## 1 Introduction  
The rainy season exhibits a high incidence of geological slope disasters. Geological slope disasters such as debris flows and landslides are readily formed, especially under continuous rainfall [1, 2, 3, 4]. Research has shown that in the rainfall seepage process, the rock and soil mass bulk density and the pore water pressure increase, the sliding force of the slope body increases, and the shear strength decreases, resulting in slope failure [5, 6]. Cracks and weak planes formed during rainfall and seepage are the main geological disaster sources driving slope failure [7, 8]. Determination of the geological conditions and change trends of the slope structure, lithology, crack development, water content and weak planes is essential for effective slope disaster prediction and forecasting. Scholars have widely researched the geological hazards of rainfall-affected slopes. [PERSON] et al. [9] used geostatistical techniques to study the geological strength index distribution in mine slope rock masses and analyzed the correlation between the spatiotemporal variability characteristics of rock mechanical parameters and the development of geological slope hazards. [PERSON] et al. [10] employed comprehensive geophysical exploration techniques, namely the high-density electrical method and geological radar method, to survey the factors influencing the instability of open pit mine slopes. The impact of groundwaterseepage on the stability of mine slopes was analyzed. [PERSON] et al. [PERSON] et al. (2011) found that the generation of cracks in the rainfall seepage process is the key factor inducing slope instability, and most landslides occur during or shortly after rainfall. [PERSON] et al. [PERSON] et al. (2012) studied the progressive failure mode and water transport behavior of slopes under rainfall seepage and examined the slope disaster mechanism controlled by cracks. The research results showed that the slope stability decreases with increasing initial crack depth and gradually decreases with increasing soil saturation ratio, finally resulting in a slope disaster. [PERSON] et al. [PERSON] et al. (2013) investigated the response relationship between the water content in slope soil, pore water pressure, displacement and the rainfall process, infiltration trend and disaster mode through physical model tests. The change in the soil moisture content in the rainfall-affected slope exhibited a lag, and the slope displacement was significantly positively correlated with the change rate of the water content. The mechanism of slope disasters can be divided into three processes: scattered collapse of the steep slope, formation of tension cracks in the slope and large-scale collapse. Due to its advantages of rapid and nondestructive detection, the high-density resistivity method has been widely adopted in the study of underground media. [PERSON] et al. [PERSON] et al. (2014) studied the underground resistivity distribution in a slope and mapped the potential risk areas of geological slope hazards. Weak zones were characterized by a large proportion of high water-saturation zones and low resistivity values. [PERSON] et al. [PERSON] et al. (2015) established a soil resistivity test method for conventional and supergravity environments based on the high-density electrical method, studied the correlation between the seepage soil resistivity and water content, and verified the effectiveness of the high-density electrical method in the detection of soil moisture migration. [PERSON] et al. [PERSON] et al. (2016) examined the relationship between the water content and resistivity of slope soil by combining the high-density electrical method and time-domain reflection technique, revealed the distribution characteristics and migration trend of slope groundwater, and realized rapid and nondestructive detection of slope water migration. [PERSON] et al. [PERSON] et al.