Soil Investigation for Determining Aquifer Position at Pasir Impun Area, Bandung, West Java Using Resistivity Method Wenner Configuration

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1 Jnury 2, 216 Soil nvestigtion for Determining Aquifer Position t Psir mpun Are, Bndung, West Jv Using Resistivity Method Wenner Configurtion Diyn Prwtiningtys,,*, Dsmo, nd Achmd Sjmsuri, ) Lecturer t Deprtment of physics, Fculty of Engineering, Mthemtics nd Nturl Sciences, ndrprst PGR University, Jkrt, ndonesi *Corresponding uthor: dine.tys@gmil.com, university@unindr.c.id Pper History Received: 23-December-215 Received in revised form: 5-Jnury-215 Accepted: 2-Jnury-216 ABSTRACT At this time, we owning mny geophysics methods tht cn be used to optimize investigtion nd nturl source explortion under lyer surfce, one of them is Georesistivity method. Georesistivity method is one of geophysics method tht study bout electricity in the erth nd lso to detect n object in the surfce lyer re of erth. The following, technology is showed to investigtion nd nlyzed quifer t botnicl grden re, Mekrmnik villge, Psir mpun, Est Bndung West Jv, using Georesistivity method, Wenner Configurtion. n this reserch, will be do Georesistivity method with Wenner configurtion nd be processed with using inversion from softwre Res2DV, nd sopch quifer contour mpping, which previous be done the topogrphy correction. Bsed on the inversion obtined, we be obtin to interpret some points which showed quifer position, re s follow : 1). Line 1 on loction 1, with the distnce of extend is between metre on surfce lyer. (t hs medium quifer) which the resistivity is 8 ohm metre, nd lso hs porosity nd volum vlue 25% nd 945,9 m3 with the depth is 6 metre. ts formtion rocks t this loction re sndstone, nd limestone, nticline topogrphy, dominted by norml fult which the trend is NE-SW. 2). Line 6 on loction 1 (The highest quifer) with the distnce of extend is between metre metre, which the resistivity is 1 3 ohm metre, porosity nd volum vlue re 18,26% nd 116,85 m3, with the depth trget is 7 metre. ts formtion rocks t this loction re sndstone, lluvil nd limestone, syncline topogrphy, dominted by norml fult which the trend is NE- SW. And then the third is line 8 on loction 2 with the distnce of extend is between metre, the resistivity is 1 ohm metre, which its porosity nd volum re %, nd 264 m3, with depth trget is 35 metre. t hs undultion topogrphy which the trend is SE SW dominted by norml fult, nd its formtion rocks re tuff, sndstone, grvel formtion. KEY WORDS: Geologicl stucture condition, Geophysich method of Wenner Configurtion, nterprettion for quifer position. NOMENCLATURE NE SW m 3 V mv ma North Est South West Metre Cubic Apprent Resistivity (Ohm.m) Voltge (mv) millivolt Electric Current (ma) milliampere Geometric Wenner fctor (metre) 1. NTRODUCTON Wter hs n importnt role to humn life. Almost 9% humn life needs wter, becuse it is needed for humn body, wter trnsporttion tool, industry, genertor, nd irrigtion. Tlk bout wter usge, in cse tht hppen t Mekrmnik Villge, the study re is botnicl grden, locted in Psir mpun Est 13 Published by nterntionl Society of Ocen, Mechnicl nd Aerospce Scientists nd Engineers

2 Jnury 2, 216 Bndung, in West Jw Province, where the society in its round is difficult to obtin wter. One of the obstcle's fctor is difficulties of the geologicl structure nd soil condition t the re, cusing some people difficult to find the position of wter resources. Tectonic intensity in this re is very high dominted by nticline structure with direction trend from west to est, (NWW-SEE). This Are is norml frcture, which its direction trend is sme with nticline structure nd its penetrtion into bsement. Psir mpun consist of reservoir rock which its velocity is moderte (smller thn subsidence velocity) nd its rock formtion is limestone, colory grey (Hrsono nd Fudi, 25). Beside tht, this loction ws formed from volcno residul soil, consisted of breksi, tuff, tuff''s grin, snd stone, dust. Some types of its soil re : Red cly, nd grey volcno soil (Wesley, 21). To overcome this problem, we conducted necessry geophysics method to interpret geologicl structure nd found the informtion bout the loction of wter resources position in this re. One of the mentioned method is georesistivity method. Georesistivity method is one of the geophycics methods tht study bout electricity flow inside the erth nd to detect it in the erth surfce (n this mtter to potentil mesuring, current mesuring, nd elektromgnetic's field) which hppen nturl or cused by current injection into the erth. Exmple : Self Potentil method, Telluric current, Mgnetotelluric, Electromgnetic, nduce Polriztion (P), Resistivity method, etc. n this reserch, to identifiction the loction of wter resources in this re, we using Georesistivity method, Resistivity Sounding. t lso known s Drilling Resistivity, Probing Resistivity, nd etc. This method is studying bout resistivity rock under erth surfce ccording to verticl direction. n this method, sounding point mesurement be done with chnged the distnce of electrode. To chnge the distnce of electrode, be done beginning from the smllest distnce until the lrgest distnce ccording to grdul. Electrode's distnce is comprble with the deepness of erth surfce lyer which detected. t mens, if the distnce of electrode is lrge, then the erth surfce lyer will be deeper. Sounding Resistivity, ws fmilir known s vrious of kind electrod's configurtion. Among its re : Wenner's Configurtion, Schlumberger, Bipol-dipol, Lee Prtision, Line Source, grdien's System 3 point, etc. n this reserch, our im is to nlyze geologicl structure condition t botnicl grden Mekrmnik villge, Psir mpun, Est Bndung, nd to find the loction of the wter resources, using georesistivity method, with Wenner configurtion. The loction mp of quifer investigtion is shown in figure GEORESSTVTY METHOD WTH WENNER CONFGURATON Georesistivity method Wenner configurtion be found by Wenner in 1915, nd being fmous in Americ. This Configurtion could be done for resistivitiy mpping nd lso resistivity sounding. (Adm, A nd Hendrjy L. 25). this configurtion type be done ccording to the limit vlue. Exmple, if the erth is flt, Wenner configurtion must be reltive for the flt re on its surfce. But f this configurtion is pplied to the oblique surfce, we must need some vlid correction. For Wenner configurtion, the current electrode nd potentil electrode ws showed on figure 2 below. n this mtter, the current electrode nd potentil electrode ws set ccording to symmetricl in sounding point. And the distnce of current electrode is triple from the potentil electrode distnce. As smple, if the distnce of ech potentil sounding point is /2, then the distnce of ech electrode current in sounding spot is 3/2. We must remembered tht the fourth of electrode s with sounding point must be on one line. On resistivitiy mpping, the spce of electrode s distnce is not chnged for every sounding point (its lrge for this distnce is constnt). Then for resistivity sounding, spce distnce of electrode s is to be lrge ccording to grdul, beginning from smll vlue, for sounding point. Electrode s spce is depend to the tool bility which be used. f the current flow result more sensitive nd lrge, it is cusing the tool become free to mesuring the spce of the electrode s distnce, which it lrger nd effecty to the deep on surfce lyer (be deeper). Configurtion Wenner type, cn to detect un-homogen locl from the loction. V A M N B Figure 2: Wenner Configurtion Bsed on figure 2, configurtion Wenner geometry fctor cn be expressed with defined s follow : Figure 1: Loction mp of Mekrmnik Villge. K w = 1 AM 1 B M 2π 1 A N 1 + B N 14 Published by nterntionl Society of Ocen, Mechnicl nd Aerospce Scientists nd Engineers

3 Jnury 2, 216 = 2π =2π (1) Then for Wenner Configurtion eqution is : Where : V ρ w = 2π ρ w = Resistivity on Wenner configurtion. ΔV= Potentil Voltge (Volt). = Electric Current (Ampere). (2) electric switch to 2. 8). Beginning to mesuring with sw the voltge counter digitl (volt), nd rrnge the compenstor Corse until the voltge vlue become zero. 9). f the voltge vlue lredy zero, press the button Strt until be obtined current vlue (ma) re constnt, fter tht press button Hold. We Registered the mesured dt nd then V dt, to form cuitition dt. 1). Chnge the electric switch on position 1, 2, V1, nd V2 to switch box which sme with cuitition dt, until be obtined ll the dt vlue tht to be wnted. On this method, electrode configurtion tht to be used is Wenner configurtion, is shown in figure RESEARCH METHODOLOGY The reserch re is t Botnicl Grden Mekrmnik Villge, Cimenyn district, Psir mpun Est Bndung West Jv Province, which locted t 6o S 17o E. This reserch method consist of two prt. 1. Pre Processing : On this phse we do some investigtion t reserch loction. this nvestigtion ws do to nlyze geologicl structure nd the chrcteristic of wter flow. Then from this phse, we mpping 9 line for wter trck in horizontl direction (is shown in figure 7). nvestigtion to recognize loction ws strted from erly Jnury until 3 June Dt Processing : We mesuring nd tking the georesistivity dt lso topogrphy dt in ech line tht hve been determined from 1th until with 5th on july 214. And then, from jnury until 9th september 215 the dt be processed with using inversion from softwre Res2DV, nd sopch quifer contour mpping, which previous be done the topogrphy correction nstrumenttion And Mesurement Systems nstrumenttion which used re : 1. Resistivity meter Nniur (NRD) multichnnel ( is shown in figure 3) s tool to write the current injection nd potentil of erth tht mesured. 2. Switch box, s position domer tool ctive electrode. 3. Accu 12V, s DC current source. 4. Electrode 31 piece, s current conducter nd voltge from the tool. 5. Cbel to conduct the current nd the swich box. 6. Hmmer, hndy tlky, rolemeter, nd GPS (Globl Potition System). the Procedure for georesistivity mesured is defined s follow (is shown in figure 4) : 1). Putting Resistivitymeter Nniur between electrode t point 21 nd 22. 2). Connecting the Resistivitymeter, switch box, nd ccu 12 V with connecter cble. 3). Embed the electrode t the point tht hve been mrked with wood pole. 4). Connecting the cble with switch box, to extended out nd then be connected with electrode. 5). Lit the Resistivitymeter nd scertin the voltge is lredy connected with ccu nd electrode current. 6). f the Glvnometer needle ws not on the red color, then one of elektrod current ws not embed well on surfce lyer. 7). Ascertin the electrode is lredy connected with switch box, with chnging one of electric switch on position 1 nd the other Figure 3: The nstrumenttion of Nnniur NRD Multichnnel. Figure 4: Mesuring Procedure for the nstrument. Figure 5: Georesistivity method, Wenner Configurtion is the distnce between the electrode in which tht the vlue ws chnge nd depending on the extend tht to be wnted. Every vlue ws chnge, so tht the dtum point become different. On this investigtion, distnce between its electrode is 6,5 meter nd for its extend foldness more less up to 2 meter. For withdrwl dt t this re, we obtined the vlue of V (voltge) 15 Published by nterntionl Society of Ocen, Mechnicl nd Aerospce Scientists nd Engineers

4 Jnury 2, 216 nd (current) tht ws red from instrument, nd fter be fold with Ks (Geometric Fctor), be obtined the ρ vlue (pprent resistivity). The eqution to obtin pprent resistivity vlue is (Adm, A nd Hendrjy L. 25) : (3) where : : Apprent Resistivity (Ohm.m) : Voltge (mv) : Current (ma) : Geometric Wenner fctor (metre) (i) Figure 7. (i) Line mp on loction 1. (ii) Line mp on loction 2 (ii) ( 2 ) which is electrode spce. Next, this vlue will be processed using the softwre Res2Div nd sopch contour mpping. The result ws showed on imge enhncement, which this result will be interpreted be ssist with geologicl mp. () 4. DESCRPTON AND DATA PROCESSNG For the phse of dt processing, we using Microsoft Excel softwre to clculte the pprent resistivity on ech dtum point. After pprent resistivity be obtined, the mentioned vlue be mde in Notepd formt ccording to formtted dt input from softwre tht will be used for dt processing (t ws explined in figure 6). (b) Figure 8. The Resistivity Section for Aquifer prospecting re t line 1 (), line 6 (b), loction 1 nd lso line 8 (c) loction 2. (c) Figure 6: Exterminte bd dtum point Dtum point vlue on red encircled is the bd vlue. Becuse of tht, be done exterminte for bd option of dtum point. And then, we do the inversion process to line dt using Res2dinv with Lest-Squres nversion method to found the imge of resistivity section (is shown in figure 8) nd sopch Aquifer mpping contour (is shown in figure 9). Finlly, the Result from this processing re : The informtion of resistivity vlue, topogrphy, litology, estimte of penetrtion depth from surfce lyer, porosity nd volum for quifer informtion on ech line. Dt processing result shown in the tble 1. below : Figure 9. sopch Aquifer Countur Mpping for Loction 1 At Cikwri, Mekrmnik Villge 16 Published by nterntionl Society of Ocen, Mechnicl nd Aerospce Scientists nd Engineers

5 Jnury 2, on loction 2 with the distnce of extend is between metre, the resistivity is 1 ohm metre, which its porosity nd volum re %, nd 264 m 3, with depth trget is 35 metre. t hs undultion topogrphy which the trend is SE SW dominted by norml fult, nd its formtion rocks re tuff, sndstone, grvel formtion. ACKNOWLEDGEMENTS Figure 1: sopch Aquifer Countur Mpping for Loction 2 At Cikwri, Mekrmnik Villge. Tble 1: nformtion of Resistivity (ρ), litology (σ), topogrhpy (T), porosity (φ (%)), depth (D (m) nd volum (V (m 3 )) quifer from ech line t loction 1 nd loction 2. LNE/ LOC 1/1 2/1 3/1 4/1 5/1 6/1 7/2 8/2 9/2 LOC AT ON 1 & 2 Ρ Σ T Φ D V Undultion 25 18,26 11,95 1, We sy Thnk God the Almighty one nd lso thnks to DPPM DKT s fund contribution nd the Omse comitte who hve given us the opportunity to lod pper into the proceedings. Likewise, we sy thnks to the tem of workers in geosurvey t the Botnicl Grden, Mekrmnik Villge, Cikwri, Psir mpun West Jv, nd the reserch tem, for the trust to to mnge the wter resources of Botnicl Grden re, well. God will repy you ll. REFERENCES 1. Adm, A nd Hendrjy L. 25. Georesistivity Explortion Method, Opertionl book, Geophysich Deprtement, TB Bndung. 2. Geoelectricl Opersionl Book, Mnul Mode ES-G1 OXO Geophysicl Prospecting Hrsono nd Fudi S. 25. Appliction Method on Anisotrophy Resistivity t Bngon Villge, Blor, Centrl Jv, Opertionl book., Geophysich Deprtement, TB Bndung, on Mrch, Physicl Geology. Opertionl book, Geophysich deprtement, TB Bndung, P.H Silitong, Geologicl Mp Of The Bndung Qudrngle, Jv, Geologicl reserch nd Deprtement Centre, Wesley, L.D. 21. An Overview of Residul Soils in Jv, ndonesi, nd mpliction for the nterprettion of n Situ Test. Proceeding Geotechnicl Pile 25. Deprtement of Civil Engginering Ktholik Prhyngn University, Bndung, CONCLUSON Bsed on the inversion dt processing obtined (is shown in tble 1), we interpret some points which showed quifer position, which it be ssist with geologicl mp. Are s follow : 1). Line 1 on loction 1, with the distnce of extend is between metre on surfce lyer. (t hs medium quifer) which the resistivity is 8 ohm metre, nd lso hs porosity nd volum vlue 25% nd 945,9 m 3 with the depth is 7 metre. ts formtion rocks t this loction re sndstone, nd limestone, nticline descend topogrphy, dominted by norml fult which the trend is NE-SW. 2). Line 6 on loction 1 (The highest quifer) with the distnce of extend is between metre metre, which the resistivity is 3 ohm metre, porosity nd volum vlue re 18,26% nd 116,85 m 3, with the depth trget is 6 metre. ts formtion rocks t this loction re sndstone, lluvil nd limestone, syncline descend topogrphy, dominted by norml fult which the trend is NE-SW. And then the third is line 17 Published by nterntionl Society of Ocen, Mechnicl nd Aerospce Scientists nd Engineers