Combined ERT and GPR Data for Subsurface Characterization of Weathered Hilly Slope: A Case Study in Zhejiang Province, Southeast China

Abstract

Rain-triggered landslides frequently threaten public safety, infrastructure, and the economy during typhoon seasons in Zhejiang Province. Landslides are complex structural systems, and the subsurface features play a significant role in their stability. Their early identification and the evaluation of potential danger in terms of the rupture surface and unstable body are essential for geohazard prevention and protection. However, the information about the subsurface acquired by conventional exploration approaches is generally limited to sparse data. This paper describes a joint application of ground-penetrating radar (GPR) with a 100 MHz antenna and the electrical resistivity tomography (ERT) method with the Wenner configuration to identify the stratum structure and delineate the potentially unstable body of a clay-rich slope, the results of which were further verified using borehole data and field observation. The acquired results from the GPR and ERT surveys, consistent with each other, indicate two stratigraphic layers comprising silty clay and silty mudstone. Moreover, the potential rupture zone very likely exists in the highly weathered mudstone in the depth range of 3–7 m, and the average depth is 5 m. In addition, the thickness of the unstable mass is greater on the east and crest parts of the slope. Conclusively, the optimum combination of ERT and GPR is reliable for conducting rapid and effective delineation of subsurface characteristics of clayey slopes for risk assessment and mitigation during the typhoon season.

Groundwater identification using geophysical tools and its implications for the stability of slopes in an open pit mine

“…Geophysical methods, such as DC (Direct Current) resistivity, have been widely used to map fractured aquifers on rock mass (Porsani et al, 2005; Gomes de Oliveira et al 2014;Hamdan et al 2014;Moreira et al 2016;Pádua and Campos 2020;Whiteley et al 2021;Yan et al 2022). Frequent events of intense precipitation, as recorded in tropical climate countries, can aggravate the risk of rupture from the elevation of pore pressure in the rock mass (Corrêa et al 2021;Sun et al 2021;Wyllie and Mah 2004).…”