Soundness Evaluation of Ground Conditions Inside Decrepit Slopes by Conversion Analysis of Geophysical Data

In Japan, many of the slopes covered with shotcrete have aged considerably. Therefore, there is a risk that slope failures may occur due to the effects of factors such as seasonal weather patterns, natural disasters, climate change, heavy rainfall, and earthquakes. Therefore, it is important to develop a method for monitoring the stability and the durability of these slopes. In this paper, we propose a technique (hereafter referred to as "conversion analysis") that converts seismic velocity and electric resistivity data to porosity and saturation, which is then used to monitor weathering and groundwater fluctuation behind the slope. There have been several studies regarding the empirical relations between geophysical parameters such as seismic velocity and resistivity, and engineering properties such as porosity and saturation. At the investigation sites, seismic tomography and resistivity tomography were carried out between the ground surface and the boreholes. Investigation was conducted a total of 5 times, once in the summer and once in the winter for 3 years. As the results, it was possible to monitor the signs of seasonal variation and weathering in the ground.