam thay ddi qua trinh long din, hudng ddng chay vao bd sdng ddi dien, cang tang cudng muc dp xoi Id bd sdng Hdng {hinh 2) 361 a) ngupc lai, ket hpp vdi ddng chiy dpc tao nen ddng chiy rdi phdc tap Iam xdi mdn bd va day sdng [78A Gpi V la van td'c cua ddng nudc d Idp sat day va Vkd la td'c dp khdi dpng giy but phi cac hat biin cat d day Khi td'c dp ddng chiy V thay doi, -vupt qua tdc dp gidi han cho phep khong xdi Vkd se xay cac trudng hpp sau day : '74 c> 'voc h72 ,*:r>^^ '^^-vr-^-"'" 50 100 Tf^Ngay 23-8-1996 H H ==78,84 m Q = 1.970 mVs Khoang each (km) 150 200 b) V < Vkd : bun cit day khdng chuyen dpng, Idng din khdng thay ddi V > Vkd : cac hat bun cit chuyen dpng rieng re d trang thai Ian d Idp sat day sdng 76 -\>\S,3 74 V •» Vkd : biin cat bi but khdi day va chuyen ddng rd'i vdi khd'i lupng Idn d trang thai la limg / 784 4.,^ r "*''^ \* •'•? a-J^ Ngay 25-8-1997 H = 77,30 m Q = 1.070 mVs Khoang each (km) ^?f-^ :;^j H|Z 72 too 50 200 150 c) '\ 76 \ \ ^ •74 V"~ # • - •-2 5-* :1fef?^''^'^ •Jt ,r- - J C C ^ - ^ ' ^ ^ >TTTn-rt^''' 72 Ngay 26-7-1998 H = 79,44 m Q = 1.920 m'/s Khoang each (km) 50 too 150 200 Hinh Phan bd td'c dp ddng chiy tai mat cat tram thuy van Lao Cai (V, ms) [31 d) Cac qua trinh Idng din Cac qui trinh long sPng lidn quan den xdi Id bd sdng la qua trinh xdi sau va xdi ngang Qua trinh ehi xiy tdc dp cua ddng nudc d Idp sat diy tao lyc diy Iam di chuyen cac hat bun cit d day (gpi la tdc dp tdi ban) Khi tdc dp ddng chay Idn ban nhilu so vdi tdc dp tdi ban, vat lieu day sdng se tham gia vao chuyin dpng rdi ciia ddng nudc va gay xdi Id manh me b l mat day sdng Tai khuc udn cua Idng sdng d mat tiet dien ciia ddng chay, xuat hien ddng ngang, d tren mat thi hudng td bd Idi sang bd Idm, d dudi day thi 362 Khi td'c dp ddng chiy tang len vupt qua kha nang khang xdi cua vat lieu day sdng, xiy qua trinh biit phi cac hat rieng re Khi tdc dp ddng chiy ldn ban nhieu so vdi tdc dp khdi dpng cua cac hat bun cat, vit lieu day song se tham gia vao chuyen ddng rd'i cua ddng nude va giy xdi manh me b l mat day sdng Ngupc lai, tdc dp ddng nudc giam di khdng dii sde day, cic hat bun cat la limg rieng re se rai din xudng, giy ling dpng Nhu viy, qua trinh chuyen vin cua bun cat ddng nudc dupc chia Iam hai trang thii : - Trang thai di day hay chuyen ddng lan td td theo ddng nudc d ting sat day (khi tde dp chiy tha'p), - Trang thai la lirng hay chuyen dpng rdi ddng nudc (khi td'c dp ddng chay dat gia tri cao) Trang thai di diy gin lien vdi q u i trinh hinh cic dun cat ngim (hay sdng cat) va chuyen van td td theo ddng nudc Khi dung miy hdi i m sau dpc sPng, chung ta cd Ihl phat hien hang loat sdng cat cd mat dudi day sdng Ngupc lai, chuyen dpng trang thai la lung, ddng bun cat chuyen ddng nhanh vdi khd'i lupng Idn, dpi dat tdi nong bao hoa ddng nudc Cac q u i trinh bdt pha va chuyin dpng bun cat gay hien tupng xdibdi va phat triln Idng sdng 111 Qua trinh phat triln Idng sdng Iudn gin liln vdi hai hien tupng xdi sau va xdi ngang Cac hd xdi sau thudng khd phat hien, chung ta phai khao sat bing cac thiet bj sau Ngupc lai hien tupng xdi ngang de dang nhan biet qua khao sit va phan tfch cac bdc anh hang khPng Hien tupng xdi ngang hay gin liln vdi qua trinh long din udn khuc, tao bai bdi phfa bd ddi dien Xdi ngang khdng chi xay dieu kien Iii ldn, ma cdn xiy manh me myc nudc tha'p, td'c dp chiy cao nude tap trung ldng din thiet dien hep va thieu hut ddng sa bdi mua khd Qui trinh xdi ngang manh tao cic vach "him ech" va gay trupt Id phin vat lieu vi cdng trinh phfa tren bd lu vira va Idn hon m/s lu ldn, cpng vdi cac hien tupng nude chiy bl mat tren dja hinh ddi ndi dd'c dl xay hien tupng xdi Id ddi vdi nhung khu vyc cd Idp phu phong hoi ye'u, dp gin kl^t kem Do vay vdi hien trang phan bd trim tfch hien dai tai day, tdc dp cua ddng chay d Idp sit diy sdng dat m/s deu cd the bdt pha cac cap hat cd dudng kfnh nhd ban 0,1 mm Ngoii ra, d day cin luu y den boat dpng cua nudc ngim d ddi trim tfch bd rdi kl chan nui Yeu to nudc ngim cd anh hudng rat ldn tdi kha nang khang xdi trudc tie ddng cua ddng nudc sdng ca vao thdi ky mua khd kiet va mua mua lu Phin tfch ham lupng phin tram cip hat, dudng kfnh trung binh, dp chpn lpc, dudng cong tfch luy va dien phan bd cua chung tai khu vuc ldng din, cho thi'y : trim tfch d day phin ldn thupc loai cap hat nhd (cat nhd, bdt, bpt-set) cho nen chdng rit dl bj xam thye bao xdi mdn, dudng kfnh trung binh cua tram tfch thay ddi nhanh giiiii cac khu vyc, the hien su bien ddng cua trudng ddng chay sdng d day dien phdc tap Ngoai cdn thi'y phd bien loai trim tfch rdi rac hat nhd nim sat ven bd dpc true dudng Hoing Lien - Bach Dang, diiu kien td'c dp ddng chiy cao ca vao thdi ky mua lu va miia kiet da ga.y xdi sau Idng din va xdi ngang vao ddi bd Cdn d nhung doan bd cd trim tfch cit trung - cat nhd nim sat bd thudng xuat hien cac bai tfch tu ven bd, hoac bai ndi giira sdng Song sy tdn tai phat triln cac bai bdi cat nhd, cit trung Idng din sdng thudng dua den sy thay ddi qua trinh va long din, ddi hudng cua ddng chay din tdi sy pha huy gay sut Id d nhung doan sdng khdng cd bai, dudng bd bj 15m nha't d khu vyc cd thinh phin vat chit cau tao la nhung tram tfch bd rdi cd cap hat nhd Cic dac trung So, Sk va dudng cong tfch luy cua trim tfch khu vyc nghien cdu cho thiy ' UC nim mdi trudng cd che dp dpng khu V lyc kha manh bdi phin ldn cac loai tram tfch d diy diu cd dp phan tuyen va mai mdn kha td't (So = 2), dp chpn lpc thudng bi thay ddi theo cap hat trim tfch KET LUAN Xet dudi gdc dp thach dpng lyc, tram tfch ting mat d day thupc vao loai de bj bien ddng : cic trim tfch cap hat nhd de bj xam thuc bao xdi mdn, tram tfch cat trung tdi san sdi thudng tao nen bai bdi, din din thay ddi qua trinh Idng din Khu vyc nghien cdu thupc thung lung sdng miln nui nen td'c dp ddn" chay d day kha Idn, thudng •vupt qua - m/s - Xdi Id bd sdng Hdng xiy manh me, td'c dp xdi Id d phfa bd phai sdng Hdng, khu vyc trudng hpc xa Van Hoa khoang 10 m/nam - Ca'u tao va hinh thai ddi bd, tfnh chat dja chat cdng trinh, nudc dudi da't, bd sdng cao, dp dd'c sudn bd gin thing ddng, cic dirt giy Tan kien tao nam sat bd sdng la nhirng yeu to khdng bin virng dl gay xdi Id bd sdng - Dp ddc dja hinh day song Idn, Idng din hudng thing vao bd, giy xdi Id manh - Td'c dp ddng chiy ca mua kiet va mua Iii diu rit Idn, gay xdi Id lien tuc hai bd sdng Hdng d day, khdng phu thupc theo mua Bai bio la kit qua cua dl tai : "Nghien cun dinh gia dac diem dia dpng lyc hien dai phd Lao Cai vi md'i quan he vdi tai bie'n dia chi't" Trung tam Hd trp Nghien cdn Chau A, Dai hpc Qudc gia Ha Npi tai trp TALLIEUDAN [11 P.G KDCELEP va nnk, 1984 : Sd tay tfnh loan thuy lyc Nha xui't ban Nong nghiep - Ha Npi (dich idNga van), 312tr [2] V.D LOMTADZE, 1978 : Dja chat ddng Iuc edng trinh Nxb Dai hpc va Trung hpc chuyen nghiep [3] NGUYfiN TRONG YEM, NGUYiN DANG TOC, 2000 : Diiu tra danh gia hien tupng trupt - Id nguy hilm va kien nghj cic giai phap phdng tranh giam nhe thiet hai d mpt so vung trpng dilm thupc tinh Lao Cai Bao cao khoa hoc, Lao Cai 363 [41 CPng ty Tu van Tlhe't ke DCCT, 1999 : Bao cao dia chit eong trinh ciu Phd Mdi - Lao Cai t51 Cong ty Tu vin Thiet ke DCCT, 1997 : Bao cio dia chit cdng trtnh dai phat - truyen hinh tinh Lao Cai [6| Tdng cue Md va Dia chat, 1989 : Dia chat Viet Nam Tap 1, Dja ting [71 Tdng cue Khf tupng Thiiy van, 1989 : Tap so lieu khf tupng - thiiy van, tap 1, SUMMARY Study results on the Red River bank erosion in the area of Lao Cai city The paper introduces study results on current erosion state of the Red River banks and erosioncausing factors in the area of Lao Cai city Erosion 364 along the Red River has occurred drastically in recent years, erosion rate is up to 10 m/year nearby a school at Van Hoa commune Geomorphology, geology and hydro-litho dynamics are the main factor causing erosion along the river Studying on factors of geomorphology and geology shows that geometry and structure of river banks including materials, geotechnical setting, groundwater levels, heights and slopes of river banks, as well as active tectonic faults are the most favorable factors for river bank erosion Hydro-litho dynamic factors such as : high angle of river bed, dired channels to river banks are major causes to intensify erosion Flow velocities in both dry and rainy seasons are very high, causing continuous erosion at both sides of the Red River Ngeiy nhdn inu : 21-7-2010 Vien Dia chdt (\^ien Khoa hgc vd Cong nghe Viet Nam) ... bd sdng Hong d phd Lao Cai cho thiy, xdi Id khu vuc Ngdi Xum, nai cd dudng sit Ha Npi - Lao Cai chay qua, cd mat cit bd song thupc.ldeuj va khiLvuc-Xoi Id thein_ song bic khu vyc Phd Mdi, xa Van... Van Hoa, ngdi Xum va cac khu vyc xdi Id cd ca''u tao td da Neogen - De Td d khu vyc Phd Mdi, khu vyc trudng hpc xa Van Hoa [6j - Ddt giy phi''a phai nam sat bd song b cac khu vuc xdi Id cd ciu tao... nhan cpng hudng gay xdi Id bd phai sdng Hdng d khu vuc Yeu td thuy - thach dgng luc a) Bien dong mua va lu tai Lao Cai Lupng mua d khu vuc phd Lao Cai tuang ddi ldn, trung binh 1.800 mm/nam Mua