i-^Ai.H
65-5^
Danh gia SLFC chju tai cua dat nen
du'O'i mong nong cho khu vyc dja chat tinh An Giang
Ngay nhan bai: 20/8/2014 Ngay siia bai: 25/8/2014 Ngay chap nhan dang: 10/9/2014
T O MTAT:
N<>i dung b ^ bdo niy tap trung vao vi^c phan tich so sdnh cac phfltJng phap tinh toan sflc chiu tai dat nen. Cac phfldng phap tinh toan ^di tich vd phfldng phap phan tfl hflu han vdi sfl h6 trd cua phan mem Plaxis dflflc sfl dung de i ^ e n cflu phan tich tuih todn sflc chiu tdi ciia ddt nin theo cdc thong so tfl thi i^hi^m ddt trong phong. Ket qud xde dinh sflc chiu tai ciJa dat nen tinh todn tfl cdc phfldng phap nay dfldc so sanh vdi nhau va vdi ket qua thi nghidm bdn nen tinh hien trfldng de nit ra cdc kit luan tren hai loai dat cdt pha vd set pha.
Kit qud phdn tich trfin hai loai dat nay cho thay rang phfldng phap phan tfl hflu han sfl dung mo hinh Mohr Coulomb de tinh todn sflc chiu tdi cua dat nen dfldi mdng ndng co do tin c^y cao nhat gdn dung vdi thi ket qua nghiem tfl ban nen hien trfldng (sai l^ch 3%). Kit qud tinh todn theo cong thflc SPT (phfldng phdp MeyerhofF) va Eurocode 7 cho ket qua thap nhat va cao nhat tUdng flng. Cung co the nhan thay rang khi sfl dung gia tri sflc chiu tdi theo TCXD 9362:2012 nen chon cdc he so dilu Id^n ldm vile dong thdi gifla nen va cong trinh theo can trin.
ABSTRACT
The content of paper concentrates on comparison research of the bearing capacity of the soil below shallow footmg determined from different methods. Analytical methods and finite element method (FEM) supported by Plaxis software were used to obtain the purpose of this research. Also, the bearing capacity of the soil determined from these mediods was compared each other and with result of Plate Load Test in-situ which is considered as an accuracy method to give conclusions of this research on clayey sand and sandy clay soils. Analysis result on these soils gives that the bearing capacity of the soil determined from FEM was more accurate method than other methods. These methods are different about 3% as compared with plate test result in situ. The result obtained from SPT (Meyerhoff method) and Eurocode 7 calculations give smallest and highest values respectively. It can be realized from this study that interaction factor between superstructure and foundation should be selected in upper limit as using TCXD 9362:2012 standard.
TS. NguySn Minh Tdm - Giang vien
Khoa Ky Thuat Xay Dflng, Trddng Dai Hoc Bdch Khoa - Dai Hoc Quoc Gia Tp.HCM Email: [email protected]
Di?n thoai: 0903863348
KS. Nguyen Thanh Qui - Hpc vien cao hpc
Khoa ky thudt Xay dflng, Trfldng Dai Hpc Bdch Khoa - Dai Hpc Quoc Gia Tp.HCM Email: [email protected]
Dien thoai: 0989897151
Nguyen Minh Tam, Nguyen Thanh Qui
I.Gidithifu
Trong thiet ke nen mdng cdng trinh viec xac dmh sflc chju tdi an toan va chinh xac cita dat nen la rat phflc tap va no anh hi/dng rit Idn din an nguy cua cong trinh, tfl luc mdi xay dflng cho den sudt qua trinh lun diin tien vd suot qua trinh ton tai cua cdng trinh, sflc chju tdi c6 khuynh hudng thay doi. Hi^n nay cdc cong trinh thu'dng di/oc tinh toan va thiet ke sao cho hieu qud nhat ve mdt kinh t l , xem nh^
v l mat giai phdp ky thuat lam gidm bdt tinh chinh xde (dac bilt la v l vi6c tinh todn sflc chju tdi cOa dat nen) nen cd nhieu cdng trinh sau khi da xgy dflng xong va dUa vao sfldung mot thifi gian thi xdy ra cdc sU cd nhU: lun, nghi^ng,...
Trong vai chuc nam qua c6 kha nhilu phuong phap ude luong sflc chju tdi dat nen dat ciudi mdng nong nhU: Phu'ang phdp han chl vOng biln ciang d^o, phuong phap gid thuyet mat trUOt phdng ben dUdI day mdng la mat gdy phdng, phuong phap can bdng gidi han diem trong pham vl nen dat ngay sat dfldi day mong. Cdc phflong phdp tinh ndy deu dfla vao gid thuyet dat la vat lieu dan hdi, dan-d^o, cflng-d^o.Tuy nhien tinh chat cua trong thflc te lai vd ciing phflc tap nen khi dp dung cdc phuong phap tinh toan sflc ch[u tdi thi kit qud se sal lech vdi sflc chiu tdi thuc cua nen dat
Xuat phat tfl nhflng y^u cau thflc te neu tren va k l thfla cac nit qud nghien cflu cCia cdc tac gid tren t h i gidi, tac gid da tap trung phdn tich so sdnh sflc ch[u tdi dat nin thdng qua cdc phu'ang phdp khdc nhau dong thdi so sanh cdc ket qud ciia cdc phuong phdp vdi kit qud sflc chiu tcii tfl thi nghiem ban nen hiln trudng d l dlic kit ra cac kit luan flng tJung cho cdc ky sU tu van thilt kl, qudn ly dfl dn va thi cong cong trinh.
2. Phfltfng phap hif n trflcAig xac dinh sflc chiu tdi
2.1 Xde dinh sifc chiu tdi theo thi nghiem SPT ' '
Thi nghiem xuyln dong chuan SPT duac tiln hdnh v ^ toe do nhanh tuong flng vdi phuang phap thf nghiem c3t nhanh khong thodt nu'dc. Do vdy, kit qud SPT tien td dung
93
flng xfl ciia ddt riH, cdn vdi d i t dinh nd d i l n td dung flng xfl tflc thdi va khdng dien td tot flng xfl lau dSi cua dat dinh. Tuy vdy, theo ty t h u y l t cO hpc dat tfli han va thUc nghiem chflng t6 rdng vdi dat dinh cd ket thudng (NC) thi sflc chju tai tflc thdi se bd hdn sflc chiu tdi lau ddi, vl trong qud trinh chju tdi hd sd rdng cOa dat se gidm, dong nghia cdc dac trUng chdng cdt tang len.
Terzaghi vh Peck (1948) tfnh toan sflc chiu tdi ddt nen cdt theo thi nghigm SPT flng vdi dp lun dat nen bang 2,54cm. Sflc chiu tdi xac dinh tn/c tiep sflc chju tdi q , t f l toan do theo hinh 1a.
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Hinh 1 Tojn d6 xic dinti sij'c ctilu til cda mong niing vi xac dinh he so N N trong cong thii'c tinh Silcchjutaitrfti nen cit
Hoac cd the dua vdo do thi hinh 1 b tra cdc he sd vd roi dp dung bleu thflc 1 xde dinh sflc chlu tdi.
qu=qNqFqsFqdFqi-l-0,5BNyF.^.|^Fy, (1) Trong b i i u thflc 1 cSc h^ s l F^,, F ^ F^,, F^, F ^ F^, ISn lUOt Id cac yeu to
x6t d i n dnh hudng ciia hinh dang mdng, phflong tde dung cila tdi trpng.
Tfl thUc nghiem Meyerhof (1956) da d l nghi bieu thflc 2 vd 3 Ude luong sflc ehiu tdi flng vdi do liin 2,54cm.
b > 1 . 2 2 m ^ q , ( ^ , j , [ K N / m 2 ) . 7 , 9 9 N ( ! g ^ y (2)
(3) Trong b i i u thflc 2 vd 3 thi N flng vdi s& biia cCia thi nghi&m SPT cdn b 1^ b l rong m6ng tinh bdng m.
Khi x l t d i n dieu k i l n lun eiia mong eung vd^ do sau chon m o n g xae dinh qua b l l u thflc 6, Bowles [1977) de nghj cong thflc h i f u ehinh xde dinh sflc ehju tdi cd dang b i l u thflc 4 vd 5.
b<t.22m=>qa(r,et)!KN/m"') = 19,16NFd
F d = l + 0 , 3 3 ( D f / b ) < 1 , 3 3 j ^ j 2.2 Xde dinh sde chiu tdi theo thi nghidm bdn nin tinh
Thf nghi$m ban ndn tTnh dUOc xem Ici phuong phap co do tin cay cao nhdt de xde djnh khd nang ehiu tdi tdi cua ddt n i n . K i t qua chinh cua thf nghiem nay Id quan he gifla do liin va ede cap dp luc. Thong qua quan he ndy ngUdi thiet ke ed the xde djnh dupc sflc chiu tai cho phep ciia dat n i n , t f l do k i l m tra vd ddnh gid do an todn, do on dinh cho n i n khi chju tdi c6ng trinh
Thi nghidm ban ndn hien trUdng la tang tcii tflng cap len ban nen, do ehuyen vi dflng on djnh cua bdn nen flng vdi tflng cap tai trong, cho d i n 10c dat tdi trong tdi han P^.Tdi trong tdi han duqc dmh nghTa la flng vdi tdi d d chuyen vj dflng ciia ban ndn khdng gidm dan v l dn djnh (gid trj dn dinh thudng duac chon khi trong khodng thdi gian 1 g i d d o l u n n h o h o n 0,2mm).
OuDng cong M b i then tMI gian
(4)
(S)
Hinh 2 Bieu do d6 liin theo (tiiii gian va do liin theo theo dp t^i
Do ban nen dUOc md hinh la m d t m o n g nong t h u n h i , nen t f l k l t q u S thi nghi6m duoc the hi^n bSng d u d n g cong quan he gifla b i l n dang vd thdi gian: 5-t; Tdi trpng vd bien dang: P-S lan luat trong hinh 2. Thdng qua bieu d d quan h f giflu d p lun va tdi trpng hinh 2, ta cd t h i xac djnh dUpc ung sudt gidi han cua d i t n i n theo cdc each n h u sau.
- Cdch 1: Cfng suat gidi han ciia ddt nen Id giao d i l m eiia hai nhanh dan hdi vd d l o eiia dudng cong ndn l i i n .
-Cdch2:P = P , n e u 2AS,,sAS£AS|^,
Vdi: AS,^, - sd gia do lOn do cap tdi P^^, gay ra.
dS| - sd gia do lun do cap tdi Pi gdy ra.
AS,,, - sd gia dp lun do cap tdi P,, gay ra.
Hay ndi cdch khdc P ^ Id cdp dp Iflc nen ma gia sd d d \iin flng vdi cSp ap lue P, Idn gcip ddi gia sd lun vdi cdp dp Iflc ke trudc P,,, dong thdi bang hoae nhd han gid trj flng vdi cap P^^,.
- Cdch 3: Li cSp dp Iflc ma tai d d dd lim flat gid tr| quy ude bSng 1/10 d u d n g kfnh bdn nen trdn hoac canh eiia ban ndn vudng.
3. Phfl<nig phap difa tr£n mflc tfd phdt t r i l n cOa viing b i l n dang ddo trong n i n
Ndi dung chflng minh eiia phuang phap dua t r i n qui ludt cdn bang deo Morh-Coulomb nhdm han c h l vCing b i l n dang ddo trong pham vi nen sao cho ddt con flng xfl n h u mpt vat lieu dan hdi de eo t h i dp dung cdc k i t qud ly t h u y l t dan h6i vao tfnh todn flng suat trong n i n .
Khi dp luc ddy m d n g p du nh6 nen con Ong xfl Id vdt lieu ddn hoi. Ap lu'c p tSng ddn v i i n g bien dang ddo t r o n g nen v i i n g b i l n dang ddo trong n i n bdt dau xudt hien t f l hai bien ddy m o n g va khi p dii Idn thi edc dilm bj b i l n ddo chay tren vdng (L) (co eao trinh t f l D , d l n (D,+ Z = D, + 0.5b) n h u t h e h i e n d h i n h S .
VOng deo M(Z)
Hinh 3 Viing d ^ dir^ mong bang
Khi dieu kien can bdng Morh-Colum thda m a n thi cdc d i l m sau nhdt CO trang thai cdn bang gidi han d l o nam t r i n mpt dfldng C d i l n td bfli phuong trinh: Z^^, = f[2p,p)
Vd tifng sudt cua nen dat flng vdi d p sdu dat trang thdi can bdng gidi han luc nay duoc xde djnh tai bieu thflc 7.
Pimax = - ^ ( 7 Z m a x + Y D f + c c o t g t p ) + Y D f
cotg tp-Hp- (7)
Khi t i n h todn sflc chm tdi ciia nen theo trang thdi gidi han ve biln dang, de d d lun ciia mong cd sai sd nhd, nen dat phdi cdn hoat dong nhU vat lieu bien dang dan hoi. Do d d sflc chju tdi cOa n i n duac chon tflOng flng vdi vimg b i l n dang ddo phdt t r i l n t f l ddy m o n g den d l sSu Z ^ = b/4. NOI each khde, vdi hai v l t nhd bien dang d l o ndy, nen cd t h i c6n
g4iaDni:[iai 10.2014
dflpe xem n h u la bdn khdng gian bien dang t u y i n tinh.
Theo ly ludn tren sflc chju tai dupc xae dmh n h u sau:
- y - . + yDf-i-ccotg<|» + Y D f
^ m a x ^ 4 cotgiJ»+(l(- (9)
Trong tidu chuan 45-70, cong thflc nay duac gidi thigu dfldi dang sflc chiu tdi tieu chu^n ciia ddt nen xac djnh theo cdng thflc sau:
R*' = m ( A b y , + BD^y^+Dc) (10) Sflc chiu tdi tidu chuan trinh bay trong tieu chudn 9362:2012 da dUpc
xet thdm dieu kien ddng t h p i giOa n i n va cong trinh va duoe gpi la sflc chiu tdi t i n h todn theo trang thdi gifli han t h f l hai R„ ciia ddt nen.
R „ = ( A i D y „ + B D ^ y ' _ - F D c J ( , , ) 4 . Phi/cmg p h a p cdn b d n g g i o i han d i e m t r o n g p h a m v i nen d a t
ngay sdt d u d i d a y m d n g 4.1 Bai todn phing
Trong t r u d n g hop chung ciia trang thai gidi han ddi vdi bdi todn phang ngUdi ta xdt sfl can bang eiia phdn to dat hinh vudng trong he tpa d d vudng gdc yOz, c h i l u d u o n g cOa Oz hudng theo e h i l u tac dung cua trpng Iflc. Phan t d dat co canh d^ va d^ chig tde dung ciia cdc utig suat a^
o^ va T^ va t r p n g luong bdn than n h u t r o n g hinh 4.
<g*jiitj{j yy/'/Hi
Hinh 4 S(f do ling suat tde dung trong bai toan phang
Trang thai cdn bdng ciia phan t d dat duoe b i l u thj bdi hai phuang trinh VI phdn cdn bang tinh vd dieu kien cdn bdng gidi han k i t hpp thanh he phuong trinh.
atyz 52 (az-
"y + y = o
dy
-Cyf+4T^Z ,,„
(az+CTy2cotgtpT
4.2 Bdi todn Ifhdng gian
Bdi todn khflng gian chi co he p h u a n g trinh vi phdn cdn bSng ddi vdi hai bai todn d d i xflng true. Ddi vdi bdi toan ndy ngfldi ta d i i n g he tpa dp hinh t n j t r o n (r,9) vdi cdc ky hieu ciia cac thanh phan flng suat n h u tren hinh 5.
4.3 Ldi giii eua Prandlt
Prandtl quan sdt trflc tiep hinh dang cdc m5t trUpt dat n i n ben dUdi mo hinh mdng va gidi he phflong trinh 12 v<M gid t h u y l t khong xit t r p n g lu'png dat nen y = 0. sflCchju tai dat nen dflpc t h i l t lap nhU sau:
q . , = ( y D , + c . c o t g t p ) J ± § | e ^ - t g ^ - c . c o t g < p (13) 4.4 Ld)' gjdf eua Sokotovski
Sokolovski dua gidi hd p h u a n g trinh 12 eho bdi toan phdng cd xet d i n trong luong eiia dat. Bieu thflc Xokolovxki chi d i m g duac cho cdc m d n g dat nong, vi luc do co the thay Idp dat trong pham vi dp sau dat m o n g D bang tdi trpng ben.
Hinh S Sodo i}ng suat tac dung trong b^i toan Miong gian
Hinh 6 Dang mat trUtrt dudi miing ciia Soholovski
Trong hinh 6 cdc mat t r u o t ed dang hyperbole. Dua vdo cac d i l u kidn bien eu the hd phUOng trinh tren dUpc gidi cho cdc cong thflc xae d m h sflc chiu tdi cflc han cua dat nen dudi mdng nong q^,^ cOa Sokolovski la:
<iuii=Pr(<=+'itg<p)+q (14) 4.5 Ldi gidi c^a Berdzdnev
O i l m t i l n bo ciia phuang phap nay la xet d i n sp t o n tai c i ' - ' ' ^ ^ dat dudi day mong. N6i dung ciia phuong phap Berezdnev " ^^^ ^^^^
phuang phap cua Sokolovski de tfnh toan cdc dUdng t n ' - " "^^^ ^^^'~ ^^^
tren thUc nghiem mo hinh de dOn gidn hoa d u d n p ' - ^ d t bang t i n h todn Trong so do tfnh todn ciia P^rezdnev xdt tdi -^f^ '^at la tam gidc vuong can va xet can bang cOa cic doan va n p - ^^^ '^^ *""'" ^^^ <^hiu tdi gidi han.
Trong ldi giai bdi Joan phans> c^" trpng cjidi han phan b d deu theo bleu thflc 15.
Qu ^ N y n . y P + N q n - q + Ncn-c (15) Trong bd'tosn khong gian doi xflng true, tdi trpng gidi han t r u n g binh
d i / o c x d c ^ n b n h u s a u .
q u - N y k - T - B + Nqk.q-i-Nck-'= -{16) Trong bai toan mong chfln sau vfla, tdi trpng gidi han len n i n cdt dUOe
v ^ t lai dudi dang.
q u - A ^ . y - b (17) 4.6 Ldi gidi eua Terzaghi (1969)
Terzaghi da de nghi mpt ldi gidi tiep theo Prandtl.Terzaghi dd xde dinh cac he so sflc chiu.tdi t i i d u n g ludi dudng trUOt ciia ddt khong t r p n g luanq n h u ^ o exi nhan cflng tam gidc khac phuc sflc khang bj d p n g cua dat theo nhflng mat trflcrt thdng.
Theo gido trinh Ca hoc dat, Chau Ngpe An (2012) da phdn tich vd chflng rninh. Sflc chiu tdi ciia dat nen theo Terzaghi g o m ba thanh phan:
Tbanh phan ma sdt dfldi day mong, thanh phan phu tdi h o n g , thdnh phan lUc dinh.
Trong ldi giai bai todn phSng, phflong trinh sflc chiu tai ciia dat n i n
10.2014BnElffi[|ail95
dudi mdng bang ciia Terzaghi dupc t h i l t ldp theo cong thflc tinh sau.
q u = ^ Y B N y + c N c + q N q ,18) Trong bai todn khdng gian ddi xilng true, ddi vdi m o n g dang hinh
vudng theo Terzaghi sflc chiu tdi cOa n i n ddt cd dang n h u sau;
q u = l , 3 c N c - H q N q + 0 , 4 y B N y (19) 4.7 Ldi gidi cua Meyerhoff (1956)
Phuang phdp nay dupe Meyerhof khdi xUdng co xdt den n h i l u thdng sd Idn sflc chju tdi cOa ddt n i n , vao nhflng nam dau cua thap ky 60, the kJ 20, trong cdc n g h i l n ciifl cOa n h i l u tde gid khdc nhU: De Beer (1970), Vesic (1973), Hansen (1970), ,...da xet d i n dnh hudng cdc y l u t d : hinh dang m6ng len mat trUpt nhU hinh 7, do chon sau eua mdng, dfl nghidng ciia mong.
tich bdng phuang phdp ph£n t&hOu hgn.
Mo hinh hinh phan sflc chju tdi ddt n i n d u n g phdn m i m Plaxis dupe t h i hien d hinh 9 trong d d dp d i j n g t i n h chdt bdi todn b i l n dang phdng dupc dp d y n g . Qud trinh xde d j n h sflc chju tdi duoc phdng gifing md hinh ban n^n ngoai hidn t r u d n g .
Oe thflc hien t i n h todn va so sanh vdi k i t qud phan tfch ta-ln nhieu loai flng xfl mfl hinh cua dat, trong m o p h d n g ndy m 6 hinh dat Id Mohr- Couiomb (MC) dUOe chpn Ifla de phan tfch.
6.3 Xde dinh sde ehiu tdi bing phuang phdp sS.
Tfl hinh 9 ket qud phdn tfch bdi todn theo phdn mem Plaxis dupe d u d n g cong quan he gifla chuyen vj cua ddt n i n vd tdi trong nhu bieu do hinh 10.
Hinh 7 Dang mit trUot tmng ding thiit dia Meyerhof
Cflng thflc sflc chju tdi d i t n i n dudi mflng nflng liic nay xac dinh theo b i l u thflc 20.
qu = cNcFcsF<.(jFci + qNqFqsFq^jFq, + Q.SybH^Vyf^^^^ (20) 5. Phuong p h d p g i d t h u y l t m d t t r i / p t p h ^ n g ben d i / d i ddy m d n g i d m d t g d y p h i i n g
Terzaghi vd Peck (1948) da gid thuyet mat trUcrt dudi dien chiu tdi cue han bi trUpt theo hai mat phdng AB va BC nhU hinh 8.
(21) Hinh 3 Dang m|t tnr^ pIrSng dirdt day mdng
Peck da chflng minh rilng cho cdc loai nen dat va t h i l t lap bieu thflc tdng qudt tinh sflc chju tdi cflc han cfla dat n i n xde djnh nhU:
P u - Y D f N 9 + 7 k 2 ( ^ - l ) - v D f N q - f Y ^ N y Trong b i l u thflc 21 cdc gia tri N va N duoc xde dinh:
N^=tg'{45°+<p/2) vd N^ = Nq-1 6. Phuwng p h d p sS xde d i n h sflc c h j u t d i 6.1 Md hinh Morh-Columb
M f l hinh Mohr- Coulomb t r o n g Plaxis dupc dua tren y tudng ciia quy luat CO bdn dan - d l o vdi mat ngflging c6 djnh khong bj tac d£ng bdi b i l n dang d l o va trang thai li'ng suat cua mpt d'?m ndm trong mat ngfldng la Hinh 9 Mo hinh phan tich tinh toin iifc chiu \l\ flat nen bina - . , . . - <.. t . - n, . ,n 0,2 Mo limn phan
Plaxis 2D '^
- ^ -
Hinh 10 Bi^u do quan he do lun va tii trong
Thdng qua bleu do hinh 10 sflc chju tdi xde djnh la giao d i l m ciia hai nhanh dan hdi va d l o ciia d u d n g cong nen lun.
7. Phan tich so sanh giiita cdc phtfcmg p h d p t f n h t o d n sflc. chju tdi cOa d a t n e n t h e o tCAig c d n g t r i n h .
7.1 Phdn tieh sde chlu tdi theo cdcphUOng phdp Cdc thdng sd dia chat cua cflng trinh Trudng trung hpc ph6 thflng Cfl To, An Giang sfl dung mo hinh MC t r o n g phan m i m Plaxis de mo phflng cho flng xfl ciia cac Idp dat dUpc t o n g h p p d bdng 1.
Tfl cdc so lieu dja chat ciia cdc cong trinh tai khu vuc n g h i l n cflu t i l n hdnh tfnh toan phdn tfch sflc ehju tdi theo cac phuong phap phdn tieh neu trdn K i t qua t i n h toan ndy cila cdc cdng trinh so sdnh vdi k i t qua tir thi nghiem ban ndn hien trudng thanh lap hai b i l u d d c h i n h Ideh cho hai loai dat cat pha (hinh 11) va set pha {hinh 12).
Bdng 1 Thflng so eiia eac Idp dat sfl dung m d hinh IVlohr-Coulomb a c chl lieu
(IngxClvatUiu Dung i r o n g t r ^ ITILIC nuAc ngim Dung Irong dUiJi mi/c nudfc ngSm He s6 I t t i m L u c d h h Goc n o r m a sat G6c gian nd M6 Oun Young (ai be m^I ldp H i sS Poisson He sfi tuong t ^ giua dSt va k^> t j d - -
Kyhieu
T — T - K C V V Eief V R n
Dem VI
kN/m'
mm'
cm/day kPa deg dfg kPa
Cat pha Drained 1B,S0 19,66 1 9 30 0 23m
0,3 1
S«tpha Undrained
20,00 20,02 l,0E-O3 32 14 0 9200 0,3S 1
CAph3 DialnEd 19.S0 19,89 1 9 28 0 2700P 0,3
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Npi d u n g n g h i l n cflu tap t r u n g vao vide so sdnh vd ddnh gia cdc phflong phdp tfnh todn sflc chju tdi ddt nen bao gdm phflong phSp giii tich, p h u a n g phdp phan t f l h f l u han t f l m o hinh IMC. K i t qud phdn tich ndy cung duoc so sanh vdi k i t q u d ban ndn tTnh thuc t l tai cflng trinh. Cac kSt
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Soaety of Gvil Bigineers, ASCE journal for Soil medianics and Foundation Engineer, Vol.S2, S M I , 1-19.
6. Terzaghi K, and Peck R.B. (1948), Soil Mechanics in Engineering practice ,Jonhn Willy, New York.
7. Terzaghi, R.B (1969), Foundation Engineering (2nd Edition), Jonh Willey and Son, New York, S14p.
S. TCXD45-70(197S), Tieu chuan thiet he nen thien nhien (ho nha v^ cong t r i n h . Bo xSy dung 9. TCXD 93612012 (2012), tieu chu^n thie't ke nen nha v^ cong n i n h . Bo xay dung 10. Veic, A.S (1973), Analysis of Ultimate Load of Shadow Foudalion, JSMFD, ASCE, Vol.99,
H'inh I I Bieu d6 chSnh ISch {%) cdc phuong phap so vdi k f t q u i ban nen doi wSi Sit nen toai loai Cat pha, trang t h i i ch|tvOa
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Hinh 12 Bi^u do chenh lech (%) cac phumig phip ;o vfH het qui ban nen M vol dat nen ioai lof I S^t pha, trang thii ni}a (ling
ludn t f l d e tdi n g h f i n cflu nay c6 t h e duoc due k i t n h u sau:
Ofli vdi hai lo^l ddt: Set pha, trang thai nfla cflng vd Cat pha, trang thdi chat vfla thi k i t qud phdn tfch sflc ehiu tdi theo mfl hinh MC dang tin cdy nhdt chenh lech vdi k i t qud ban nen hidn trfldng chi khodng 3%.
Vdi k i t qud sflc ehju tdi ciia nen t i n h theo SPT (Meyerhof, 1956) cho k i t qud t h d p nhdt c h i n h lech vdi k i t qud bdn nen khodng -40% vdi dat n i n loai cat pha. Con ddi vdi dat nen loai set pha thi do chdnh lech nay cao hem nfla khodng -60%.
Ben canh d d thi khi t i n h theo Eurocode 7 k i t qud cao nhat cao hon k i t qud ban ndn. Oo do k i t qud sflc chju tdi ed t i n h chat tham khdo khi t h i l t ke edng trinh d d i hfli eao ve hieu qud kinh t l cho phan m d n g eflng trinh.
K i t qud tfnh todn theo TCXD 9362:2012 c6 gia trj chenh lech vdi k i t qud ban ndn theo cdn dfldi. Do d d khi sfl dung gid t n sflc chiu tdi theo TCXD 9362:2012 ndn chon cdc he sd d i l u kidn ldm vide dong thdi gifla n i n va cong trinh theo cdn trdn.
TAIUEUTHAMKHAO
1. Bowleg I E . (1977), Foundation analyis and Design, McGraw-Hill, New Yofk, 2. Chau Ngoc J n (2012), Co hoc dat, NXe OHQG Tp.HCM.
3. De S e a , E.E. (1970), Experimental detemunatlon of the shape factors and the bearing and capacity factors of sand, Geotechnique, 20, N.4,387-411.
4. Hansen, J.B (1970), A Rivised and Extended Fomula for Bearing Capadty, Danish Geotechnical Institute Bui, lto.2S, Copenhagen.
5. Meyerhof, G.G.(19S6), Penetration test and bearing capacity of cohesionless soils, American