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Tap chl GTVT 10/2012 I g
NGHIEN cufu SUfC KHANG CUC ONG THEP TRONG DIEU KIEN DjA CHAT VIET NAM
T S . NGUYEN T H ! T U Y E T TRINH Trudng Dgi hgc Giao thdng vdn tai
T h S . NGO C H A U PHUONG
Trudng Dgi hgc Giao thdng van tai (Ca sd ii, TP. HCM) K S . KOUICHI INOKUCHI, K S . M A S A Y A HIGASHI Tap dodn Thdp Nippon Steel Corporation, Tokyo, Nhgt Ban
T o m t a t : Bai bdo idm rd cdc van de nhU: D0c diem dja chit d Vidt Nam; Cdc tieu chuan thiit ki cgc d Vigt Nam hidn nay cd cdc cdng thtfc tinh todn sUc khing cua cgc khdc nhau do tham khao Tieu chuan thiit ke cgc cua cdc nudc khac nhau trong dd cd Nhgt Ban; Thiit ki sdc khdng cgc dng thep dp dyng Tidu chuin thiit kiNhgt Ban cd kha nang Id thiit ki kinh ti vd hgp ly trong dieu kign dia chit cda Vidt Nam.
Abstract: The Article makes clearly some issues such as: 1) Geological condition of Vietnam; 2) Currently, Vietnamese Specifications have different calculation formulas of pile resistance due to refer to from different foreign countries documents including Japan; 3) Resistance design of steel pipe pile, that applying Japanese Specification have possibility giving economical design and reasonable design in geological condition of Vietnam.
TCr khoa: Ciu tnie dia ting, diiu kien dia chat, khi ning chiu luc, thd tdi, tidu ehuan thiit ke, kit qua thiit ke.
1 . G i d i t h i # u
M d n g cpe dng thep dUde s d d y n g kha phd b[en trdn the gidi { c h i l m tren 30%) nhu d My, chau A u , Han Qud'c, N h i t Bin... 6 Vidt Nam, trUde nam 1975 cpc dng thep dUpc s d d y n g kha phd bien trong cae edng trinh n h u cau Sal G d n , c l u Rgch Chide, c i n g T i n C i n g { T P . H C M ) ; C a u T r i n HUng D g o (Binh Thugn) va cac c l u tren Qudc Id 1; Q u i n e i n g Cam Ranh (Khanh H d a ) ; C i n g chfnh H i i Phdng ( H i i Phdng); Tuy nhidn hidn nay, eoe thep lgi ri't ft dupc s d d y n g cho ket ed'u mdng edng trinh xay d y n g vdi nhdng ly do ehd y l u mang tinh chd quan cua ngudi thiet k l . Hien tai va trong tUdng lai, vdi tdc dp p h i t t r i l n nhanh chdng cda ed s6 hg t i n g nhu ket c l u cau Idn, kd't c a u c i n g nUdc sau va kd't eau can dUa vao khai thac nhanh chdng... dac biet kdt eau xdy d y n g trong khu v y c n i n di't y e u , c d xet den ddng da't, vigc ap d y n g kdt c a u mdng cpc dng thep vdi eae uu d i l m n h u cUdng d d cao, c h a t lupng cao va thdi gian thi c d n g nhanh... se ddi hdi ngay cang tang eao.
Mat khac, kinh nghiem v l thiet ke, thi cdng v i ap d y n g cpc dng thep d Vidt Nam chua n h i l u . Vide ndm d u p c triet d l cac v i n de lidn quan den c d n g nghe CQC d n g thep eung nhu xac djnh k h i nang ap d y n g nd d Vidt Nam la rat can t h i e t
V d i cac nhdn djnh nhU t r d n . T a p d o a n T h e p Nippon Steel Nhdt B i n (NSC) va Nhdm nghidn c d u
Trudng Dgi hgc Giao thong van t i i Viet Nam (UTC) da hpp t i e nghien edu c i c van dd Men quan den cpc dng thep d Viet Nam theo ba bUde: (1) Phan tich, d i n h g i i thuc trang v l cac logi ket cau mdng cpc da va dang s d d y n g , dieu kien d|a chat v i tidu chuan thiet ke d Viet Nam; (2) Thiet ke thd nghidm mdng eda cac d y an ket cau hien tai sd dyng cpc ong thep de so s i n h giQa cpc dng thep va egc thyc te dang ap d y n g ; (3) Xdy d y n g So tay Hudng d i n t h i l t kd Cpe dng thep.
2. Dgc d i e m dja c h a t d Viet Nam
Vidt Nam cd hinh dang l i mpt d i i dat hep keo d i i td Bac den Nam. Dien ticli dat khoang SSO.OOOkm^. Cd s6 hg tang v i c i c dU i n ODA hd trp eho sy p h i t t r i l n n i n kinh t l chd y l u la Ha Ndi va khu vuc TP. HCM.
Hinh 1. Dgc diem dja chat d Vidt Nam va Nhgt Ban C i e t i i lieu nghidn cdu d|a chat eda Hiep hdi Dja chd't Nhat B i n , Hidp hdi Ky sU cdng trinh Nhgt Ban va c i c tai lieu thu thap cua Nhdm nghidn c d u chd y e u dupc t i i n hanh d H i Ndi, T P . HCM v i D d n g b i n g sdng Cdu Long. NhU d (Hinh 1), chia eae Idp dat t h i n h Idp da't chju lyc ed chf s d SPT > 30, Idp dat b l mat va Idp dd't trung gian 6 cae khu vuc mien Bac, Trung, Nam: 6 Mien Bde, ldp dat ehju lyc bao gdm dat cat va cudi sdi ehidm tUdng doi idn d dp s a u khoang 30-35m, cd n h i l u Idp dat xen ke la eat va dat dfnh cd gia trj N t d 6 - 7 , Idp dat y e u tim thi'y chu y l u d Idp d i t b l m i t d c h i l u d i y t d 12-15m; 6 m i l n Trung da phong hda chiem ty Id Idn cda Idp dat chju lUc; 0 khu v y c T P . H C M va D d n g bang sdng C d u
KHOA HQC - CONG NGHE
Long, Idp dat chju lye ehd yeu la di't cat v i da't dinh 5 dp s i u t d 15-60m, Idp d i t be mat la d i t yeu cd c h i l u day Idn den 40m v i gia trj N td 0 ~ 1 . Ket qua d i l u tra gidng kd't q u i khao s i t trong cac t i i li§u nghien e d u , eau trdc d|a tang eda Vidt Nam khac nhau gida cae vdng mien, cdn v l loai da't thi cd b i n gidng nhau [1,2,3,4,5,6,7].
3. Phan tfch sdc khang cpc dng thep ddng trong dieu kien dja chat Vigt Nam
T i l n hanh so sanh ket q u i thd t i i eda cpc dng thep ddng trong nen dat thyc te cua mdt sd dU i n d Viet Nam vdi sdc khang cua cpc dng thep tfnh theo cdng thdc cda Tieu ehuan thidt ke Cau dUdng bp Nhdt B i n {Tieu ehuan N h i t B i n ) Tuy nhien, e i c ket q u i thd t i i n i y khdng thu dupe sy phan bo iyc dpe tryc vi cgc dng thep thi nghiem khdng dUpc gan e i c dau do bien dgng. Do d d , tgm thdi d i n h gia sde k h i n g mui cpc v i sde khang ben cpc rieng bang each x i y dung dudng cong quan hd T i i trpng - Dp Idn td md hinh phan tich vdi h i n g sd Id xo nhU 6 Hinh 2, sau dd so s i n h nd vdi cae so lieu thd t i i .
Md hinh p h i n tfch dgng phi tuyen dUdng cong Ma s i t thanh cpc - Chuyen vj v i dUdng cong Sde khang d i u coc - C h u y i n vj vdi Id xo the hien ma sat t h i n h cpc dat d gida eac Idp dat va Id xo the hidn sUc k h i n g m u i epe dgt d mui cpc. Hdng s d Id xo dUdc tinh t o i n t d s d lidu dia chat trong thd t i i d Viet Nam va dudng kinh n g o i i cda cgc d n g thep theo T i e u chuan Nhgt B i n .
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Trong Hinh 3, dd thj ehi ra rang dUdng cong quan hg gida T i i trpng d i u cpc va Chuyen vj dau cpc qua k i t q u i p h i n tich theo Tieu c h u i n N h i t Ban va kd't q u i do dupc l i trdng nhau t d gia trj t i i trpng b i n g khdng (0) d i n gia trj t i i trgng Idn nha't. Do dd xet den tac dyng eda t i i trpng Idn n h l t , sde khang eda cpe dng thep ed the dupc ude tinh kha chfnh x i c . S y phdn b d t i i trpng d i u cpc cho thanh cpc bang 4 0 % sdc khang ben eye han v i cho mui cpc la tUdng ddi nhd, x I p xf b i n g 5% sdc khang mui eye han.
4. Nghidn cdu sdc khang cpc dng thep trong dieu kign dja chat Vidt Nam
D l l i m ro cae v i n de thiet k l lien quan den sde k h i n g cda cpc dng thep d Viet Nam, Nhdm nghien cdu da thye hien t h i l t ke so sanh s d dyng tidu e h u i n thfeh hpp cda N h i t B i n v i Viet Nam.
4.2. S y khac nhau ve ket q u i thiet ke tuin theo cac tieu chuan thiet ke khac nhau
De phan tfch s y k h i e nhau trong t h i l t ke kItcSu mdng cpe tuan theo cae tidu c h u i n thiet k l kh^c nhau, Nhdm nghien edu thuc hidn mdt t h i l t kiso sanh gida Tieu c h u i n Vidt Nam v i T i i u chuin NhSt B i n , k i t q u i n h u d B i n g 2.
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Tidu chuan Nhdt B i n qui djnh kiem tra sdc k h i n g , d d b i n v a c h u y i n v i ngang cda cgc vdi tat ea cac td hpp t i i t r p n g theo c i c trgng t h i i gidi hgn s d d y n g , c y d n g d p v i d a c bigt (ddng dat, va tau). Trong khi dd, T i e u ehudn Viet Nam qui djnh kiem tra e h u y i n vj ngang, dp ldn eda epe vdi td hpp tai trpng theo trgng t h i i gidi h g n s d d y n g , c d n sdc k h i n g , dp b i n c u a cpe dupc k i l m tra vdi td hpp t i i trpng 6 trgng t h i i gidi han cudng dp v a d g c bidt. Hdn nda gia tri cho phep hay gia trj sdc khang eho nhdng dieu kidn kiem tra nay c u n g khac nhau trong tdng tidu chuan.
Thidt ke so sanh da dupc thyc hien cho b i y (7) k i t e l u hidn c d d Vidt Nam s d d y n g ket cau mdng egc ddng (kd't c l u c a u dudng bp, cau dudng sat, nha v i c i n g ) .
Kd't q u i nghien c d u thidt ke va kd't q u i so sanh dupe the hidn d Hinh 4 . C d t h i nhan xet rang, n h i l u trudng h p p thiet k l m d n g epe d n g thep theo Tieu chuan Nhdt B i n khdng thda m a n gia trj cho phep v l sde khang qui djnh trong eae tieu chuan Viet N a m , mgc d u c i e dieu k h o i n k i l m tra ve cUdng dp c p c , c h u y i n vj ngang cpc v i Idn vdn thda m a n .
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Hinh 5. So sdnh sUc khdng thiit ki w Do d d c d t h i nhgn thay rang, s d c k h i n g thidt k l eda c p c x i e djnh theo n i n dat cd s y khac nhau rd ret theo c a c tidu c h u i n thiet k l dupe a p d y n g . Hinh 5 so s a n h s d c khang thidt k d theo Tieu c h u i n Viet Nam vdi Tidu chuan Nhdt B i n cho bay (7) d u a n . Sdc k h a n g c d a c p c d n g t h e p thidt ke theo T i e u chuan 2 2 T C N 2 7 2 - 0 5 v i T C X D 2 0 5 - 9 8 , l l n lUpt nhd hdn so vdi T i e u chuan Nhat B i n l i 3 0 % d e n 6 0 % . Dieu nay
l i do c d s y khae nhSu ve he s d sdc khang d y a tren g i i trj N v i he s d an toan ddi vdi sdc khang cue hgn.
Nhu de cap d t r e n , sdc khang thiet ke dupe tfnh t o i n theo Tieu chuan Nhgt B i n Idn hdn so vdi thiet k d tinh toan theo Tieu ehuan Viet Nam ( 2 2 T C N , T C X D ) . Do d d , neu ap d y n g tieu chuan Nhgt B i n , cd t h i g i i m dUpc s d IUpng cpc y e u c a u . Neu v g y , cd t h i t h y c hien dupe thiet ke kinh te hdn. Trong bdi c i n h n i y , t h d thach dua ra la i p d y n g cdng thdc tfnh sdc khang theo T i d u e h u i n N h i t B i n sao c h o dgt dupe m p l thiet k l hdp ly, edng thdc nay da dupc khang djnh tinh chfnh xac trong cac ket eau mdng d Nhgt B a n .
4. Kd't ludn
Qua e i c k i t q u i nghien cdu trinh b i y d trdn, cd t h i tdm tat nhOng v i n d l da dUdc l i m ro v l phuong phap thiet ke cpc dng thep d Vidt Nam n h u sau:
- Tieu chuan thiet ke Viet Nam tham khao rdng rai e i c tieu chuan thidt ke eda nhieu qude gia. Viec l y a chon tidu chuan thidt ke tuy thupe vao ehu dau tu, khdng ed s u bat budc ap dyng tieu e h u i n ey t h i n i o eho k i t cau.
- Hien nay, cd the ndi rang thiet ke cpc dng thep dua tren Tieu chuan Viet Nam an t o i n hdn nhung it kinh te hdn so vdi thiet ke dUa tren Tieu chuan Nhgt B i n . Di dat dUde mpt thiet ke hpp ly, d y a trdn Tieu e h u i n Nhdt B i n da dUde khang djnh tfnh ehfnh xae, can phai xem xet va nghien cdu d l dua ra mpt cdng thdc tfnh toan sde khang cpc d n g thep hpp ly hdn trong dieu kien dja c h i t Viet Nam G
T a i l i e u t h a m k h i o
[1]. Takao Nakano: Characteristics of Vietnamese Ground; Foundation Work pp. 3 1 - 3 4 , June 2007.
[2]. Sakae Takada: Soils of the Mekong Delta on Indochina Peninsula (Southern Vietnam); Foundation Work pp. 3 5 - 4 1 , June 2007.
[3]. Masanori Tanaka et al.: On Characteristics of Sedimentary Structure of Mekong Delta Cohesive Soil—Example of Can Tho, Vietnam; 41^' Meeting for Reading Research Papers of the Japanese Geotech- nical Society, July 2006.
[4]. Yoshiki Yuasa et al.: Evaluation of Strength of Sedimentary Clay (Can Tho Clay) of the Mekong Delta; 4 1 ^ Meeting for Reading Research Papers of the Japanese Geotechnical Society, July 2006.
[5]. Kyushu University Press: Special Soils of Kyushu/Okinawa; p. 29, July 1983.
[6]. Soichiro Nakamaru et al.: Strength/Deforma- tion Characteristics of Various Types of Sand in Sin- gle-Plane Shear Test; Collection of Papers Read at Symposium of Japan Society of Soil Engineering, p p . 1 1 1 - 1 1 8 , 1995.
[7]. Nhdm nghidn edu Dai hpc Giao thdng vdn t i i : Report on Collection and Investigation of Preliminary Data, October 2010.
[8]. Nhdm nghidn c d u Dgi hpe Giao thdng v i n t i i : Report on Application of Steel Pipe Pile in Vietnam, May 2 0 1 1 .