Evaluation of Unknown Tube Well Depth Using Electrical Resistivity Method

Abstract

Electrical resistivity method has increasingly adopted in engineering, environmental, mining and archaeological studies. Systematic and proper studies of unknown civil engineering structure evaluation particularly on tube well depth was rarely being established. Conventionally, camera test or string with weight approach has been used to evaluate unknown tube well depth thus exposed to several restriction due to its expensive and time consuming. Hence, this study focused on evaluation of unknown tube well depth using indirect test with particular reference to electrical resistivity method (ERM).A single spread line of electrical resistivity survey was performed using ABEM SAS 4000 equipment set based on Wenner and Pole-dipole array in line with the tube well position. Electrical resistivity raw data was processed using RES2DINV software producing electrical resistivity tomography (ERT) of the subsurface profile studied. Then, electrical resistivity value (ERV) obtained from RES2DINV analyses (ERT) was extracted and analysed using plotted graph (depth versus ERV) specifically at tube well position based on electrical resistivity spread line performed. It was found that both array have shown some good similarity results in term of tube well depth (20 m) thus able to verify the result interpreted. Both array have shown some good similarity of ERV representing groundwater (ERV = 10 - 100 Ωm) and soil with water (ERV > 100 Ωm) at depth of 0 - 20 m and >20 m respectively. All those interpretation have shown good agreement based on verification thru established ERV of earth materials references, geological map and nearest available boreholes data. Hence, this study has shown that the application of ERM was applicable in evaluation of unknown tube well depth which efficient in term of cost, time and environmental sustainable.