Application of geophysical methods to evaluate soil dynamic properties in Penang Island, Malaysia

The essential criterion of selecting the site for building foundations is the underlying soil. This vital requirement stems from the associated potential for disaster should the ground condition be unstable. Conventionally, the method of geotechnical drilling is used in soil investigation work. However, this method is limited to providing subsurface information only at one particular point. This research aims to utilise geophysical methods to investigate the soil dynamic properties of various lithology types via application of electrical resistivity method (ERM), seismic refraction (SR), and multichannel analysis of surface wave (MASW) methods. The soil dynamic properties (bulk density, Poisson's ratio, Young's modulus, shear modulus, bulk modulus) and material bearing capacity (subgrade reaction coefficient, ultimate and allowable bearing capacity) were computed using a relative formula by using compressional wave (VP) and shear wave velocities (VS). The calculated values of soil dynamic properties and material bearing capacity for the three study areas are capable in determining the competency and stiffness of subsurface layers for building foundation. The results leading to this conclusion can be verified by the values of standard penetration test value (SPT-N) from borehole record. From this study, it is apparent that the soil dynamic properties and material bearing capacity values are essential to determine the competency of soil, in turn aiding in determining the area suitable for the shallow foundation to rest. Thus, geophysical methods are time- and cost-saving, as well as non-intrusive, recommended for site investigation before starting any construction work.