GEOTECHNICAL RISK ASSESSMENT OF SUBSURFACE CAVITIES IN LIMESTONE FORMATIONS USING 2D ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT) FOR INFRASTRUCTURE DEVELOPMENT IN KAMPAR, PERAK DARUL RIDZUAN, MALAYSIA

Abstract

Subsurface cavities in limestone formations poses hazardous risks to infrastructure from sudden ground movement, subsidence, and structural failure. These cavities form mainly from natural dissolution of carbonate rocks. Traditional methods like borehole drilling are costly, limited in resolution, and require many boreholes to cover large areas. To address this, the utilisation of 2D Electrical Resistivity Tomography (ERT) as a non-invasive geophysical technique to investigate potential subsurface voids at a proposed site in Taman Bandar Baru, Mukim Kampar, Daerah Kampar, Perak Darul Ridzuan, Malaysia. Three survey profiles (L-1,L-2, L-3) were conducted using a dipole-dipole array, and data were analysed with RES2DInv software to produce subsurface resistivity profiles. Geological formations identified through resistivity ranges revealed weakly consolidated soils, weathered or fractured limestone bedrock, and water-filled cavities, all indicating potential instability. A risk matrix applied to each profile confirmed that zones with groundwater activity and voids pose a high collapse risk to surface layers. The study highlights the value of early ERT and geotechnical risk assessments for guiding mitigation strategies, recommending continuous monitoring, adapted designs, and best practices to reduce hazards.