SIMULATION OF THE UNDRAINED SHEAR BEHAVIOR OF INDUCED CEMENTED CLAY WITH A CEMENTED SOIL MODEL

Transcription

1 PSU-UNS Intrnational Confrnc on Enginring and Enironmnt - ICEE-7, Phukt May1-11, 7 Princ of Songkla Unirity, Faculty of Enginring Hat Yai, Songkhla, Thailand 9112 SIMULATION OF THE UNDRAINED SHEAR BEHAVIOR OF INDUCED CEMENTED CLAY WITH A CEMENTED SOIL MODEL Jirayoot Subook 1, Sukun Horibuluk 2, and Martin D. Liu 3 1, 2 School of Ciil Enginring and Contruction Tchnology Rarch Unit (CTRU Suranar Unirity of Tchnology, Nakhon Ratchaima, Thailand 3 Dartmnt of Ciil Enginring, Th Unirity of Nw South Wal, Autralia Author to corrondnc hould b addrd ia mail: jirayoot@yahoo.com Abtract: A Cmntd Soil (CS modl i introducd in thi ar a an aroriat contituti modl for oling ractical gotchnical roblm. It i formulatd bad on th modifid ffcti tr conct [1 and 2]. Th ffct of cmntation and th brakdown of cmntation on oil bhaior ar incororatd. Th yild urfac i llitical in ha. Th conct of ub-yilding i introducd in th CS modl for modling th latic dformation for loading inid th yild urfac. Th aramtr in thi modl can b imly dtrmind from conntional triaxial tt on cmntd aml. In thi ar, th rformanc of th modl i rifid by comarion of modl imulation and xrimntal data for tt at ariou tr ll and on Bangkok clay aml with diffrnt dgr of cmntation. Ky Word: Bangkok clay, Cmntation, Cmntd clay, Cmntd Soil modl, Modifid ffcti tr 1. INTRODUCTION Soil tructur (fabric and cmntation i a rim factor controlling th nginring bhaior of clay. Liu and Cartr [3] and Cartr and Liu [4] ha introducd it influnc into th Modifid Cam Clay (MCC modl [5]. Th tructurd modl wa dignatd a Structurd Cam Clay (SCC modl. Th modl i uitabl for naturally cmntd clay in which cohion i inignificant. It ha bn obrd that for cmntd clay, articularly tho with inducd cmntation, th inhrnt cohion lay a ignificant art on oil bhaior [6, 7 and 8]. Rcntly, Subook t al. [1] ha introducd a nw modl for cmntd clay rfrrd to a Cmntd Soil (CS modl. A aramtric tudy of th modl aramtr wa alo illutratd in thir tudy. In thi ar, th fatur of th CS modl i ummarizd and rifid by comarion of th modl imulation and xrimntal data (diator tr ru har train, ffcti tr ath and dlomnt of xc or watr rur. Th xrimntal data ar of cmntd Bangkok clay from Uddin [1]. 2. GENERAL DESCRIPTION OF CEMENTED SOIL MODEL Th CS modl for cmntd clay i introducd hr with th mhai on modling th ffct of cmntation on oil bhaior. Th aim of th modl i to roid a contituti modl uitabl for th olution of boundary alu roblm ncountrd in gotchnical nginring ractic, i.., a ractical tool. It i thrfor ncary to k th modl rlatily iml and with th modl aramtr connintly and unambiguouly dtrminabl from conntional tt. In thi modl, th tr and train aramtr ar th am a tho commonly adotd in oil mchanic. Bad on th modifid ffcti tr conct [1 and 2], th tr ratio i modifid a q η = (1 A modification on th tr aramtr, ffcti man tr, i rood a follow: = + b (2 whr i th xlicit man ffcti tr, ' i th conntional man ffcti tr and ' b i th additional man ffcti tr du to cmntation bonding Matrial idalization In th CS modl, oil i idalizd a an latic and irgin yilding matrial, a illutratd in Fig. 1.

2 IC CS q M 1 Δ RCL CSL yi, Δ i ln Cmntd oil: = +Δ (a Comrion bhaior of cmntd oil Loading Surfac M c c c M M ( CSL yi, Cmntd Yild Surfac (b Cmntd yild and Loading urfac Fig. 1. Matrial idalization for th CS modl In th modl, th comrion bhaior of cmntd clay i dcribd by uing that of th rfrnc comrion lin (RCL a a rfrnc (Fig 1a. Th ymbol, rrnt th oid ratio for a cmntd clay and i th oid ratio in th rfrnc comrion lin at th am ffcti tr. y,i i th man ffcti tr at which irgin yilding of th cmntd clay bgin. Δ, th additional oid ratio, i th diffrnc in oid ratio btwn cmntd and rfrnc tat at th am tr tat. Hnc, th irgin comrion bhaior of a cmntd clay can b xrd by th following quation, yi, = +Δi b (3 whr b i a aramtr quantifying th rat of dtructuring and i rfrrd to hr a th dtructuring indx. Δ i i th alu of th additional oid ratio at th tart of irgin yilding (' = ' y,i (Figur 1a. Thi quation aum that th additional oid ratio qual to zro whn th man ffcti tr rach infinity. To modl latic dformation for loading inid th yild urfac, th two-urfac thory wa adotd [1]. Th loading urfac i includd (Fig. 1b, and th bhaior of cmntd clay i alo diidd into ubyilding bhaior and irgin yilding bhaior by it two-yild urfac, which i dndnt on cmntation a wll a tr hitory. Hnc, th yild urfac i dfind by it currnt tr tat, oid ratio, and cmntation. Th yild urfac in q- ac i aumd to b llitical (aumd a MCC modl [5]. i th iz of th yild urfac, which i ffctily hiftd to th lft along th o axi by /M. Th lo of th critical tat lin of cmntd oil i aumd to b th am a that of th failur lin, M a hown in Fig. 1a Yild Surfac and Loading Surfac In ordr to dcrib accuratly th latic dformation of oil within th faibl conntional tting mthod, quation for rrnting th yild urfac and th loading urfac for thi modl wr rood by Subook t al. [1]. Th cmntd yild urfac for dry and wt id of failur nlo i gin by th yild function f, whr (( ( ( + + = (4 2 2 f : q M q / M q / M Th mathmatical form for th ub-yild urfac i th am a th cmntd yild urfac. Th iz of loading urfac in quation (4 can b dfind a ' c Elatic dformation For tr xcurion, dformation can b diidd into latic dformation and latic dformation. Th latic dformation of a cmntd clay i dcribd by Hook law, i.., ( ν 31 2 = d (5 E 21 ( + ν = dq (6 3E Volumtric Dformation for Cmntd Clay A fundamntal aumtion for th formulation of th contituti modl i that th hardning and dtructuring of cmntd clay ar dndnt on th latic dformation, bad on which th latic dformation i drid. Thn, th latic har dformation i obtaind ia th rood flow rul Volumtric Dformation for Sub-Yilding Th loading urfac includd in th CS modl i to xr th ub-yilding bhaior. Thi bhaior may occur for a tr chang which atifi th condition, [' c < ' y,i ] or [' c = ' y,i and d' c < ]. Th latic olumtric train incrmnt during ubyilding for cmntd oil i xrd in th following th quation rood by Subook t al. [1]: M η ci, = M ci, d + bδ d ( λ κ ( ' / ( 1+ ( 1+ ωα c c c c whr M c,i i th initial lo q/ at /2, aramtr α rrnt th kinmatic hardning ffct to cmntation. Gnrally α tak a alu btwn infinity and, with α = infinity corronding to urly latic dformation, and α = corronding to irgin yilding. A iml calar xrion for α i uggtd a, (7

3 2 c c if d c c, hi α = 2 c if d c < chi, (8 Th following quation wa thrfor rood a a flow rul for cmntd clay [1], = M 2 2 c 2ηβ η + 1 (13 in which c,hi i th iz of th loading urfac whr unloading or rloading occur. Th momnt th currnt tr tat rach th yild urfac and d c >, irgin yilding commnc Volumtric Dformation for Virgin Yilding For tr tat on th yild urfac and with d >, irgin yilding occur. Th latic olumtric train incrmnt for th CS modl i drid from th aumtion that both hardning and dtructuring of clay ar dndnt on olumtric dformation, and gin a, d d d ( b ε = λ κ + Δ + κ ( 1+ ( 1+ Th lat trm on th right hand id of Equation (9, which i dndnt on th currnt man tr, i aociatd with latic dformation. Thu, th latic olumtric train can b obtaind by ignoring latic dformation art in Equation (9 a hown in quation (1 d = ( λ κ + bδ ( 1+ (9 ( Volumtric Dformation for Softning Bhaior Thi modl aum that whn th tr tat rach th failur tat, th cmntd clay undrgo cruhing of th clay-cmnt tructur and ntually rach th critical tat ( / =. It i aumd that th rduction in q during th cruhing of th clay-cmnt tructur i dcribd by th following quation, ( 3 3 dq = q / M d (11 In thi ca, a gnral tr and train rlationhi for thi roc can b obtaind a, dq = M d dq κ d = ( Flow rul Th cmntation alo ha influnc on th flow rul. It i obrd that a cmntd clay with oiti Δ gnrally ha a lowr alu for th train incrmnt ratio / than th corronding rcontitutd oil at th am irgin yilding tr tat. Moror, th train incrmnt ratio / at failur tat i not infinity. whr M c i th lo q/ at /2, which chang with th iz of th yild urfac, i th alu of th iz of th quialnt yild urfac. Th quialnt yild urfac i dfind a th yild urfac for th cmntd clay in a critical tat (without additional oid ratio at th am tr tat. Bad on th rfrnc comrion quation, th following quation for can b found IC x λ κ = κ λ κ (14 whr IC i th oid ratio of rfrnc comrion lin at unit man ffcti tr. Th modifir hould not b ngati othrwi th latic train incrmnt ctor will alway b dirctd inid th yild urfac. Whn th tr tat i at critical tat, M c = η and =, hnc =. 3. SIMULATING THE UNDRAINED SHEAR BEHAVIOR OF INDUCED CEMENTED CLAY Th undraind tt rult rortd by Uddin [1] ar conidrd for rifying th rood modl. Th ba clay i Bangkok clay, collctd from a it locatd at northrn art of th AIT camu rmi, Bangkok, Thailand. Th clay i highly latic with natural watr contnt in a rang of rcnt. Th liquid and latic limit ar in th ordr of 13 and 47 rcnt. Th aarnt r-conolidation rur i 7 kpa. Th ffcti trngth aramtr in comrion ar c' = and φ' = Th oil wa thoroughly mixd with ordinary Portland cmnt (Ty I at diffrnt cmnt contnt of 5%, 15% by wight. Iotroically conolidatd undraind triaxial comrion (CIUC tt wr carrid out on aml aftr 4 wk of curing. Th ffcti confining rur, σ' c, wr from 1 to kpa. Th modl aramtr adotd for th analyi ar litd in Tabl. 1. Valu of aramtr IC, λ, b, c, Δ i and y,i wr dtrmind from th rult of iotroic comrion tt on cmntd aml. Valu of and M wr dtrmind from th (q, ' lot for inducd cmntd clay. Th alu for aramtr ω and β wr dtrmind by imulating th latic har dformation. Comarion of imulatd and maurd tt rult for ariou cmnt contnt ar hown in Figur 2 to 5. It i found that th modl can catur wll th undraind har ron for both r- and ot-yild tat.

4 Tabl 1 Modl aramtr for cmntd Bangkok clay y,i (kpa Δ i b ν ω (kpa Μ λ κ c β Diator tr, q (kpa Bangkok clay with C = 15% σ' c = kpa σ' c = 5 kpa Diator tr, q (kpa Bangkok Clay C = 15%, ' y,i = 731 kpa 1 3 Man ffcti tr, ' (kpa Fig. 2. Simulatd and maurd undraind tr ath of 15% cmnt aml at r-yild tat Diator tr, q (kpa C = 5% ' y,i = 11 kpa 8 Man ffcti tr, ' (kpa Fig. 3. Simulatd and maurd undraind tr ath of 5% cmnt aml at ot-yild tat Exc or rur, Δu (kpa σ' c = kpa Shar train, ε (% imulatd maurd σ' c = 5 kpa Shar train, ε (% Fig. 4. Simulatd and maurd (q-δu-ε rlationhi of 15% cmnt aml at r-yild tat Diator tr, q (kpa Exc or rur, Δu (kpa 5 3 Bangkok clay with C = 5% σ' c = kpa Shar train, ε (% imulatd σ' c = kpa σ' c = kpa maurd σ' c = kpa σ' c = kpa σ' c = kpa Shar train, ε (% Fig. 5. Simulatd and maurd (q-δu-ε rlationhi of 5% cmnt aml at ot-yild tat

5 4. CONCLUSION Thi ar rnt a tudy on th dlomnt and alication of a ractical modl for dcribing th undraind bhaior of inducd cmntd clay. Th concluion can b drawn a follow. 1. Bad on th modifid ffcti tr and th tat boundary urfac conct, th Cmntd Soil (CS modl wa dlod. Th modl can imulat wll th tr-train rlationhi, xc or rur dlomnt, and undraind tr ath of inducd cmntd clay both for r- and ot-yild tat. 2. Th ub-yilding conct includd in CS can imulat wll th latic dformation inid th yild urfac. 3. Th modl aramtr can imly b obtaind from th rult of conntional triaxial comrion. Thu, th CS modl can b conidrd a a aluabl tool for gotchnical ractitionr. 5. ACKNOWLEDGEMENT Th firt and cond author acknowldg th financial uort roidd to thm by Suranar Unirity of Tchnology. 6. REFERENCES [1] J. Subook, S. Horibuluk, and M.D. Liu, A Cmntd Soil modl for cmntd clay. Procding of th 12 th National Conntion Thailand on Ciil Enginring (NCCE, Thailand, 7. [2]S. Horibuluk, J. Subook, M.D. Liu, and J.P. Cartr, Simulation of undraind har bhaiour of cmntd clay with th Modifid Structurd Cam Clay modl. Procding of th 6 th Intrnational Symoium on Soil/Ground Imromnt and Goynthtic (ISGIS, Bangkok, Thailand, 6, [3] M.D. Liu and J.P. Cartr. A tructurd Cam Clay modl. Canadian Gotchnical Journal, 2, No. 39, [4] J.P. Cartr and M.D. Liu. Riw of th Structurd Cam Clay modl. Initd ar, Soil contituti modl: aluation, lction, and calibration, ASCE, Gotchnical cial ublication, 5, Vol. 128, [5] K.H. Roco, J.B. Burland. On th gnralizd tr-train bhaior of wt clay, Enginring laticity, Editd by J. Hyman and F.A. Lcki, Cambridg Unirity Pr, 1968, [6] S. Horibuluk, N. Miura and D.T. Brgado, Undraind har bhaior of cmnt admixd clay at high watr contnt. Journal of Gotchnical and Gonironmntal Enginring, ASCE, 4, Vol. 13, No. 1, [7] A.E.Z. Wia, C.C. Ladd, and T.W. Lamb, Effcti tr trngth aramtr of tabilizd oil, Procding of 6 th Intrnational Confrnc on Soil Mchanic and Foundation Enginring, 1965, [8] G.W. Clough, N. Sitar, R.C. Bachu, and N.S. Rad, Cmntd and undr tatic loading, Journal of Gotchnical Enginring Diiion, ASCE, Vol. 17(GT6, 1981, [9] K. Kaama, H. Ochiai, and N. Yaufuku, On th tr-train bhaiour of lightly cmntd clay bad on an xtndd critical tat conct, Soil and Foundation, Vol.4, No.5,, [1] Md. Kamal Uddin, Strngth and dformation charactritic of cmnt-tratd Bangkok clay. Ph.D dirtation, 199, AIT, Bangkok.