## 4 Results and Analysis  
### Geoelectric Field Characteristics under Disaster Source Evolution in the Survey Line Area  
The structure of the slope rock and soil mass changes during the wetting and drying cycle and is gradually destroyed to generate geological disaster sources such as cracks or aquifers. In the drying process, the porosity of the rock and soil mass decreases, and cracks are produced. In the wetting process, the porosity increases, and cracks decrease. When the water discharge rate is lower than the infiltration rate, an aquifer is formed within the slope [24]. From the overall change trend, the apparent resistivity of the slope at each depth showed a downward trend in the rainfall process, namely, the apparent resistivity of the slope decreased with increasing rainfall process and water infiltration and finally tended to stabilize. With increasing depth, the time of apparent resistivity decline correspondingly increased. In the process of apparent resistivity decline, obvious abrupt changes and fluctuations occurred. Relevant research has shown that the influencing factors of rock and soil resistivity include the porosity, water content, saturation, temperature, water composition, rock and soil composition and structure, among which the porosity and saturation are the main influencing factors [25,30]. Under the test conditions, the temperature, water composition and geotechnical composition were fixed parameters, and the slope resistivity varied under the influences of the porosity, water content, saturation and internal structure. Figure 6: _Cont._  
Figure 6: Resistivity-rainfall sequence diagram of sections B, C, D, E and F.  
Figure 5 shows the relationship between the resistivity and rainfall sequence of sections A, E and G. As shown in Figure 5, after the fifth rainfall process, the apparent resistivity of each layer of the slope exhibited a significant sudden decline for the first time. The apparent resistivity of each layer slightly increased after decreasing. The apparent resistivity in the area at a depth of more than 0.035 m decreased to approximately 40 \(\Omega\cdot\)m, and ponding occurred at the top of the slope, indicating that the shallow slope rock and soil mass was nearly saturated. The sudden decline in the apparent resistivity at the beginning of rainfall occurred because with rainwater infiltration, the pores of the shallow slope rock and soil mass were rapidly filled with water, and conductive ions in the rock and soil entered the pore water. At the same time, because the conductivity of water is far higher than that of the rock and soil, the conductivity in the shallow area rapidly increased, and the apparent resistivity rapidly decreased. Affected by the increase in the saturated gravity of the upper slope, the deep rock and soil mass was compacted, the connectivity and conductivity were enhanced and the apparent resistivity in the deep area was reduced. At the measurement stage (after rainfall cessation), the loss of water from the slope resulted in uneven shrinkage of the rock and soil mass pores. When the shrinkage stress exceeded the tensile strength of the rock and soil mass, shrinkage cracks could form. In the rainfall process, water absorption and expansion of the rock and soil mass resulted in a loose arrangement of particles and an increase in the pore volume. When the expansion stress exceeded the tensile strength of the rock and soil mass, expansion cracks could occur [31; 32; 33]. The development of cracks led to a decrease in the electrical conductivity of the rock and soil mass and an increase in the potential difference, manifested as the increase in the resistance in the crack area and the apparent resistivity increased. That is, the resistivity in the fracture area increased with crack development [34; 35]. After the 96 th rainfall event, the apparent resistivity of section E of the shallow slope from 0.035 m to the top of the slope sharply increased and then fluctuated.