MOT S6 NGHIEN CCaj ONG DUNG
C O N G T R I N H BI^NTRONG LL/C 0^ GIA C6 VA
XAYDL/NG
M 6 | CAC C O N G T R I N H BI^NdvONGDKIVATRL/CJNGSA
PGS.TS Oinh Quang Cudng Vidn Xay dung Cdng trinh biin Trudng Dai hge XSy dt/ng
Tdm tit: BSI bao tdm tit mpt sd kit qua nghien eUu vi tinh toan tac ddng eda mdl trudng biin ten kit eau cdng trinh biin trgng lue bd tdng, phuang phap tinh toan kit eau, nin mdng cdng trinh biin trgng lue bd tdng va nhifng Ung dung thue ti tai Viet Nam. Thdng qua vide mt kinh nghiem tU nhifng Ung dung thue ti, dSt van di nghidn eUu tiip theo nhim img dung rpng rai cae edng trinh bing be tdng di dd ddn biin tai eae dao d Trudng Sa va vung DKI.
Summary: This paper summarizes some problems about caleulating diffraction wave loading on gravity concrete structures; some other problems about finite element method to analysing the gravity concrete structures, gravity concrete foundation and their application to Vietnam condition are presented. To learn from experience of application of the gravity concrete principle In Vietnam condition, this paper sets up some eminent problems to be solved for continued for more common applieation to the gravity concrete platform of light tower on Tmong Sa and DKI area.
1. MO DAU
Cdng trinh bien trpng lUc la loai cdng trinh theo nguyen ly mdng ndng, ddng dn djnh tren mat day bien nhd trpng lupng ban than va trpng lupng cdng nghe. Mpt trong nhiJng uu diim ndi bat cda cdng trinh bien trpng lUc la toan bd (hoac phin Idn) k i t c i u cdng trinh dupe c h i tao d ven bd, sau dd lai d i t edng trinh ra vj tri xay dyng danh chim, giam thiiu thdi gian thi cdng ngodi khoi do vay tranh dupc nhdng rui ro khi thi cdng dai ngay d ngoai khoi. De tan dung dupe uu diim trdn day, cac cdng trinh phai dupc thiit k i sao cho tu ndi dn djnh trong qua trinh lai dit td vj tri thi cdng ven bd d i n noi xdy dyng cdng trinh. O i tdng dn djnh cho cdng trinh, thudng c i u tao phin d i Idn d i ha thip trpng tam cdng trinh. Trpng tam cang thip thi cdng trinh cang dn djnh.
Dudi ddy liet ke mdt sd k i t qua nghien cdu nhim irng dung nguyen ly trpng lUc d i gia cd vd xSy dyng eae edng trinh biin d Viet Nam vd de xuit mdi cac v i n de nghien cdu tiep theo nhim dng dung rdng lapi cdng trinh trpng luc be tong d i xay dyng cac cdng trinh d Trudng Sa vd DKI.
2. TiNH TOAN LI/A CHON KET CAU KHOI CHAN DE HOP LY
Mdt trong nhiJng v i n de ein quan tam d i u tien khi xay dyng cac cdng trinh biin trpng lyc bd tdng Id lya chpn hinh dang kich thudc hpp ly eho khdi chdn d i cac edng trinh bien trpng luc,
TAP CHf KHOA HOC CONG NGHe XAY DUNG sdOf-9/2007 93
sao cho cdng trinh phai kha thi v i mat thi edng trong mdt diiu kien ha t i n g cu the, vda dam bao dn dmh ndi trong trang thai thi cdng, lai dat td ven bien ra vi tri xay dyng va vda dam bao diiu kien b i n , diiu kien dn djnh trong trang thai khai thae. Hai dieu kien neu tren day trong nhiiu trudng hpp ed mau thuin vdi nhau. Trong [6] da trinh biy eo sd khoa hpe d i tinh toan lua chpn cac phuong an khdi chan d i cho cac cdng trinh loai nhd phu hpp diiu kien Viet Nam, trong dd mdt trong nhung v i n d i d i mac sai sdt la vide tinh toan chiiu chim cda khdi chan d i cd cau tao chan khay trong cac trang thai thi cdng. Cdng thdc dudi day [6] cho phdp tinh ehiiu ehim cda edng trinh cd ehan khay khi keo ndi tren bien (hinh lb).
S/n
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Trong dd: T: ehiiu chim eda mdng tinh tU mui ehSn khay; P: tong trgng lugng vat thi nil;
Q^^i,: trgng lugng phin ehan khay; y„:trgng lugng ridng eOa nude biin; S:didn tich dSy eiia vat thi nil cd dang tru di/ng (hinh lb); h^f,,,: ehiiu eao kit cau chan khay.
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3. TI'NH TOAN KET CAU KHOI CHAN DE CONG TRINH BIEN TRONG LI/C BE TONG Vide tinh toan k i t eiu khdi ehan de cdng trinh biin trpng luc be tong bao gdm cae van d i : Tinh toan xae dinh tai trpng mdi trudng len khdi ehan d i , trong dd quan trpng nhit Id xac djnh tai trpng sdng, thudng la tai trpng sdng nhieu xa bdi vi khdi d i eda eae cdng trinh biin trpng lue thudng ed kich thudc kha Idn so vdi bude sdng d i dam bao dieu kien ndi dn dinh khi thi congetreen bien va dam bao dieu kien dn dinh khi khai thac.
Trong [2],[3],[4] da trinh bay phUPng phap phan td hdu han de tinh kit c i u cdng trinh bien trpng lye be tdng va mdi trudng sdng bien nhu mdt he thdng bao gdm cae phan td kit ciu la vat ran biin dang va sdng bien la nhiimg phin td nude hdU han va cac phin td nudc vd han, su tuong tac gida mdi trudng nUdc biin va vat ran bie'n dang dupe md ta thdng qua cae phin td tiip xde. Phuong trinh dpng lyc hpc eda he thdng viet dudi dang ma tran cda phuong phap phan tdhOru han nhUsau:
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94 TAP CHI KHOA HOC CONG NGHE XAY DUNG SOOf-9/2007
Dang rut gpn cua phuong trinh (2):
MX + CX + KX = R^ (3) PhUPng trinh ddng lyc hpc (2) la su k i t hpp giiira phuong trinh ddng lyc hpe cua kit ca'u
cdng trinh la vat ran bien dang va phuong trinh dpng luc hpe cda chat Idng - sdng bien - cho phep xac djnh dupe ham t h i van tdc cua sdng bien va chuyen vi cda kit eau. Cac phin td tie'p xdc dupc dai dien bing cac ma tran he sd Cpg, Kps da dupc trinh biy chi tiet trong [5].
Bai toan k i t c i u be tdng cdt thdp irng suit trudc cho k i t cau try dd cdng trinh biin trpng lyc be tdng cung e i n phai xem xet. Cac try dd cua cdng trinh biin trpng luc be tong thudng c6 tiit dien vdnh khuyen. H i u het eae try dd deu phai dat edt thep dng suit trude vdi muc dich khdng che khdng xuit hien vit ndt trong kit c i u try dd. Khac vdi cae k i t c i u xay dung thdng thudng, cae try dd cua cdng trinh bien trpng luc chju tai trpng sdng, thay ddi ehiiu tac dpng theo mua, mat khac vdi cac tiet dien vanh khuyen, thep irng suit trudc dat theo chu vi. img suit trudc cd tac dung triet tieu dng suit keo trong vung chiu keo cda tiit dien tuy nhien lai lam gia tang img suit nen trong vung nen lam eho vung nen lam viec kha nSng n i . De xae dinh chinh xac img suit keo va img suit nen trong tiit dien ed k i d i n cac hao tdn img suit theo diiu kien thi cdng eda Viet Nam cd the ddng cae eong thdc sau [1]:
M.a N OsAs+o^As ^ M.a N AsJcTs+a^)^^
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al=——-- ^ ^ 2^-i ^ = 0,5a, (6)
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Trong dd: M: md men ngoai luc tac dung tai tiet dien; N: luc dge tSe dung tai tiit didn; ug: Ung suit trudc; As: ting didn tich thep img suit trude; a ^: ting img suit hao (of, = 0-^, -1- cr^j -)•' •^M' Ffttf.' md men quan tinh va didn tieh tiit dien da trU nhi/ng vj tri giam yiu do dng ghen chUa thep itng suit trude chiim chd; (erg -^-o^): img suit keo khi thi edng; cr^ la img suit nen Idn thep thudng dSt tai vung nen di tSng kha nSng ehju nen cho tiit didn bd tdng; FJ IS ting dien tich thep thudng bd tri diu theo ehu vi tiit didn vanh khuyen hoac bo tri a vung nen eOa tiit dien ehCf nhat di tSng eudng kha nSng chju ndn cho tiit dien bd tdng; a^ IS cudng dp chju nen tdl ban eua be tdng. Giai phUPng trinh (4) tim dupe Ag; giii phuong trinh (6) tim dupe a'^F'^ lit dd cd the tim dupc F„ bing each chpn a^ theo quy pham.
Ngoai cac v i n d i v i xae djnh tai trpng va tinh toan k i t cau be tdng cdt thep img suit trudc. v i n d i tinh toan nen mdng cdng trinh trpng lyc be tdng da dupe trinh bay ky trong [7].
Nhu vay v i ly thuyet. bdi toan b i n cda cdng trinh biin trpng luc be tong da dUpc giai quyit cd ke d i n diiu kidn thi cdng cda Viet Nam.
TAP CHf KHOA HOC CONG NGHE XAY DUNG SOOf-9/2007 95 N
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4. MOT SO LTNG DIJNG THl/C TE PHUC VU GIA CO CAC CONG TRINH DKI VA THI#T KE XAY DUNG CONG TRINH DEN BIEN VUNG QUAN DAO TRUdNG SA
Ung dung d i u tien ed t h i k i den Id vide dung nguyen ly trpng lyc de gia cd cac cdng trinh biin thep mdng cpc tren n i n san hd. Cac cdng trinh mdng cpc tren nen san hd h i u hit bj su cd - do hoac mng lac Idn [9]. Tae gia bai viit nay cdng vdi tap the cdn bp vidn Xdy dimg Cdng trinh bien da dng dung thanh cdng nguyen ly trpng lyc de gia cd g i n 20 cdng trinh DKI.
Cac phuong an gia cd dupe nghien edu nhU hinh 2, trong dd cac phuang an hinh 2a va 2c da dupe ap dung nhung chi cd phUPng an 2c phat huy dupe hieu qua. Lfu nhupc diim, nguyen nhan thanh edng va thit bai cda cae giai phap gia cd da dupe phan tieh ky trong [9].
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Hmh 3. Cong Ir'mh trong lUc da den bien a ven dao Nam 'Yet a) Phoi canh nhin tif ngoai bien; b) Mat cSt ngang cong trinh
Gin day, trong chiin lupc phat triin kinh t i bien, ein thiet phai xay dyng cac ddn biin d khu vye Trudng Sa. Tac gia bai bao nay dupe giao nhiem vu chd nhiem dy an xdy dung. Vide lua chpn kit cau dd cac den bien bing be tdng edt thep dap dng dupc eae yeu cau ky thuat va phat huy Uu diem v i tinh b i n vdng cda kit c i u trong mdi trUdng bien xam thyc manh d Trudng Sa. Cac den bien cap 2 dupc xay dung d ven cac dao Trudng Sa do khdng cdn dien tich dit dd d i xay dung den bien tren dao. Du an xay dyng cac den biin d ven dao Trudng Sa Idn, ven dao Sinh Tdn, ven dao Nam Y i t va ven dao Son Ca da dupe phe duyet, dang trong qua trinh chuyin giao cho don vj tu v i n lam thiit k i chi tiit de xay dung vao nam 2008. Cae cdng trinh da den bien dupc xay dung ed dang nhu hinh 3. Ro rang, su xuit hidn cda edng trinh da lam thay ddi trudng tac ddng cda sdng bien va ddng ehay ven dao. T i t ca cac van d i ky thuat ap dung de xay dyng eae den bien hien nay d i u dua tren co sd quy pham hidn h^nh v i tinh toan
96
TAP CHf KHOA HOC CONG NGHE XAY DUNG SO Of-9/2007thiet k i cac k i t c i u bd tdng cdt thep cho cdng trinh thuy cdng vd xac dinh cae thong sd sdng theo 14TCN130-2002, mpt trong cae bieu dd de tra ciru tinh chiiu cao sdng vd trude eong trinh dupe dua r a d hmh 4 [10].
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Hinh 4. Quan be giOa chiiu eao sdng vd vS dp sau nude trudc cdng trinh
5. DE XUAT MOT SO VAN DE CAN TIEP TUC NGHIEN CLfU GIAI QUYET
V i mat ly thuyit, cac cdng bd [1],[2],[3],[4],[5],[6],[7],[8] da chdng td kha nang cd t h i lam chd cae thiit k i va xay dyng eae edng trinh biin bing be tdng d ngoai khoi. Tuy nhien, nhu da nhan xet d mue 2 eda bdi viit nay, co sd ha ting va kha nang cda cac thiit bj ky thuat la mpt trd ngai Idn trong vide phat triin xay dyng cac cdng trinh biin trpng lyc be tdng. Nhtimg img dung nguyen ly trpng lUc 6e gia cd cac cdng trinh DKI bing thep bj rung lac tren n i n san hd da dat hidu qua rd rdng, cac cdng trinh sau khi dupe gia ed kha dn djnh trong eae mua bao Idn nhumg nam qua.
Se khdng cd mpt van d i nao c i n bdn luan n i u chip nhan thiet ke va xay dung hang loat cac cdng trinh den bien theo eo sd quy pham hien hdnh.
Tuy nhien, trong qua trinh nghien ciru xay dung du an, da bdc Id nhOmg v i n d i ky thuat ma n i u dupe tiip tuc giai quyet thi cd t h i cd t h i se dem lai nhtmg hieu qua ldn ve ky thuat va kinh t i trong vide lam chd Trudng Sa.
Van de thU 1: Su tuong thieh eda biiu dd cho tren hinh 4 vdi dia hinh cu t h i d Trudng Sa. Thuc t i eho thay, cac dao d TrUdng Sa cd thim nong rdng td khoang vai chuc met den vdi tram met sau dd Id sudn dde ed noi gan nhu dde thing dimg den dp sau 40m, 50m va sau hpn nCra. Ca khu vyc cd t h i md ta nhu mdt he thdng ndi san hd ngim xen lan eae thung lung dudi day bien. Nhu vay dja hinh thuc t i d Trudng Sa khdng phd hpp vdi viec ddng bang tra eho tren hinh 4 vdi gia thiit day bien kha d i u dan va ed dd dd'c td 0,00 d i n 0,10 [10]. Ro rang, niu khdng cd mdt nghidn ciru eu t h i thi v i n de xac dinh chinh xae chiiu cao sdng v8 trUdc edng trinh cung Id mdt v i n d i quan trpng trong thiit k i . Da cd nhtJng nghien edu eho kit qua ban d i u bing vide ddng md hinh STWAVE, day la md hinh cd the dp dung tdt cho cac dja hinh cd cac dao che chin, tuy nhidn v i v i n de dp ddc cua nin thi STWAVE eung chua the giai quyit triet de.
Van de thiir 2: De cd t h i lam chd Trudng Sa. mdi dao deu c i n ed mpt bin cap tau / xudng. N i u khdo k i t hpp trong khi nghien eiru thiit k i cdng trinh thi vdi vj tri dia ly eda cac den biin. vide g i n vdo mdi ddn biin mdt bin cap t i u / xudng Id kha thi. Viee xay dyng mdt edng trinh hdn hop vdi hai chirc nang: dd ddn bien va lam b i n cap tau / xudng se hop ly hon ve quy
TAP CHf KHOA HOC C O N G N G H 6 XAY DUNG SO Of-9/2007
97
md va dau tU so vdi viec xay dung hai edng trinh dpc lap. Bdi vi viec g i n them bin cap tau khong lam tang quy md cda edng trinh dd den biin.
Va'n de thiir 3: Cdng nghe thi eong. Khong the ap dung nguyen cae ky thuat thi cdng cong trinh ven bien d g i n bd d i xay dyng cae cdng trinh ven dao. Bdi vi vide van chuyin mpt khdi lupng vat tU ldn ra dao d i xay dyng rat ton kem va rdi ro vi thdi tiet, giam chit lupng vat lieu (thep, xi mang, nudc ngpt, cat, da,... khi van chuyen tren bien deu rat de bi d nhiem do sdng, gid, mua va viee dd be tdng ngoai dao eung de bj d nhiim do moi trudng khdng khi man). Vi vay khd dam bao chat lupng cdng trinh. Td v i n de thd 3, viec nghien ciru mpt edng nghe c h i tao sin cac kit eiu d trong bd, van ehuyen ea khdi hoac timg eau kien de lap ghep ngoai d i o la can thiit.
Ngoai 3 van de Idn neu tren day, nhimg v i n d i v i dam bao mdi trudng sinh thai, dam bao su tdn tai cda bd dao khi cd eong trinh vi sy xuat hien cda cdng trinh lam thay ddi trudng tac dpng eda sdng va ddng ehay ven dao, van de chdng an mdn eho cdng trinh, v i n d i dao tao can bd theo ddi va cdng nhan tryc tiip thi edng,... cung can thiit dupc nghien cifu phu hpp vdi diiu kidn cu the d cac dao Trudng Sa.
6. KET LUAN
Viec xdy dung hang loat ddn bien d Trudng Sa la mpt dy an Idn trong chiin lupc dan su hoa Trudng Sa va lam ehu biin Ddng. NhOmg v i n d i dat ra d mue 5 eda bai bao ndy ein dupc cac can bd nghien cdu va quan ly xdy dung quan tam. Niu khdng tiip tuc dau tu nghien ciru thi vide xay dyng d Trudng Sa va DKI khd cd t h i dam bao dupe chit lupng, dp dn djnh lau bin va dam bao cae ehi tieu kinh t i cua cac cdng trinh xay dung gdp phin thyc hidn d i an "Chiin lupc biin Viet Nam d i n nam 2020" eda Nghj quyit Trung UOng Dang khoa X.
Tai lieu tham khao
1. Dinh Quang Cudng, 1997. Ban v i tinh toan k i t eiu be tdng edt thep dng suit trudc cho edng trinh biin trpng lyc tiit dien vanh khuyen - Tuyen tap edng trinh khoa hpc Trydng OHXD, sd 2 nam 1997.
2. Dinh Quang Cudng, 1998. Phuong phap phin td hiJu han giai bai toan ddng lUe hpe phi tuyin ap dung cho cdng trinh bien trpng lyc bing be tdng cdt thdp - Tuyin tap Bao eao khoa hpc - Hdi nghj KHCN bien toan qud'c l i n thd IV.
3. Dinh Quang Cudng, 1999. Ap dung phuong phap phin td hiJu han de giai bdi toan ddng lUc hpc tUPng tae gida sdng biin va edng trinh trpng luc be tdng - Tuyen tap edng trinh khoa hpe - Hdi nghi Co hpe vat rin biin dang toan qud'c lan thd sau - HN -1999.
4. Dinh Quang Cudng, 2000. Sd dyng bien ban vd han trong phuong phap phin td hdu han d i giai bai toan dpng lye hpc tuong tae gida sdng bien va cdng trinh trpng luc bd tdng cd k i den biin dang cda kit ca'u cdng trinh - Tap chi Oang kiem Viet Nam sd 4 nam 2000.
5. Dinh Quang Cudng, 2000. Tinh toan dp b i n eua edng trinh bien trpng luc be tdng cdt thdp, luan an tien sT ky thuat, Oai hpc Xay dung nam 2000.
98 TAP CHf KHOA HOC CONG N G H £ X A Y DUNG SOOf-9/2007
6. Dmh Quang Cudng, 2000. Nghien edu lya chpn phUPng an khdi chan de cho cae cdng trinh biin trpng lye bd tdng loai nhd - Tuyen tap cdng trinh khoa hpc Trudng OHXD sd 3 ndm 2000.
7. Dinh Quang Cudng, Bui Thi Anh, Le Van Khoa, 2002. Xac dinh dp lyc de mdng cac cdng trinh biin trong luc be tdng loai nhd - Tuyen tap cdng trinh khoa hpc Trudng OHXD sd 1 ndm 2002.
8. Dinh Quang Cudng, 2006. Tinh toan dp b i n k i t cau try dd va d i m tru dd cda cdng trinh bien trpng lyc be tdng - Tap ehi Khoa hpe cdng nghe bien T6 -(2006), sd 2, trang 90-97.
9. Dinh Quang Cuong, 2005. Estimations of actual state and select the solution for re - design and consolidation some offshore piles-steel platform on the coral and madreporian basis Proceedings of the International workshop Hanoi Geoengineering 2005 "Integrated Geoengineering for a Sustainable Infrastructure Development".
10. 14TCN 130-2002, HUdng dan thiit k i de bien.
TAP CHi KHOA HOC CONG N G H $ X A Y DUNG SOOf-9/2007 99
