Study on moisture migration in natural slope using high-density electrical resistivity tomography method

Groundwater is an important factor affecting landslide deformation and instability. At present, the research on water transport process of natural slope mostly relies on sensor monitoring or numerical simulation, which can not fully meet the requirements of non-disturbance and fast measurement. In this study, a natural slope is tested using high-density electrical resistivity tomography (ERT) method and time-domain reflectometry (TDR) to obtain the water content in the slope, and the relationship between electrical resistivity of soil and water content is revealed. Furthermore, the distribution and migration characteristics of underground water in slope are inverted and analyzed. Sequentially, the capability of ERT in capturing moisture migration and distribution is verified. Results of in-situ tests show that: water content of soil has obvious logarithmic relation with soil's resistivity. Moreover, the effective infiltration or evaporation depth of this slope is 2 m, and water content gradually decreases when the depth is greater than 2 m. The main reason for the sharp increase of water content between 1.3m-2m depth under moderate rainfall intensity is the preferential flow through a crack at the back edge of slope. It is also found that the transition zone between highest water content (lowest resistance zone) and lowest water content (highest resistance zone) is highly consistent with the position of sliding zone in subsequent failure of slope.