Subsurface Profile Mapping using 3-D Compressive Wave Imaging

Abstract

Geotechnical site investigation related to subsurface profile mapping was commonly performed to provide valuable data for design and construction stage based on conventional drilling techniques. From past experience, drilling techniques particularly using borehole method suffer from limitations related to expensive, time consuming and limited data coverage. Hence, this study performs subsurface profile mapping using 3-D compressive wave imaging in order to minimize those conventional method constraints. Field measurement and data analysis of compressive wave (p-wave, vp) was performed using seismic refraction survey (ABEM Terraloc MK 8, 7 kg of sledgehammer and 24 units of vertical geophone) and OPTIM (SeisOpt@Picker & SeisOpt@2D) software respectively. Then, 3-D compressive wave distribution of subsurface studied was obtained using analysis of SURFER software. Based on 3-D compressive wave image analyzed, it was found that subsurface profile studied consist of three main layers representing top soil (vp = 376 – 600 m/s), weathered material (vp = 900 – 2600 m/s) and bedrock (vp > 3000 m/s). Thickness of each layer was varied from 0 – 2 m (first layer), 2 – 20 m (second layer) and 20 m and over (third layer). Moreover, groundwater (vp = 1400 – 1600 m/s) starts to be detected at 2.0 m depth from ground surface. This study has demonstrated that geotechnical site investigation data related to subsurface profiling was applicable to be obtained using 3-D compressive wave imaging. Furthermore, 3-D compressive wave imaging was performed based on non destructive principle in ground exploration thus consider economic, less time, large data coverage and sustainable to our environment.

Keywords

• Site investigation
• compressive wave
• seismic refraction