Site suitability for engineering-infrastructure (EI) development and groundwater exploitation using integrated geophysical approach in Guangdong, China

This study describes the efficiency of an incorporated geophysical approach involving ERT (electrical resistivity tomography), magnetic, induced polarization (IP), and self-potential (SP), with a view to investigate subsurface of a highly heterogeneous site for EI (engineering infrastructure) development and groundwater exploitation in Huidong County, Guangdong, China. The subsurface formation can be delineated using boreholes; however, such approaches are time consuming, expensive, and cannot be carried out in the steep topographic areas. The proposed geophysical approach can decrease significant number of boreholes to evaluate the most problematic geologic structures. The geophysical data were acquired via a variety of survey parameters along four profiles. A least-squares inversion technique was used for the post-processing of geophysical data to generate 2D/3D models of the subsurface geologic units. ERT/magnetic results combined with borehole data delineated four distinct layers with specific resistivity range, such as the topsoil cover, the highly weathered layer, the semi-weathered layer, and the fresh bedrock. Incorporation of ERT/magnetic models with IP and SP delineated several localized fractures/faults. Empirical equations were obtained to estimate hydraulic conductivity of the weathered layer. The integrated results propose that groundwater is the best accessible in weathered/fractured zones, whereas such zones are unsuitable for the construction of engineering infrastructures. The geophysical results show high correlation with accessible upfront borehole information of the investigated site. The study suggests that this integrated approach can be used as a useful tool in any heterogeneous site for suitability of EI development and groundwater exploitation.