## 3 Results
### Slope Instability Processes with Different Soil Types  
Figure 7 shows the variation of water content, matrix suction, pore water pressure, and total stress of the slopes with different soil compositions. For the same rainfall intensity, there was no significant difference in the time at which the volumetric water content started to rise for the different soils. The volumetric water content for all of them started to increase  
Figure 6: Variation in measured data when rainfall patterns are different: (**a**) water content; (**b**) matrix suction; (**c**) pore water pressure; (**d**) total stress. at about 25 min. However, there were large differences in the final volumetric water content of the different soil types. The upper limit of the volumetric water content was the highest for the silty soil, at about 36%. The upper limit of the volumetric water content for the mixed soil was about 30%. The sandy soil had an upper volumetric water content of about 27%. The gravel soil had the lowest upper limit of volumetric water content, which was about 18%. The volumetric water content of the silty and mixed soils rose very quickly and reached their maximum water content at about 35 min. The volumetric water content of the sandy soil rose over a longer period of time and the rate gradually decreased. The volumetric water content of the gravel soil plateaued after a small increase. The initial matrix suction of the different soils showed great differences. The initial matrix suction of the fine-grained soils was higher than that of the coarse-grained soils. The initial matrix suction of the silty soil was about 78 kPa, that of the sandy soil was about 52 kPa, that of the gravel soil was only about 14 kPa, and that of the mixed soil was about 48 kPa. The changing processes of matrix suction were also different. The matrix suction of the silty soil at location I entered the diminished stage at about 28 min, decreased sharply in the time period of 30 \(\sim\) 40 min, and finally stabilized at about 20 kPa. The matrix suction of the sandy soil and mixed soil decreased at about 25 min and the matrix suction of the sandy soil reached the stable stage at 35 min with a value of 18 kPa. The matrix suction of the mixed soil continued to decline and finally decreased to about 8 kPa. The matrix suction of the gravel soil was very small and did not change significantly in the first 30 min of rainfall. It entered the fluctuating stage at 30 min. Figure 7: Variation in measured data when soil types are different: (**a**) water content; (**b**) matrix suction; (**c**) pore water pressure; (**d**) total stress. The soil type had a strong influence on the changing process of pore water pressure. The increasing process of pore water pressure was longer for the mixed soil. The peak occurred between 30 and 40 min and it reached about 4 kPa. The pore water pressure changes that were observed in the silty, sandy, and gravel soils can be divided into two stages: a rapid-increase stage and a stable stage. The increasing stage was seen in approximately the first 20 min of the test. When the increasing stage was over, the pore water pressure of the silty soil was greater than that of the sandy soil, and that of the sandy soil was greater than that of the gravel soil. The different soil types had different total stress values. At position I, the total stress was highest in the silty soil. It increased slowly during the time period from 10 to 40 min and remained constant at about 10 kPa during the time period from 40 to 60 min. The total stress of the sandy soil varied little in the first 20 min, increased and fluctuated in the time period from 20-50 min, and decreased abruptly at about 50 min due to the landslide. The total stress of the gravel soil was the smallest and it increased only slightly during the rainfall and then stabilized around 4 kPa. The total stress variation pattern of the mixed soil was similar to that of the sandy soil. Soil type is a key factor for determining the stability of slopes.