Numerical Modelling of Subsurface Cavities Using 2D Electrical Resistivity Tomography Technique

Abstract

The formation of subsurface cavities in karstic rocks causes serious engineering problems for shallow and deep foundations. These cavities restrict the urban development and trigger significant geotechnical and geoenvironmental hazards. In this work, 2D Electrical Resistivity Tomography (ERT) technique was adopted to simulate subsurface cavities commonly formed in limestones using Wenner, Wenner-Schlumberger and Dipole- Dipole arrays. Air and water filled cavities were modelled utilizing blocky L1 norm and smooth L2 normoptimization methods. The results showed that subsurface cavities can well be detected particularly at low resistivity noise levels. Their geometry and position are reasonably indicated using L1 norm method due to the sharp resistivity variations especially for air filled cavity model while L2 norm method produces gradual resistivity boundaries for both air and water filled cavities. Dipole- Dipole array and L1 norm method perform better in delineating geometry and position of both air and water filled cavities. It is suggested that ERT technique using Dipole- Dipole array, as non- invasive tool, can be adopted for detecting subsurface cavities in karstic rocks to avoid the catastrophic effects of these features.