Development of In Situ Permeability Test Using Constant Discharge Method for Sandy Soils

Size: px

Start display at page:

Download "Development of In Situ Permeability Test Using Constant Discharge Method for Sandy Soils"

Baldric Hoover
6 years ago
Views:

1 Dvlopmnt of In Situ Prmability Tst Using Constant Discharg Mthod for Sandy Soils A. Rifa i, Y. Tashita, M. Komatsu Abstract Th post-rain puddls problm that occurs in th first yard of Prambanan Tmpl ar oftn disturbing visitor activity. A poodl layr and a drainag systm had vr built to avoid such a problm, but puddls still did not stop apparing aftr rain. Prmability paramtr nds to b dtrmind by using a simplr procdur to find xact mthod of solution. Th instrumnt modlling was proposd according to th dvlopmnt of fild prmability tsting instrumnt. This xprimnt usd a proposd Constant Discharg mthod. Constant Discharg mthod usd a tub pourd with constant watr flow from unsaturatd until saturatd soil condition. Volumtric watr contnt () wr monitord by soil moistur masurmnt dvic. Th rsults wr corrlations btwn and which wr drawn by numrical approach from Van Gnutchn modl. Paramtrs r optimum valu obtaind from th tst was at vry dry soil. Cofficint of prmability with a dnsity of 19.8 N/m 3 for unsaturatd conditions was in rang of 3 x 10-6 cm/sc (S r =68%) until 9.98 x 10-4 cm/sc (S r =82%). Th quipmnt and tsting procdur dvlopd in this rsarch was quit ffctiv, simpl and asy to b implmntd on dtrmining fild soil prmability cofficint valu of sandy soil. Using constant discharg mthod in proposd prmability tst, valu of prmability cofficint undr unsaturatd condition can b obtaind without stablish soil watr charactristic curv. Kywords Constant discharg mthod, in situ prmability tst, sandy soil, unsaturatd conditions. I. INTRODUCTION RAMBANAN Tmpl is a 9 th -cntury Hindu tmpl Pcompound in Cntral Java, Indonsia. Th tmpl compound, a UNESCO World Hritag Sit, is th largst Hindu tmpl sit in Indonsia and on of th biggst in th Southast Asia. To prsrv th hritag buildings and to nhanc th convninc of tourist activitis, rstoration and facilitis rparation around th tmpl ar rquird. Du to havy quipmnt activitis during rstoration priod aftr Yogyaarta arthqua in May, 2006, soil in tmpl yard has bcom dns and ponding ara occurrd during rainfall. Post-rain puddls which occurrd at crtain parts of Prambanan Tmpl yard is on of issus that nds to b solvd. This condition shows that th xisting drainag systm is not sufficint. Rainwatr infiltration procss abov th ground surfac can also b th caus of puddling. Infiltration is influncd by th charactristics of porous matrial or soil porosity. It initiats A. Rifa i is with th Dpartmnt of Civil and Environmntal Enginring, Univrsitas Gadjah Mada, Indonsia (corrsponding author to provid phon: ; fax: ; -mail: ahmad.rifai@ ugm.ac.id). Y. Tashita, M. Komatsu ar with th Graduat School of Environmntal and Lif Scinc, Oayama Univrsity, Oayama, , Japan (-mail: yujita@cc.oayama-u.ac.jp, momatsu@oayama-u.ac.jp). th altration of soil condition from unsaturatd to saturatd which causs th chang of soil prmability cofficint. This rsarch is focusd on dvlopmnt of mor simpl quipmnt for in situ tsting to masur prmability undr both saturatd and unsaturatd conditions. Th dtrmination of prmability cofficint valu was initiatd from unsaturatd soil condition to saturatd soil condition. II. LITERATURE REVIEW Rfrnc [4] proposs an xprimnt to masur unsaturatd hydraulic conductivity for sandy soil. Firstly, Gulph Prssur Infiltromtr (GPI) was usd to dtrmin th valu of hydraulic conductivity in saturatd conditions. Scondly, th unsaturatd hydraulic conductivity was masurd by Instantanous Profil Mthod during drainag tst. Th valus of volumtric watr contnt wr masurd using a PR1 Profil Prob typ (Dlta-T Dvics Ltd.) as an indicator of saturatd soil condition. Valus of hydraulic conductivity in unsaturatd condition wr obtaind from numrical modls as [5]. Th fild prmability tst was conductd for top soil in Piyungan wast disposal sit in Yogyaarta, Indonsia. Fig. 1 shows th rlationship btwn and volumtric watr contnt from unsaturatd until saturatd condition. This fild xprimntal mthod can b a good practical in-situ prmability tst bcaus of its simpl procdur. Howvr, this mthod is only limitd to th soil in disposal sit with homognous and uniform typ of soil. In addition, th usd tools wr also considrd too complx and difficult to obtain in Indonsia. Saturation indicator was only dtrmind whn th moistur snsor dvics wr usd. Thrfor, w nd a tool that is simpl, inxpnsiv, prcis, and abl to tst th soil with a highr dnsity. III. METHOD A. Tsting Points 16 fild tsting points wr slctd and distributd within th ara of first yard on Prambanan Tmpl as shown in Fig. 2. B. Constant Had Prmamtr Tst Th obtaind obsrvation data from th tst wr substitutd into Darcy quation: QL (1) hat 1339

Soil Moistur Dvic Instrumnt Calibration Th tsting procdur was conductd according to guidanc givn by th manufacturr.

2 whr A is sampl sction and Q is watr volum in masuring glass, h is th hight diffrnc of nrgy, t is flow tim, and L is sampl lngth or currnt lngth. Fig. 1 Unsaturatd hydraulic conductivity calculatd by th IP mthod as [4] Fig. 2 Locations of tsting points and sampling C. Soil Moistur Dvic Instrumnt Calibration Th tsting procdur was conductd according to guidanc givn by th manufacturr. Th calibration tst was conductd using ovn-drid soil collctd from first yard of Prambanan Tmpl. D. Laboratory Soil Prmability Tsting at Unsaturatd Condition This tst was prformd by crating a sampl of Prambanan Tmpl soil in a containr with crtain dnsity. Laboratory soil prmability tsting at unsaturatd condition was conductd using constant watr rsrvoir and containr and soil moistur snsor dvic instrumnt as th indicator of soil saturation in wtting and drying procss through th chang of volumtric watr contnt valus. Laboratory tsts wr prformd through two procss including wtting and drying. E. Dnsity Tst Th aim of this tst is to obtain th valu of fild soil dnsity. Sand con tsting was prformd for 16 tsting points. F. Prmability Tst and Volumtric Watr Contnt Masurmnt This tst aims to obtain th valu of fild prmability cofficint at ground surfac by using prmability tst instrumnt modl and dvlopd tsting procdur at 16 tsting points at th first yard of Prambanan Tmpl. Th masurmnt of volumtric watr contnt was conductd by using soil moistur snsor dvics instrumnt during th fild prmability tst procdur. Th masuring procss was initiatd from unsaturatd soil condition until soil had bcom saturatd. In addition to th instrumnt modl as [4], dvlopmnt and simplification of fild prmability tst instrumnt for sandy soil was also conductd. Rfrring to this rsult and laboratory constant-had prmability tsting concpt, th nw instrumnt modl, namd Constant Discharg modl, was cratd. In tsting procdur, using Constant Discharg modl as illustratd in Fig. 3, casing borhol was installd by staing casing pip to th soil with sampling dpth of 1D from ground surfac whr D is casing diamtr, thn followd by th installation of prmamtr pip. Th hight of sampl was qual to sampl diamtr or 1D basd on th prliminary tst rsults. Soil moistur snsor was stad blow casing. Aftr both pips and soil moistur snsor instrumnt wr proprly installd, data loggr was connctd to laptop and soil moistur snsor. Data intrprtation wr obtaind using data loggr dvic instrumnt to rad and sav volumtric watr contnt data. Th tst was prformd by maing an unsaturatd soil conditions to b saturatd, so that th watr discharg through th sampl would b qual to th initial discharg whn ntring prmamtr pip (Q = constant). Watr was flowd using constant watr rsrvoir and containr which was continuously flowd by watr with constant discharg through prmamtr pip. In this tst, it was assumd that groundwatr lvl was at th dg of sampl casing. Initial volumtric watr contnt ( 1 ) was bing rcordd. At a crtain tim, with constant flow discharg Q, watr lvl at prmamtr pip would bcom constant (H = constant), volumtric watr contnt 2 was thn obtaind. This tst was conductd by conditioning th soil from unsaturatd to saturatd condition. Th prmability cofficints wr calculatd by (2): Q (2) FH with, = cofficint of prmability of soil (cm/sc); Q = watr discharg (cm 3 /sc); F = gomtric factor (cm); H = hight of watr lvl insid th wlls (cm). According to [3], (2) was usd to calculat th prmability cofficint () at stady flow condition. Discharg usd in th calculation usd th discharg flow into th casing prmamtr. It was 1340

3 assumd that th watr tabl was locatd at th nd of th casing sampls. Thn for borhol conditions, th valu of F (gomtry factor) is according to [1], [3] calculatd by (3): D F 11L 1 D (3) TABLE I RESULTS OF PRELIMINARY TEST No Hight of sampl Typ of soil IF (cm/s) CD (cm/s) 1 0.5D SW-SM 1,97 x ,13 x D SW-SM 3,46 x ,15 x D SW-SM 3,51 x ,38 x D SW-SM 3,64 x ,61 x 10-3 with, R = radius of th wlls (cm); L = thicnss of xisting soil in th wll (cm). Th valu of unsaturatd cofficint of prmability ( unsat ) for any dpth of soil can b calculatd by (4) according to [2]: unsat z1 dz t 0 h 1 t whr h is prssur had, t is tim, z is dpth, and is volumtric watr contnt. Masurmnt of volumtric watr contnt valu was conductd by soil moistur prob until th watr lvl was constant or no significant changs. Valu of hydraulic gradint was assumd to 1.0 so it was not ncssary to now th paramtrs of Soil Watr Charactristic Curv which is quit xpnsiv. Tsting schm is shown in Fig. 3. Valus of prmability cofficint in unsaturatd conditions wr obtaind from numrical modls as [5] using quation: S (4) m r 1 (5) n s r 1 ah 0,5 1 / m S S 1 1 S s m 2 (6) whr, m = 1-1/n, S is ffctiv dgr of saturation, s saturatd volumtric watr contnt, r is rsidual volumtric watr contnt, s is saturatd prmability cofficint, and n ar mpirical paramtr. Equation (6) usually is namd as VG modl. Som unnown paramtrs wr masurd from Hydruss-2D data bas for sandy soil. G. Prliminary Tst Th tsting procdur plan considrd th valu of th gomtry factor and th sampl casing according to [1], [3]. Tsts wr conductd on sandy soil which was locatd in Dpartmnt of Civil Enginring, Faculty of Enginring, Univrsitas Gadjah Mada. Basd on prliminary tst rsults, th modl and tsting procdurs could b usd in th fild to masur cofficint of prmability. Th hight of sampl was qual to sampl diamtr or 1D basd on th as of installation of casing sampls, th disturbanc factor in soil sampls, th tsting duration, and th tst rsults that had bn rlativly good. Prliminary tst data ar shown in Tabl I. Fig. 3 Schm of th prmability tst instrumnt (Constant Discharg modl) IV.RESULTS AND DISCUSSION A. Calibration of Soil Moistur Snsors Instrumnt Calibration was conductd at th laboratory using soil from th first yard of Prambanan tmpl. Th calibration rsults of soil moistur snsor dvic ar shown in Fig. 4. B. Soil Proprtis Soil classification rfrs to Unifid Soil Classification Systm (USCS). Grain siz distribution tsting was prformd at 16 sampl points tan from soil of th first yard of Prambanan tmpl. Th tst rsult shows that thr ar two typs of soil at th first yard Prambanan tmpl which ar wll gradd sand-silty sand (SW-SM) and silty sand (SM). Spcific gravity tsting was conductd at both soil typs and it was obtaind that G s of SW-SM soil was 2.66 whil for SM soil was C. Laboratory Prmability Tst for Unsaturatd Condition Laboratory prmability tst in unsaturatd condition was prformd at SW-SM soil with dnsity of 18.0 N/m 3 and 19.8 N/m 3. Th tst rsult was corrlation of volumtric watr contnt () starts from wtting to drying procss and tim function (t) for SW-SM soil as displayd in Fig. 5. Paramtr s is volumtric watr contnt valu in saturatd condition and th valu of r nd to b prformd in trial for svral 1341

4 conditions. Ths trial conditions wr whn th soil was initially ovn drid with th valu of 4,5% and at th nd of th tst with th valu of 17%. Basd on (4) and (6), th corrlation btwn and can b obtaind. Basd on Fig. 5 th cofficint of prmability can b dtrmind. Fig. 6 shows th prmability cofficint with variation of volumtric watr contnt for sandy soil using constant discharg mthod. Th valu of prmability cofficint for unsaturatd conditions with a fild dnsity of 19.8 N/m 3 was in rang of 3 x 10-6 cm/sc (S r =68%) until 9.98 x 10-4 cm/sc (S r =82%). Fig. 4 Calibration of soil moistur snsor = 18.0 N/m 3 = 19.8 N/m 3 Fig. 5 Various volumtric watr contnt valu during prmability tst D. Fild Unsaturatd Cofficint of Prmability Basd on th valu of volumtric watr contnt changs during th tsting procdur loggd by soil moistur snsor instrumnt, th cofficint of prmability using constant discharg mthod for unsaturatd conditions could b obtaind. Paramtrs r usd in th calculation wr obtaind from th rsult of laboratory tst. Th fild unsaturatd cofficint of prmability of Prambanan tmpl yard with dnsity of 19.8 N/m 3 is shown in Fig. 7. As shown in Fig. 5, it is found that th influnc of various dnsity was not significant to unsaturatd soil. In th soil with diffrnt dnsitis, th diffrnc of saturatd volumtric watr contnt valu and rsidual volumtric watr contnt valu is lss significant. Fig. 6 Unsaturatd cofficint of prmability for sandy soil using constant discharg mthod Fig. 7 Fild unsaturatd cofficint of prmability of Prambanan tmpl yard From fild tsting rsult in unsaturatd condition, th data show that soil prmability cofficint valu in unsaturatd condition is incrasing along with th incrmnt of volumtric watr contnt du to lss ability of soil to flow watr during initial wtting. Th amount of watr, pntratd th soil during initial wtting, filld soil por cavitis which wr prviously filld with air so watr could not pass through th soil. Th dtrmination of prmability cofficint valu using VG modl is rquird som paramtrs which can b obtaind through tsting and modling. Th paramtrs ar s, r, and n. In this rsarch, comparison was mad btwn th graphic of vs and variation of r valu as shown in Fig. 6. It shows that th incrasing valu of r rsultd in mor vrtical curv and th dcrasing valu of r rsultd blow th curv. Th curv of wtting procdur is clos to curv of drying with th valu of r = 7,5% which is in vry dry soil condition. E. Effct of Soil Dnsity on Cofficint Prmability Soil dnsity lvl was masurd du to dry volum wight of th soil. Rlationship btwn cofficint of prmability valu and dnsity is shown in Fig. 8. Th rsult mainly shows th tndncy of dcrasing prmability valu for incrasing soil dns. 1342

5 F. Comparison of Prmability Cofficint Th valu of soil prmability cofficint in saturatd condition wr obtaind using proposd constant discharg mthod and convntional constant had mthod as laboratory standard. Tsting rsults ar shown in Fig. 9. In gnral, th valu of prmability cofficint which obtaind from proposd constant discharg mthod is highr than constant had mthod. Th diffrnc in prmability cofficint valus is mayb causd by th sampl dimnsion. This rsarch is still on primary stag. It nds a furthr study on ffct of sampl dimnsion. Fig. 8 Dnsity influnc against prmability Fig. 9 Tsting rsults in saturatd condition V. CONCLUSIONS Dvlopmnt of mor simpl quipmnt and procdur for in situ tsting to masur prmability undr both saturatd and unsaturatd conditions wr carrid out. Th quipmnt and tsting procdur dvlopd in this rsarch wr quit ffctiv, simpl, and asy to implmnt in obtaining fild soil prmability cofficint valu for sandy soil. Th proposd constant discharg mthod can b usd to dtrmin soil prmability cofficint from unsaturatd to saturatd condition without stablishing soil watr charactristic curv. Soil layr at th first yard of Prambanan tmpl is groupd as wll gradd and sand-silty sand. Cofficint of prmability with fild dnsity of 19.8 N/m 3 for unsaturatd conditions was in rang of 3 x 10-6 cm/sc (S r =68%) until 9.98 x 10-4 cm/sc (S r =82%) using proposd constant discharg mthod. Th corrlation btwn prmability cofficint and volumtric watr contnt () from unsaturatd to saturatd condition for sandy soil can b discovrd. In gnral, th valu of prmability cofficint which obtaind from proposd constant discharg mthod was highr than constant had mthod. Th diffrnc in prmability cofficint valus was causd by th sampl dimnsion. This rsarch is still in arly stag. It nds furthr study on th ffct of sampl dimnsion. Furthr rsarch about th influnc of sampl casing and prmamtr pip diamtr as wll as various sampl hights du to prmability cofficint is ndd. ACKNOWLEDGMENT Th authors xprss thir gratitud to Dirctorat Gnral Highr Education (DGHE) Ministry of Education and Cultur, Indonsia and Univrsitas Gadjah Mada for financial supporting by Comptitiv Grant of Intrnational Collaboration Rsarch and Publication with contract no. LPPM-UGM/1010/lit/2014, datd May 5, Th authors also would li to thans to collagus of Dpartmnt of Civil and Environmntal Enginring, UGM and Prsrvation Cntr of Cultural Hritag, Prambanan Unit for thir hlpful discussion and spirit in conducting fild and laboratory tsts. REFERENCE [1] Hvorslv, M.J., Tim Lag and Soil Prmabiity in Ground Watr Obsrvation. Watrways Exprimnt Station, [2] Richards, L.A., Capillary Conduction of Liquids Through Porous Mdiums. Physics, 1(5), p.318, [3] Sunjoto, S., Optimasi Sumur Rsapan Sbagai Salah Satu Pncgahan Intrusi Air Laut. In Sminar PAU-IT-UGM. Yogyaarta, [4] Tashita, Y. & Komatsu, M., Fild tchniqus for masuring fild saturatd and unsaturatd hydraulic conductivity using soil moistur profil in a final disposal sit, [5] Van Gnutchn, M.T., A Closd-form Equation for Prdicting Hydraulic Conductivity of Unsaturatd Soils. Soil Scinc Socity of Amrica Journal, 44, pp ,

15. Stress-Strain behavior of soils

15. Stress-Strain behavior of soils 15. Strss-Strain bhavior of soils Sand bhavior Usually shard undr draind conditions (rlativly high prmability mans xcss por prssurs ar not gnratd). Paramtrs govrning sand bhaviour is: Rlativ dnsity Effctiv