• KHOA HQC CONG NGHE <
NGHIEN CU'U CH^ TAO VA LAP OAT THU' NGHIEM CAU KIEN TU'QNG B I S N BAO VE' KHU DU LjCH
HON D A U R E S O R T
PGS.TS LE HAI TRUNG Khoa Ky thudt bien - Tru&ng Bgi hgc Thuy lgi
NCS.TANG XUAN THO S& Ndng nghiep va PTTN thdnh phd Hdi Phong, NCS Khoa Ky thuqt Biin - Tru&ng Bgi hgc Thuy lgi
TS. NGUYEN NGOC LINH Khoa Cff khi - Tru&ng Bgi hgc Thuy Iffi
KS. MAI DUY iOiANH
Vien Ky thudt cong trinh - Tru&ng Bgi hgc Thuy lgi Tom tat: Mat bang hgn che vd yeu cdu thdm my cao dang ddt ra nhimg tieu chi ngdy cdng chgt che vd phiec tgp doi v&i cong trinh bdo ve b& a nhimg khu do thi vd khu du lich ven bien. Ben cgnh de hay ke, tuang bien dang tr& nen pho bien trong quy hogch viing ven bien. Bdi bdo ndy nhdm nghien Clin de xudt mpt so dgng mat cdt ngang tu&ng hieu qud trong viec gidm song trdn, song bdn toe thuang gdy nguy hiem cho ngu&i vd ca s& hg tdng sau tu&ng. Tie do, cdc cdu kien tu&ng bien be tong cot thep da duac che tgo vd lap ddt thie nghiem tren mpt tuyen ke dd bdo ve khu du lich Hdn Ddu.
Tir khoa: tu&ng bien, song trdn, sdng bdn toe, thu nghiem
Abstract: It is the limitation in area and landscape requirements that stimulates the development of protection structures in coastal tourism areas and cities. Next to dikes and revetments, seawalls have become more popular in the master plan of any coastal zones. The paper proposes three cross-sections of seawall with bullnose in order to effectively reduce wave overtopping and splashing-up. A number of precast concrete units were produced and assembled to protect a part of Hon Ddu resort in Do San district.
Keywords: seawall, wave overtoppoing, splash-up, pilot project
1. GIOI THIEU CHUNG toan cfta dan cu va co sd ha tang ngay cang Nude ta cd dudng bd bien dai vdi he thdng de dugc quan tam. Ben canh do, mat bang han che biin da duge hinh thanh tu rat sdm, diu tien la d va yeu cau tham my cao dang dat ra nhung tieu mien Bac. Cac de bien va de eua sdng dugc xay chi mdi chat che va phue tap ban ddi vdi cac dung, bdi tnic va phat trien theo thdi gian va do cdng trinh bao ve bd bien. Chinh vi vay, tudng rit nhieu the he ngudi Viet Nam thyc hien. May bien la mdt giai phap thudng dugc lya chgn chue nam gan day, chiing ta cung da xay dyng trong qui hoach cac khu dan cu va khu du lieh.
thera nhiiu dang edng trinh bao ve bd nhu ke Diin hinh la quan D6 Son - Hai Phdng, biin, tudng bien, de chin sdng, dap rad ban... tudng biin da dugc xay dyng tft nhiiu nara qua Sy phat triin kinh t i - xa hdi khien cho dan vdi hmh thue va k i t elu tuong ddi don gian.
s6 tap trung hinh thanh nen nhieu khu dd thi va Ngay phia sau tudng la via he, dudng giao khu du lieh ven bien. Yeu cau dam bao sy an thong va nha eua. Trong diiu kien triiu cuang
TAP C H f T A l NGUYEN NU(3C 5(5 1-2020 29
• KHOA HOC CONG NGHE • hay ed bao, muc nude dang cao, tuang tac giua
sdng va tudng dien ra rat manh liet (Hmh 1).
Nude tran va ban tde vdi lugng Idn se gay nguy hiem eho dan cu, phuong tien giao thdng va cac cdng trinh xay dyng phia sau tudng.
Hinh 1. Tu&ng bien Do San, Hdi Phong.
Tudng bien vdi mui hat sdng la mot giai phap hieu qua nham giam lugng sdng tran, sdng ban tde gay nguy hi^m ddi vdi ngudi va khu vue sau tudng. Do vay, bai bao nghien cftu de xuat ba dang eSu kien tudng bien vdi mui hat sdng v^
trinh bay viee ehe tao, lip dat thft nghiera tai mdt doan bd bien khu du lich Dd San.
2. NGHIEN CirU DE XUAT MAT CAT NGANG TU'dNG BIEN
Vi tri tirdng bien
Vi tri eua tudng bien tren bai anh hudng tdi sy tuong tae giua cdng trmh va cae qua trinh ven bd nhu sdng va hien tugng xdi Id. Cdng trinh dugc bd tri d phan eao eua bai se khdng thudng xuyen tuong tae vdi sdng va qua trinh van chuyen bun cat. Ngugc lai, cdng trinh d khu vyc cd bien ddng hang ngay ve muc nude se anh hudng qua lai lien tue vdi cac qua trinh thuy dgng lyc va van chuyen bun eat.
Tudng bien cd the dugc phan loai theo Weggel (1988), phu thudc vao vi tri eua tudng tren bai bien (Hinh 2). Tiep giap gifta tudng va mat cat bai bien cd the thay ddi theo thdi gian khi cao dp bai va vi tri dudng bd thay ddi, dac
biet trong thdi gian dai va khi mye nude bien dang eao. Vi tri cua tudng tren bai ehi phdi viec lua chpn hinh dang va kich thude tudng ciing nhu ket eau vat heu.
Hinh 2. Phdn logi vi tri tuang bien (Weggel 1988).
Vi tri dy kiin cftng vdi dang mat cat ngang sg dugc lya chgn va xem xet thera cac yeu td nhu dang ket cau, edng nghe thi edng, vat lieu xay dung.Vi tri tudng cang tien vd phia biSn thi kieh thude cdng trinh cang tang len va bi|n phap thi edng se phftc tap ban. Trong trirdng hgp lan bien thi dien tieh mat bang dugc md rdng ti le thuan vdi viSe tuy§n cdng trinh dich ra xa bd.
Bang 1 di xuat mdt sd dang mat cit ngang (MCN) tudng bien khac nhau phan theo vi tri tren bai biSn.
Bang 1. Mat cat ngang tirdng theo vi tri Chieu
cao tudng Cao: >
3~4m Trung binh;
2~3m Thip: <
2m
MCNdi xuat Mat dung,
nghieng, bac thang Mat bae thang, mat
eong Mat cong,
nghieng, dung
Vitri
Tryc tiep tren bai/
be thap Tren b§
Tren be Phan
lo^i theo Weggel
1,4,5
1,2,3
1,2,3,6
30 TAP CHl TAI NGUYEN Nl/OC S6 1 -2020
Chung tdi de xuit ba dang tudng dua tren kich thudc tuong ddi bao gdm tudng eao, tudng trung binh va tudng thip. Tuong ftng vdi chieu eao la dang mat elt ngang ed the ap dyng.
Tudng eao dat tryc tiep tren bai ho^e be thip thich hgp vdi dang mat diing, nghieng hay bac thang. Tudng cao trung binh tr^n be cd thi ap dung dimg mat b^c thang, mat cong. Tudng thip tren be nen ed dang mat eong, mat nghieng. Ben canh do, tudng bien dang mat dung diu cd thi ap dyng eho tudng vdi hiu hit chiiu cao, so dd bd tri do sy dan gian trong eau tao, thi edng va duy tu, sua ehfta.
De xuat mdt so d^ng mat cat ngang Trong mdt sd trudng hgp, edng trinh bao ve bd da duge xay dung va cin duge nang elp hay thay the. Phuang an ed thi can nhic la lip dat eSu kien tudng bien trSn be bing da/ be tdng hay mpt phan than cua ket elu ciu hi6n ed. Dae diem cua tudng bien dang nay nhu sau
- chieu eao khiem tdn < 2 m di thuSn lgi cho viee ehe tao, van chuyin va lip dat;
- nen duge che tao theo dang khdi hop vdi kieh thudc ba chiiu can ddi;
- mat cat ngang hmh dang tft dan gian tdi phftc tap nhu nghieng, gay khuc, cong ngugc;
- cd miii hat sdng nham han che sdng tran va sdng bin tde;
- nen bd tri d nai cd su chenh lech vi cao dp dang ke giua bai trudc va khu vue phia sau tudng;
- dugc bd tri sat bd, tren mye nude trieu cao;
- cd the bd tri dinh tudng la ldi di bg.
Theo dd, ba dang MCN tudng bien vdi mat nghieng, mat diing va mat eong duge de xuat nhu Hinh 3.
3. THIET KE TU^OfNG BIEN KDL HON DAU, DO SON
Khu du lich Hdn DIU cd dien tich 120 hectare nam d cye Nam cua ban dao Dd Son.
Khu ldi gdm cac cdng trinh kien cd nhu khach san, nha hang, nha hat... dugc bao quanh bdi tuyen ke thu nhat. Phin md rdng nam ngoai khu loi va duge bao ve bdi tuyen ke da thft hai (Hinh 4). Doan tudng biin thu nghiSm dugc bd tri tren cung tuyin vdi Idp ke thft hai de khdng pha vd canh quan kiin tnic tdng the; eao trinh dinh tudng dugc lya chgn khdng thap hon dinh ke hi6n tai la +6,35 m (Hinh 5).
Mat Nghieng Mat diing Mat eong Hinh 3. Mat cdt ngang tu&ng bien co miii hdt song dgng mat nghieng, mgt dimg vd mgt cong
Hinh 4. Vi tri hai tuyin ke bdo ve KDL Hon Ddu; dogn tuang bien thu nghiem dupe
bo tri tren ciing tuyen phia ngodi Mat elt ngang tudng biin thft nghiem da duge di xuit d phin trude (Hinh 3). Kieh thudc hinh hpc dugc xae dinh dua tren nang lye che tao van khudn, thi cdng due va lip dat elu kien. Theo dd, chiiu cao elu kien la 1,5 m;
chiiu dai 1,2 m; chiiu rdng dinh 0,96 m; chiiu rdng day 1,2 m.
TAP CHfTAl NGUYEN Ni;(3CS6 1-2020 31
• KHOA HOC CONG NGHE •
Mill c i i D ^ Dl&^ Kf DA c u 4600 400 400Q , ^500
115 T /|-^"5 \ / IIWNG OEH Trt) NCHlEU
/fiK^ 5. /fie« frawg A:e dii vd vi tri die kien Idp dgt khoi tu&ng bien.
Bieu ki§n biln
Doan tudng thft nghiem nam trong tuyen edng trinh bao vS khu do thi, khu du lich phat trien. Do dd, ta cd the lua chgn cdng trinh cap II hoac III, tuong ftng vdi tan suat thiet ke 1 hoac 2 % [TCVN 9901: 2014]. Myc nude thiit ke (MNTK) cd thanh phan bao gdm thuy trieu thien van Idn nhat va nude dang ftng vdi tin suat thiet ke. Dudng tan suat mye nude tdng hgp tai diem MClO Bang La, quan Dd Son, Hai Phdng cho ra MNTK = + 4,0 m ung vdi TCAT ^ 100 nam hay tan suat thiet ke Ptk = 1%; +3,1 m 3,33%; va + 2,73 m - 5%
[TCVN 9901: 2014].
Chieu eao sdng nude sau phyc vu tinh toan truyen sdng dugc xac dinh dya vao sd lieu sdng nude sau thye do qua nhiiu nam tai tram Bach Long Vy (Hinh 6). Vdi tin suit thiit ki P = 1%
dya vao dudng tan suit WeibuU tra dugc chieu eao sdng tai vung nude sau Ho = 8,2 ra. Chu ki sdng dac trung d nude sau tinh theo quan he de xuit cua SPM 1984.
Dia hmh day biSn khu vyc dy an dugc do ve vdi ti le 1/200 de phye vy thiet ke. Vdi hudng tuyin doan tudng thu nghiem, hudng sdng Ddng Bae duge danh gia la gay bat lgi cho cdng trmh (Hmh 4). Sft dung Wadibe (Tuin 2015), ta tinh truyen sdng tft vftng nude sau vdi eac tan suat P ^ I; 3,33 va 5% ve phia tuyen cdng trinh thft nghiem. Vi du, Hinh 7 minh hga ket qua tinh toan dien bien chieu eao sdng ngang bd vdi tin suit thiit ki P - 1%
PhSn b i c h l b cao sdng ngang M
Is: 4 i:
:^
1 |+::j:..:
-•
I::;;::::
- f - i - ' • ::::[::::;::•
dliSS:;;
iiiS:;!;;:;
- • • - •
;;;;|i
- • • • -
;:;;!;
Hinh 6. Du&ng tdn sudt song cue tri tgi trgm Bgch Long Vy.
Khoang cia\ vi plila biin Xb (m)
Hinh 7. Dien bien chieu cao song ngang b&, tinh todn v&i Wadibe, P = 1% (net liin do:
dia hinh ddy bien, net cham: Hrms vd net diet:
muc nuac tinh).
Kiem tra liru lirgng sdng tran
Thdng thudng ehieu eao luu khdng cua dinh cdng trinh Re dugc xac dinh theo tieu chuan sdng tran vdi luu lugng eho phep phu thudc dp ben eua ban than cdng trinh va dam bao cae dieu kien van hanh khac. Luu y ring cao trinh dinh tudng thu nghiera duge lya chgn trudc, tuong duong dinh ke hien huu. Do dd, ta sft 32 TAP CHf TAI NGUYEN Nl/(3C S6 1 -2020
dung s6 tay song tran EurOtOp 2018 (16 kiSm tra Imi lugng tuong ung voi MCN (Hinh 3) va cao trinh dinh tucmg dir kign Zd = +6,35m.
Cao trinh dinh tu6ng dugc xac dinh nhu sau
Zj=MNTK+R^+a (1) voi Re la chieu cao liru khong tinh ttr MNTK
va a la tri so gia tang do cao an toan phu thupc c i p cang trinh [TCVN 9901: 2014]
Liru luong song tran don vi qua tucmg b i l n dugc xac dinh theo cong thuc vgi song khong vg nhu sau:
^ 0 , 2 e x p - 2 , 3 R^
~H~.
1 (2) trong do:
q luu luong tran don vi [m^/s/m];
Hmo ehieu eao sdng thiet ke = Hj tai chan cdng trinh;
g gia tdc trpng trudng ^ 9,81 [ra/s^];
Yp he sd chiet giam sdng tran do anh hudng cua gdc sdng tdi xien gdc
;'^ = I - 0 , 0 0 6 3 | ; 5 |
YT he sd chiet giam do dp nham cua raai khdi phu mai.
Cdng thftc (1) va (2) dugc su dung d i tinh sdng tran va cao trinh dinh tudng bien. Bang 2 trinh bay ket qua tinh Z^ theo cae mftc luu lugng q vdi tan suat thiet ke P ^ 1; 3,33 va 5 %.
Bang 2.1. Cao tiinh dinh tirdng Zd tinmg img vdi liru lirgng song tr^n q P[%]
1 3.33
5
q [m^/s tren m]
0.005 11.21 9.16 8.24
0.01 10.48 8.52 7.63
0.02 9.75 7.88 7.03
0.03 9.33 7.50 6.68
0.05 8.79 7.02 6.24 Vdi cao trinh dinh tudng dy kien +6,35 m, luu lugng sdng tran udc lugng la trong khoang 0,03 ~ 0,05 [m^/s tren m]. Nhu vay, cao trinh dinh tudng va ke dam bao khdng gay bat lgi hay
nguy hiem cho c a sd ha tang va he thdng tieu thoat nude hien tai. Kich thude tudng bien de xuat se dugc dua vao ehe tao van khudn va diic eau kien thft nghiem.
4. CHE TAO VA LAP D ^ T THU" NGHIEM Van khuon cho cau kien diic san Cau kien be tdng due san rat phft hgp de su dung trong edng trinh bi§n. Viee lap ghep eac cau kien be tdng, be tdng cdt thep due san cho phep nit ngan thdi gian thi cdng, giam nhan cdng lao dgng va thdi gian chet do ehd dgi anh hudng cua thdi tiet xau. Han nfta nhieu khoan chi phi cd the tiet kiera duge.
Cau kien be tdng due san thudng dugc lam t u be tdng ket eau thdng thudng hoac be tdng du ung lyc, dugc thiet ke vdi eudng do du b i n trong sudt qua trinh xay dung nhu che tao, van chuyen, lap dyng va qua trinh lara viee sau khi ket cau da hoan thanh. Kich thudc va trgng lugng eua eae eau kien due san eung nhu dja diem che tao dugc quyit dinh bdi kha nang thi edng eu the, nhu edng suat cua cac thiit bi thdng thudng va thiet bi ndi d i van chuyin l i p dat. Cd hai dia diera che tao e l u kien due s i n thudng dugc lua chpn la nha may san xuit e l u kien be tdng va hien trudng. Tuong ung vdi cac dia diem dd la edng nghe due, dac trung bdi loai khudn due be tdng, duge lya ehgn sft dung.
Hinh 9. Vdn khuon dinh hinh phuc VIA due cdu kien tu&ng bien thu nghiem
TAP CHf TAI NGUYEN Nl/OC SO 1 -2020 33
• KHOA HQC CONG NGHE • Ddi vdi cac loai cau kien due san cd mat cat
phuc tap nhu eua tudng bien de xuat thi khudn due dinh hinh bang thep la giai phap phu hgp (Hinh 9). Yeu cau ky thuat ddi vdi khudn diic cho cac cau kifn cua tudng bien thft nghiem dugc xay dung dua tren cae tieu chuSn cd lien quan d trong va ngoai nude, cy the la cac yeu eau ehung ddi vdi khudn due, vat lieu lam khudn due, cae cdng tae che tao, lap va thao khudn due. Khdng mat di tmh tdng quat, cac yeu eau ky thuSt ddi vdi khudn due eua tudng bien thft nghiem neu tren ed the ap dyng cho cac loai mat cat tudng bien khac.
Cdng tac dAe v^ dirdug hd cau ki@n Sau khi cd bp van khudn mau, cdt thep dugc tinh toan bd tri eho ba dang MCN thft nghiem (Huih 10). Vdi dae thft ve hinh hge, cac cSu kien thu nghiem dugc diic be tdng d tu the nam. Mgt mat ben phang cua van khuon dugc ke tren mat nam ngang va be tdng dugc do vao tu mat phing ddi dien phia tren (Hinh 11).
be tdng dugc kiim tra trudc khi xuat xudng.
Tiep dd, eau kien tudng bien duge van chuyen tdi nai lap dat.
Hinh 10. Cong tdc lap dimg cot thep vd vdn khuon
Sau qua trinh dudng hd tiSu chuin, van khudn duge thao dd (Hinh 12). Do duge due nam nen viec thao dd dugc thuan lgi dl dang, van khudn gift duge nguyen hinh dang, kich thudc. Cac kieh thudc eo ban cua cau kien duge do dac, ddi chieu vdi ban ve thiit ki. Cudng do
Hinh II. Cong tdc do be tong vdo vdn khuon vd ddm
Hinh 12. Cong tdc thdo da vdn khuon
Lap dalt ciu kiin tirdng biln
De lap dat nhftng eau kien tudng biin diie san, mat bang va h& mdng cin duge ehuin bi.
Mat bang can du rpng de bd tri vat heu, may thi edng va de dang thuan lgi cho xe v^n chuyin, xe elu tiep can. Be mdng BTCT duge bd tri trSn nin da hge, chinh la mdt phin than ke da hien hftu, dS dugc lu len dung yeu cau thiet ke (Hinh 13).
Sau khi be mdng du eudng do, lan lugt cac eau kien due san dugc lap dat. Dinh cSu kien duge bd tri sin hai khuyen thep dB mde cap elu va dam bao can bang, dn dinh khi di chuyin, lip
34 TAP CHf T A I NGUYEN N U O C SC5 1 -2020
dat (Hinh 14). Tftng elu kien duge eau va dat vao vi tri da dinh sin tren bS mdng b6 tdng.
Hinh 13. Cong tdc chudn bi mat bdng, be mong tu&ng bien thie nghiem
Hinh 14. Cdu lap cdu kien tuang bien thie nghiem tgi hien tru&ng
di dam bao tuyen edng trinh tuan theo thiet ke.
Dinh va lung cac elu ki£n dugc dd giang be tdng de tang su dn dinh va tham my. Sau khi lip dat hoan ehinh, doan tudng thft nghiem vdi tdng chieu dai 32 m (Hinh 15) duge theo doi ehuyen vi, liin va kiem tra cudng dp be tdng theo dinh ki.
5. KET LUAN
Mpt doan tudng bi§n da duge thiet ke, ehe tao va lip dat thu nghiem d Khu du lich Hdn Dau, quan Dd Son, thanh phd Hai Phdng. Ba dang m^t cat ngang dugc nghien cuu de xuat nham giam thieu sdng tran va sdng ban tde qua tudng, tang sy an toan cho eo sd ha tang va con ngudi phia sau tudng. Ba bd van khudn dinh hinh dugc thiet ke va sau dd duge ehe tao tai nha may. Mdt loat cau kien tudng bi6n BTCT dugc due va dudng hd theo qui trmh ti^u chuan tai eo sd san xuat be tdng chuyen nghiep. Khi dam bao eudng do, toan bd eau kien cua 3 dang tudng mai nghieng, mat dftng va mat cong dugc van chuyen va lap dat ISn be chuan bi sin. Hien tai, doan tudng thft nghiem dai 32 m dang dugc theo ddi, quan trae phuc vy eac ndi dung nghien ciru ti6p theo. Doan tudng raang tinh tham my, hai hda vdi eanh quan mdi trudng khu Hdn DIU
TAI LIEU THAM KHAO
Hinh 15. Cdng trinh tu&ng bien thu nghiem duac lap ddt tren tuyen ke dd hien hiru
[1] EurOtop 2018. Sd tay sdng tran chau Au [2] SPM 1984. Shore Protection Manual.
[3]TCVN 9901:2014. Yai d u thiit kide biia [4]Tuln, T. Q. Hudng din su dung Wadibe 2015.
[5] Weggel, J. R 1988. Seawall: The need for research, dimensional considerations and a suggested classification in the effects of seawall on the beach. N. C. Kraus and O. H,. Pilkey (Volume Editiors), Journal of Coastal Research, SI 4: 29-40.
Lan lugt tung cau kien dugc lap dat ndi tiip
nhau vdi khe hd 1 ~ 2 era Khi du sd lugng yeu Nguai phdn bien: PGS.TS. Dao Van Himg elu, mgt vai elu kien ed the dugc can chinh lai ^"^" ^'?« xong: 12/2019
TAP CHf TAI NGUYEN Nl/(3C S6 1 -2020 35