THERMAL CONSOLIDATION OF SOFT BANGKOK CLAY

THERMAL CONSOLIDATION OF SOFT BANGKOK CLAY Aul-Ng, H. M. 1, Brgdo, D. T. 2, Sorlump, S. 3, nd Rujivipt P. 4 ABSTRACT: Undrstnding th thrmo-mhnil hvior of sturtd fin grind soils hs om vry importnt topi whnvr th gothnil prolms involv thrml ffts. Prvious rsrh works in litrtur show tht y sujting th sturtd fin-grind soils to tmprtur lss thn wtr oiling point volumtri nd shr strngth hngs r indud. Th thrmlly indud hngs hv n ttriutd to th physio-hmil hng t th mirosopi lvl. Th im of this rsrh is to study th thrmo-mhnil hvior of nturl soft Bngkok ly, with tmprtur up to 9 o C. Intnsiv lortory tsts using modifid odomtr pprtus wr ondutd to invstigt this hvior. Th tsting progrm ws dirtd to study th fft of ht on th thrmlly indud volum hng t diffrnt tmprtur nd strss onditions, th thrml volution of th pronsolidtion prssur, th indud ovronsolidtion hvior ftr hting/ooling yl, nd th fft of tmprtur on th hydruli ondutivity. Th xprimnts rrid out on soft Bngkok ly providd som dditionl usful dt on th thrmo-mhnil hvior of th soft dposits. Th rsults of this rsrh work hv n omprd with thos in litrtur with diffrnt ly typs to gnrliz th thrmo-mhnil hvior of th sturtd lys. Ky Words: Thrmo-mhnis, ly, tmprtur, volum hng. INTRODUCTION Th lr undrstnding for th fft of tmprtur on th soil hvior oms mndtory for mny nginring pplitions suh s dsign of nulr wst disposl filitis (Dvis nd Bnrj 198), urid ltril ls (Adl-Hdi nd Mithll 1981), oil nd gs pip lins (Slgl nd Dvis 1977), nd ground ht nrgy storg (Moritz 1995). Ths pplitions hv ld to inrsing onsidrtions of th tmprtur ffts on th nginring proprtis of soils nd hv md th thrmomhnil hvior of soils s on of th mjor issus in modrn soil mhnis. Intrst in this topi dts k from th sixtis, whn th first onfrn onrning th fft of tmprtur nd ht on nginring hvior of soils ws hld in Wshington D.C., U.S.A. in 1969. Th tmprtur rngs usd in th rly rsrh works wr limitd to th rng of 1 to 5 o C. This limittion ws undrstood, us th mjor onrn t tht tim ws to study th fft of tmprtur hng on th volumtri nd strngth prmtrs of th soil spimn during smpling nd trnsporttion to th lortory. Howvr, whn th rsrh studis wr dirtd to dsign sf rdiotiv disposl in ly formtions, undrstnding of th thrmomhnil hvior t tmprturs up to 1 o C om importnt. Prvious rsrh works in litrtur show tht sujting th sturtd fin-grind soils to tmprtur lss thn wtr oiling point indus volumtri nd shr strngth hngs. In th sn of vidn of hng in minrlogy upon hting th sturtd fin-grind soils up to 9 o C (Grhm t l. 21), ll th prvious rsrh works hv ttriutd th thrmo-mhnil hvior to th hngs in th thrmlly indud physio-hmil fors twn th ly prtils upon hting. Sridhrn nd Vnktpp Ro (1973), Morgnstrn nd Blsurmonin (198), nd Mithll (1993) found tht hngs in por-fluid vln, onntrtion, prmittivity, nd tmprtur hv signifint fft on th physio-hmil fors twn th ly prtils whih ontrol th mhnil hvior of th sturtd fingrind soil Thrfor, it is vidnt tht hngs in th por-fluid tmprtur my ltr th shr strngth hvior nd indu volumtri strin. Lloui (21) hs prsntd rviw of th rsrh work on thrmo-mhnil hvior of th sturtd fingrind soils s summrizd low: 1) Th thrmlly indud volumtri hngs dpnd on th strss history ondition (Bldi t l. 1988; Towht t l. 1993). It is irrvrsil ontrtion for th normlly onsolidtd lys whil it oms rvrsil xpnsion for th highly ovronsolidtd lys. 2) Th normlly onsolidtd lys show highr pronsolidtion prssur upon rloding ftr sujting to hting ooling yl (Towht t l. 1993; Roint t l. 1996; Burghignoli t l. 2). 3) Diffrnt ly typs show rdution of th lsti domin t lvtd tmprtur (Ckrv t l. 22). 4) Th hydruli prmility of th lys inrss with tmprtur (Towht t l. 1993; Dlg t l. 2). 1 Dotorl Cndidt, Shool of Civil Enginring, Asin Institut of Thnology, P.O. Box 4, Khlong Lung, Pthumthni, Thilnd, 1212 (Phon: 662-524-5512; Fx: 662-524-65; Emil: St299@it..th). 2 Profssor of Gothnil Enginring, Shool of Civil Enginring, Asin Institut of Thnology, P.O. Box 4, Khlong Lung, Pthumthni, Thilnd, 1212 (Phon: 662-524-5512; Fx: 662-524-65; Emil: rgdo@it..th). 3 Lturr, Dprtmnt of Civil Enginring, Kstsrt Univrsity, Bngkok, Thilnd. 4 M. Eng. Grdut, Shool of Civil Enginring, Asin Institut of Thnology, P.O. Box 4, Khlong Lung, Pthumthni, Thilnd, 1212. 1

5) Th fft of tmprtur on th shr strngth dpnds on th dring ondition upon hting nd strss history (Grhm t l. 21). Whil most of th rlir rsrh works wr dvotd to study th thrmo-mhnil hvior of stiff sturtd lys. Only fw rsrh works wr dvotd to study th thrmo-mhnil hvior of nturl soft dposits. Th im of this rsrh is to study th thrmo-mhnil hvior of nturl soft Bngkok ly undr tmprturs up to 9 o C. Intnsiv lortory tst progrm using modifid odomtr pprtus ws ondutd. Th proposd xprimntl progrm ovrd th fft of tmprtur on th thrmlly indud volum hng t diffrnt strss ondition, th indud ovronsolidtion hvior ftr hting/ooling yl for normlly onsolidtd lys t diffrnt strss nd tmprtur ondition, volution of th pronsolidtion prssur with tmprtur, nd th fft of tmprtur on th hydruli ondutivity. Th following stions prsnt th mtril nd mthods of tsting long with th tsting rsults nd disussions. MATERIAL Th nturl soft ly usd in this study ws xtrtd from dpth of 3. to 4. m of th soft ly lyr in th mpus of Asin Institut of Thnology (AIT) whih is within th Cntrl Plin of Thilnd. Th Cntrl Plin of Thilnd ontins th dlti-mrin dposit of soft ly lyr widly known s soft Bngkok ly. Tl 1 shows th proprtis of soft Bngkok ly. Th minrlogil omposition of Bngkok Cly ws invstigtd y Ohtsuo t l. (2) using XRD tsts. Th rsults show tht Bngkok Cly possssd smtit, kolinit nd mi. Th mjor ly minrl is group of smtit (Montmorillonit nd Illit) with rng of 54 to 71%, followd y Kolinit (28-36%) nd Mi. TEST APPARATUS Figur 1 shows modifid odomtr tht n tst soil spimn t lvtd tmprtur up to 9 o C ws usd in this study. Th modifid odomtr onsists of onvntionl odomtr pprtus, ring htr of 6 W pity, typ K thrmooupl, wtr tnk, nd thrmoontrollr unit with ury.1 o C. Th ring htr ws tthd to th outr ring of th onvntionl odomtr pprtus. Hting of th soil spimn ws hivd indirtly y hting th wtr in th nnulr sp twn th outr ring of odomtr nd th spimn ring. Using th ring htr, th homognity of wtr tmprtur round th soil spimn during th tst priod ws insurd. Th wtr lost y vportion from th odomtr unit ws simultnously ompnstd y hot wtr supply t th tst tmprtur. Th ring htr ws onntd to th thrmoontrollr unit to kp th tmprtur onstnt within th rng of ±.1 o C. Tl 1 Proprtis of soft Bngkok ly Proprtis Chrtristis vlu Liquid limit, LL, (%) 13 Plstiity indx, PI, (%) 6 Wtr ontnt, w (%) 9-95 Liquidity indx, LI.62 Grin siz distriution Cly (%) 69 Silt (%) 28 Snd (%) 3 Totl unit wight, γ t, (kn/m 3 ) 14.3 Dry unit wight, γ d, (kn/m 3 ) 7.73 Spifi grvity 2.68 Initil void rtio, 2.4 Color Drk gry Ativity.87 Snsitivity 7.4 Tmprtur msurmnts nd th fdk signl for th thrmo-ontrollr unit wr otind y thrmooupl pld in th odomtr nnulus sp in ordr to void spimn disturn during th thrmooupl intrusion into th spimn. Th thrml dformtion of th tst pprtus wr lirtd rfully. Th vrtil dformtion of th odomtr lmnts wr tstd y onduting numr of tsts, without spimn, t diffrnt tmprturs nd strss lvls. Th rdil dformtion of th odomtr ring ws msurd dirtly ftr sujting it for long tim in ovn t th tstd tmprtur. Th msurmnts show tht th fft of th rdil dformtion is insignifint nd n ngltd. Similr onlusion ws rportd y Towht t l. (1993). Th diffrn twn th spimn tmprtur nd th tmprtur of wtr in th nnulr sp ws lso lirtd y msuring simultnously th tmprtur of thrmooupl mddd in th spimn ntr nd nothr on in th nnulr sp. Hot wtr Eltri htr Dt quisition Dil gg Loding m Soil spimn Thrmo-ontrollr unit Fig. 1 Shmti drwing for th modifid odomtr pprtus Thrmo-oupl 2

EXPERIMENTAL PROGRAM To study th thrmo-mhnil hvior of soft Bngkok ly two typs of tmprtur-loding pths wr doptd. Th first pth, lld thrml loding pth, involvd hnging th soil tmprtur t onstnt strss ondition (ithr, t normlly onsolidtd stt or ovronsolidtd stt) to otin th soil rspons s funtion of tmprtur (Fig. 2). This pth ws pplid to invstigt th thrmlly indud volum hng t diffrnt tmprturs nd strss onditions. To invstigt th fft of th strss lvl on th thrmlly indud volum hng thr groups of spimns (h group onsists of six spimns) wr tstd. Th spimns of h group wr onsolidtd undr diffrnt strss lvls grtr thn its nturl pronsolidtion prssur. Bsd on th rsults of th inrmntl mhnil onsolidtion tst th nturl pronsolidtion prssur ws found to 7 kp. Th spimns in th thr groups wr onsolidtd undr 1, 2, 3 kp rsptivly. To invstigt th fft of th strss history on th thrmlly indud volum hng thr spimn of h group wr unlodd to diffrnt ovronsolidtion rtios (2, 4, nd 8). Thn ovronsolidtd spimn in h group ws sujtd to hting/ooling yl (25-9-25 o C) whil th thr normlly onsolidtd spimns wr lso sujtd to diffrnt hting/ooling yl (25-5-25 o C, 25-7-25 o C, nd 25-9-25 o C). Th mounts of sttlmnts wr osrvd during th hting nd ooling phss. Th irrvrsil thrmlly indud volum hng n lultd t th nd of th ooling phs. At th nd of th drind hting/ooling phs, th normlly onsolidtd spimns wr sujtd to inrmntl mhnil rloding t mint tmprtur to otin th hng in th lsti rng ftr sujting it to diffrnt vlus of thrml lod yl. Th sond pth, lld isothrml mhnil loding pth, involvd pplying mhnil lod to ovronsolidtd ly spimn t lvtd tmprtur (mor thn th mint tmprtur) to invstigt th thrml volution of th soil onsolidtion urv (Fig.3). This study rings out th fft of tmprtur on th siz of th lsti domin. Furthr, th fft of tmprtur on th onsolidtion rt upon loding n utilizd to stimt indirtly th fft of tmprtur on th offiint of hydruli ondutivity. To invstigt th fft of th initil pronsolidtion prssur (t mint tmprtur) on th volution of th pronsolidtion prssur undr lvtd tmprturs two groups of spimn wr tstd undr this pth with h group onsistd of four spimns. Th first group of spimns ws onsolidtd undr 1 kp whil th sond group of spimns ws onsolidtd undr 2 kp. Both group spimns wr sujtd to mhnil unloding until OCR=12 t mint tmprtur ftr th onsolidtion stg. Thr spimns of h group wr sujtd to inrmntl ht up to diffrnt tmprtur lvls (5, 7, 9 o C) whil th tmprtur of th lttr group of spimns ws kpt t th mint tmprtur (25 o C). At th nd of th hting stg, th four spimns wr sujtd to mhnil inrmntl rloding. Th tsts wr trmintd whn th spimns wr strining ontinuously inditing th yilding mod nd th vill points in th fftiv strss-strin sps r nough to dtrmin th slop of th omprssion hrdning lin. DISCUSSIONS OF THE TEST RESULTS Thrmlly Indud Volum Chng Th thrmlly indud volum hng ftr yls of drind hting/ooling t diffrnt strss history ws studid y mny rsrhrs (.g. Plum nd Esrig 1969; Dmrs nd Chrls 1981; Bldi t l. 1988; Towht t l. 1993; Roint t l. 1996; Burghignoli t l. 2; Lloui nd Ckrv 23). Tmprtur ) Normlly onsolidtd spimn Tmprtur Void rtio T 1 T Void rtio T 1 T p p OCR OCR ) Ovr-onsolidtd spimn Fig. 2 Thrml loding pth d P d P d, p OCR d p OCR f Efftiv strss f Efftiv strss Efftiv strss Efftiv strss 3

Tmprtur Void rtio T 1 T d d P P Efftiv strss Efftiv strss tht ontrols th thrmo-mhnil hvior. Th prntg of fins n lso fft th soil hvior t onstnt soil plstiity indx. Towht t l. (1993) studid th fft of th strss lvl on th thrmlly indud void rtio hng of th normlly onsolidtd lys. It ws found tht whn th normlly onsolidtd lys r sujtd to drind hting th mount of void rtio hng is indpndnt on th strss lvl (pronsolidtion prssur). Th xprimntl progrm of th urrnt rsrh work, invstigtd th fft of th pronsolidtion strss on th void rtio hng for th normlly nd th ovronsolidtd ly spimns. Figur 7 shows th thrml void rtio hng on ly spimns onsolidtd undr diffrnt strss vlus (1, 2, 3 kp) nd unlodd to diffrnt strss historis (OCR = 1, 2, 4, 8) for sujting to tmprtur hng T = 65 o C. Th rsults indit tht th void rtio hngs r indpndnt on th initil pronsolidtion prssurs. Fig. 3 Isothrml mhnil loding pth It ws dmonstrtd tht th normlly onsolidtd lys ontrt irrvrsily nd non-linrly upon hting. Howvr, whn ovronsolidtd lys wr htd, th mgnitud of volum ontrtion ws smllr thn tht of normlly onsolidtd smpls. In ddition, th highly ovronsolidtd ly xhiitd rvrsil volum xpnsion whn htd. Th soft Bngkok ly shows similr thrmlly indud volum hng hvior undr hting up to 9 o C s shown in Fig. 4. Th normlly onsolidtd spimns show irrvrsil ontrtion whil for th highly ovronsolidtd spimn (OCR=8) th thrml hvior oms rvrsil with initil xpnsion. Figur 5 shows tht th thrmlly indud volumtri strin t diffrnt tmprtur lvl dpnds on th OCR vlus. At rtin tmprtur lvl, s th soil ondition hngd from th normlly onsolidtd stt to th ovronsolidtd stt th ontrtion volumtri strin drss nd oms xpnsion yond rtin OCR vlus. Roint t l (1996) ttriutd th thrmlly indud volum hng hvior to th physio-hmil intrtions whih r strss indpndnt ut dpndnt ssntilly on th ly ltti onstitution, th hmil ntur of th intrstitil fluid, nd intrlyr distn. Th soil plstiity indx n onsidrd s n indition for th intnsity of th physio-hmil intrtions upon hting nd my fft quntittivly th thrmlly indud volumtri strin. Dmrs nd Chrls (1982) msurd th thrmlly indud volum hng for six diffrnt nturl mrin lys nd onludd tht th thrmlly indud volum hng inrss s th soil plstiity inrss. Figur 6 shows th thrmlly indud volum hng rsults vrsus th soil plstiity indx of diffrnt typs of normlly onsolidtd lys xisting in th litrtur tht wr sujtd to tmprtur hng of T = 65 to 7 o C. A rltion twn th thrmlly indud volumtri strin nd th soil plstiity indx ould ddud. Howvr, it is thought tht th soil plstiity indx is not th only ftor Tmprtur [ o C] 1 8 6 4 2 -.1.1.2.3.4.5.6 ε v OCR=1 OCR=2 OCR=4 OCR=8 Fig. 4 Soft Bngkok ly thrml volumtri strin during drind hting/ooling yl t diffrnt OCR vlus (pronsolidtion prssur = 2 kp) ε v.8.6.4.2. -.2 5 o C 7 o C 9 o C 2 4 6 8 1 OCR Fig. 5 Efft of OCR vlus on th thrmlly indud volumtri strin of soft Bngkok ly t diffrnt tmprtur lvl (pronsolidtion prssur = 1 kp) 4

εv.6.4.2 Trnd lin for tst rsults Moritz (1995) (LL= 65%) Soft Bngkok ly (LL=13%) Eriksson (1989) (LL=11%) Ckrv t l. (22) (LL=45%) 2 4 6 8 Plstiity indx [%] MC ly (Towht t l. 1993) Boom ly (Sultn t l. 22) Soft Bngkok ly Illiti shl (Grhm t l. 21) Boom ly (Bldi t l. 1991) MC ly (Lloui nd Ckrv 23) Fig. 6 Efft of soil plstiity indx on th thrmlly indu volumtri strin for diffrnt normlly onsolidtd lys ( T= 65 o C).2.15.1.5. -.5 1 2 3 4 Pronsolidtion prssur [kp] OCR=1 OCR=2 OCR=4 OCR= 8 Fig. 7 Efft of th pronsolidtion prssur on th soft Bngkok ly thrmlly indu void rtio hng t diffrnt OCR vlus ( T = 65 o C, T o = 25 o C) Evolution of th Pronsolidtion Prssur with Tmprtur Mny xprimntl rsrh works (.g. Tidförs nd Sällfors 1989; Eriksson 1989; Moritz 1995; Boudli t l. 1994, Lrouil, nd Mrqus 1996; Lrouil 1997; Sultn t l. 22; Ckrv t l. 22) hv n rrid out to study th fft of tmprtur ris on th onsolidtion hvior for diffrnt typs of soils. It ws found tht s th soil tmprtur inrss th pronsolidtion prssur drss. Figur 8 shows th volution of th pronsolidtion prssur normlizd y th pronsolidtion prssur t T= 2 o C of diffrnt soil typs in litrtur. Th hviour of soft Bngkok ly shows similr trnd. Figur 9 shows th thrml volution of pronsolidtion prssur of soft Bngkok ly t two diffrnt pronsolidtion prssurs (1, nd 2 kp). Boudli t l. (1994) Moritz (1995) Dpx (1975) Mrqus (1996) Cmpnll nd Mithll (1968) Akgi nd Komiy (1995) Tidfors nd Sllfors (1989) Soft Bngkok ly Eriksson (1989) Ckrv t l. (22) Fig. 8 Vrition of th normlizd pronsolidtion prssur with tmprtur (ftr Lrouil nd Mrqus, 1996). Th xprimntl rsults show th prntg of th hng in pronsolidtion prssur is strss lvl indpndnt. At T = 9 o C, th pronsolidtion prssur hng ws 24 nd 22 % for 1 nd 2 kp pronsolidtion prssurs, rsptivly. Diffrnt qutions hv n proposd in th litrtur to modl th thrml volution of th pronsolidtion prssur. Boudli t l. (1994) ssum linr rltion qution twn th pronsolidtion prssur nd tmprtur. Nonlinr rltion hs n proposd y Moritz (1995) nd Ckrv t l. (22) s givn in Eq.1 nd Eq. 2, rsptivly. σ σ σ σ ( ) ( T ) α T T = (1) T ( T) T ( ) = 1 γ log T T whr σ ( T ) nd σ ( T) r th pronsolidtion prssurs t room nd tstd tmprtur, rsptivly, α nd γ r th modl prmtrs whih dpnd on th soil typ. Soft Bngkok n fit wll with th two qutions t modl prmtr α=.16 for Eq. 1 nd γ=.42 for Eq. 2 s shown in Fig. 1,. Figur 11 shows th thrml volution of th pronsolidtion prssur normlizd y th pronsolidtion prssur t T= 2 o C prditd y Eq. 2 t diffrnt vlus of prmtr γ. Th prditd rsults indit tht th prmtr γ n xprss th intnsity of th pronsolidtion prssur hngs with tmprtur. As γ inrss, th hng in th pronsolidtion prssur du to tmprtur inrss. Ckrv t l. (22) proposd tht th modl prmtr γ ould rltd to th soil (2) 5

liquid limit vrying from 45 to 11% s shown in Fig. 12. Th trnd lins of th tst rsults in Fig. 8 show tht th soils tht hv highr liquid limit vlus dmonstrt highr thrml volution of th pronsolidtion prssur nd onsquntly orrsponding to high γ vlus. Soft Bngkok ly whih hs liquid limit out 13% shows tht th proposd rltionship n pplil (Fig. 12). Pronsolidtion prssur [kp] 25 2 15 1 5 1 kp 2 kp 2 4 6 8 1 Tmprtur [ o C] Fig. 9 Thrml volution of soft Bngkok ly pronsolidtion prssur Pronsolidtion prssur [kp] Pronsolidtion prssur [kp] 12 1 8 6 12 1 8 6 ) Moritz (1995) Eq. (1) α =.21 2 4 6 8 1 Tmprtur [ o C] ) Ckrv t l. (21) Eq. (2) γ=.42 2 4 6 8 1 Tmprtur [ o C] Fig. 1 Comprison twn msurd nd prditd soft Bngkok ly thrml volution of th pronsolidtion prssur σ' (T)/σ' (T=2 o C) 1.6 1.4 1.2 1.8.6.4 2 4 6 8 1 Tmprtur [ o C] γ =.1 γ =.2 γ =.4 γ =.8 Fig. 11 Thrml volution of pronsolidtion prssur t diffrnt vlus of γ γ.5.4.3.2.1 4 6 8 1 12 Liquid limit [%] Eriksson (1989) Tidfors nd Sllfors (1989) Moritz (1995) Ckrv t l. (22) Soft Bngkok ly Fig. 12 Evolution of th prmtr γ s funtion of soil liquid limit (ftr Ckrv t l. 22) Thrmlly Indud Ovronsolidtion Bhvior Towht t l. (1993), Roint t l. (1996), nd Burghignoli t l. (2) found tht whn th normlly onsolidtd lys r sujtd to drind hting/ooling yl, n inrmnt of strss is rquird to rh th yilding limit gin. Within this strss inrmnt th soil shows high omprssion stiffnss (lsti hvior) whn it is rlodd. This mns tht hting/ooling yl inrss th lsti rng nd indus ovronsolidtion hvior. Figur 13 shows th thrmlly indud ovronsolidtion hvior for soft Bngkok ly spimn onsolidtd undr 1 kp for sujting to drind hting nd ooling yl (25-9-25 o C). Th urrnt tsting progrm lso invstigtd th fft of tmprtur nd th initil mint pronsolidtion prssur on th mount of inrs in th lsti rng ftr sujting to drind hting/ooling yl. Normlly 6

onsolidtd ly spimns t diffrnt pronsolidtion prssurs (1, 2, 3 kp) wr sujtd to diffrnt tmprtur lvls (5, 7, 9 o C). Th xprimntl rsults r plottd in Fig 14. Th xprimntl rsults show tht s th tmprtur of th drind hting/ooling yl inrss, th pronsolidtion vlu inrss. Morovr, th rsults lso show tht t onstnt tmprtur lvl th prntg of pronsolidtion prssur hng ftr drind hting/ooling yl is indpndnt of strss lvl. Th hng in th pronsolidtion vlu upon sujting to drind hting/ooling yl (25-9-25 o C) for th ly spimn onsolidtd undr 1 kp, ws 35 kp whil for th ly spimn onsolidtd undr 2 nd 3 kp, it ws 75 nd 15 kp, rsptivly. Th tst rsults hv n normlizd s shown in Fig. 15 using th initil mint tmprtur pronsolidtion prssur, σ ( T ). Th inrs in th pronsolidtion prssur ftr sujting to drind hting/ooling yl ws rdud to singl linr rltionship twn th mximum yli tmprtur nd th normlizd pronsolidtion prssur. Efft of Tmprtur on th Hydruli Prmility Th fft of ht on th offiint of th hydruli ondutivity hs n invstigtd xprimntlly y mny rsrhrs. Som of thm (.g. Highi 1977 nd Towht t l. 1993) usd th indirt mthod whih mploys th msurmnts of th offiint of onsolidtion, v, nd th offiint of volum hng, m v, tht otind from isothrml onsolidtion tsts prformd t vrious tmprturs lvl. Othr invstigtors (.g. Morin nd Silv 1984 nd Dlg t l. 2) usd th dirt mthod, th onstnt hd mthod. All of th rsrhrs rportd tht th hydruli ondutivity of soil inrss with inrsing th tmprtur. Thr r thr ftors ffting th soil hydruli ondutivity. First, th proprtis of th fluid (soil liquid phs) whih inluds th visosity nd th unit wight of th fluid. Sond, proprtis of soil mtrix whih dsri th siz of flow hnnl twn soil prtils within th soil smpl. Third, th physio-hmil intrtions twn soil prtils nd th surrounding liquid whih fft lso th siz of th flow hnnl. Wtr n ound to th soil mtrix. Th dgr of inding vris from unoundd or fr wtr whih is t distn from th soil prtil surf nd n flow undr norml hydruli grdint, to strongly ound or dsord wtr, lld diffus doul lyr, whih is nr th soil prtil surf. Thrfor, th hng in hydruli ondutivity n ttriutd to ithr th hngs in diffus doul lyr thiknss, th soil mtrix s rsult of soil volum hngs, or th fluid proprtis. Morin nd Silv (1984), Mithll (1993) nd Dlg t l. (2) found tht th fft of tmprtur on th thiknss of th diffus doul lyr nd th soil mtrix is insignifint. Th fft of thrmlly indud volum hng on th soil mtrix is smll to rsponsil for th hydruli ondutivity hng t lvtd tmprtur (Houston nd Lin, 1987). Void rtio 2.5 2.3 2.1 1.9 1.7 1.5 25-9-25 o C 1 1 1 Vrtil fftiv prssur [kp] Fig. 13 Ovronsolidtion hvior of normlly onsolidtd soft Bngkok ly ftr hting/ooling yl Mximum yli tmprtur [ o C] 1 8 6 4 2 1 kp 2 kp 3 kp 1 2 3 4 5 Pronsolidtion prssur [kp] Fig. 14 Th hng in th pronsolidtion prssur of th normlly onsolidtd soft Bngkok ly t diffrnt strss lvl ftr hting/ooling yl t diffrnt tmprtur lvl Mximum yli tmprtur [ o C] 1 8 6 4 2 1 kp 2 kp 3 kp 1 1.1 1.2 1.3 1.4 OCR ftr hting/ooling yl Fig. 15 Th hng in th OCR vlu of th normlly onsolidtd soft Bngkok ly ftr hting/ooling t diffrnt tmprtur lvl On th othr hnd, th tmprtur hs dirt signifint fft on th physil proprtis of th soil liquid spilly th visosity. Thrfor, t rtin soil porosity th rtio twn th hydruli prmility t tstd tmprtur k (T) nd t mint tmprtur k (T o ) n stimtd using Kozny-Crmn qution s follows: 7

k(t) µ (To ) γw (T) = (3) k(t ) µ (T) γ (T ) o whr µ(t) nd µ(t o ) r th por wtr visosity t tst nd room tmprtur, rsptivly, nd γ w (T) nd γ w (T o ) r th por wtr unit wight t tst nd room tmprtur, rsptivly. Th thrml vrition of fr pur wtr visosity n stimtd ording to Hilll (198) s follows: µ(t) = -.46575 ln (T) +.239138 (4) whr T is th wtr tmprtur. Hn, Eqs. 3 nd 4 n usd to prdit th tmprtur fft on th hydruli ondutivity. Although, th mntiond disdvntgs y Tvns t l. (1983) nd Dlg t l. (2) for th dtrmintion of soil prmility using th indirt mthod, it n usd for omprison purpos twn th soil prmility t diffrnt tmprturs us of th nlltion of th rror sour. Bsd on dirt mthod xprimntl rsults, Dlg t l. (2) found tht t diffrnt tmprtur lvls th msurd offiint of volum hng vlus, m v, r 3 to 4 tims highr thn th lultd m v using th following qution: w o k= m v γ w v (5) Thrfor, it ws onludd tht th indirt prmility msurmnt from th onsolidtion tst yildd highr vlu. Howvr, th rror sour in th indirt mthod is tmprtur indpndnt. Th rsults of th iso-thrml odomtri xprimntl progrm t diffrnt tmprtur lvl hv n usd to dtrmin indirtly th hydruli prmility of soft Bngkok ly t diffrnt tmprtur. Figur 16 shows th inrs in th onsolidtion rt of soft Bngkok ly s th tst tmprtur inrss. Furthrmor, Fig. 17 shows th inrs in th msurd hydruli prmility of soft Bngkok ly normlizd y th mint tmprtur hydruli ondutivity vlu. Th prditd inrs in th hydruli prmilitis using Eq. 3 nd 4 hs n plottd lso in Fig. 17 for omprison purposs. Th xprimntl rsults show tht th inrs in prmility du to tmprtur inrs is los to th prditd vlus using Eqs.3 nd 4. Th osrvd dvition of th xprimntl rsults from th prditd vlus n ttriutd to th vrition of slt onntrtion in wtr whih signifintly modifis th rltionship twn visosity of wtr nd tmprtur (Burghignoli t l. 1995). CONCLUSIONS Th rsults of th xprimntl progrm rrid out on th soft Bngkok ly to invstigt th thrmo-mhnil hvior of th soft dposits n onludd in th following points: Sttlmnt [mm] 1 2 3 4.5 1 1.5 2 Squr root tim [minut] Inrmnt onsolidtion prssur = 16-32 kp Fig. 16 Consolidtion rt of normlly onsolidtd soft Bngkok ly t diffrnt tmprtur Prmility k/k t 25 o C 3.5 3. 2.5 2. 1.5 1..5. 25 7 9 Msurd Clultd 2 4 6 8 1 Tmprtur [oc] Fig. 17 Comprison twn th msurd nd th lultd vrition in th hydruli prmility with tmprtur 1) Thrmlly indud volum hng is strss history dpndnt nd strss lvl indpndnt. 2) Th thrml volution of th pronsolidtion prssur is nonlinr nd th prntg of th volution is strss lvl indpndnt. 3) Th normlly onsolidtd spimn shows ovronsolidtion hvior ftr sujting to drind hting/ooling yl. This hviour is funtion of th yli tmprtur. 4) Th hydruli prmility of sturtd soils inrss s th tst tmprtur inrss. This inrs is minly du to th orrsponding drs in th soil liquid visosity with tmprtur. 5) Th thrmo-mhnil hviour of sturtd fingrind soils, undr tmprtur lss thn th por liquid oiling point, hs n ttriutd to th physiohmil hngs, soil plstiity nd prntg of fins. Togthr, ths formntiond ftors n onsidrd s indition for th intnsity of th thrmlly indud hngs. 8

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