Assessment of ground subsidence potential at problematic culvert on expressway: Case study using Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR)

Potential of ground subsidence assessment was carried out at problematic culvert on expressway. The assessment was conducted using Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) in cooperation with Preston GeoCEMSdn Bhd. This paper described both of the methods used in this study. The aim of this study to obtain subsurface strata profiling around 10 to 15-metre depth. In this case, the ERT Gradient protocol survey was conducted to achieve the subsurface profiling at 15-meter depth and GPR forward line survey at 10-meter depth subsurface profiling. Total eight (8) resistivity lines across the site with the length of 80 meters each were conducted to suit the site condition. Meanwhile, total ten (10) GPR lines were conducted at the same location. Indication of the soil/rock are in saturated condition was based on resistivity value GPR radargram.ERT and GPR results showed low resistivity values and low amplitude at the saturated zone which indicated ground subsidence on top of the culvert area. The problem occurs may due to the saturated material and low groundwater level at the area.