Abstract
The instability of the bank slope of the reservoir will cause great loss to the life and property of the people in the reservoir area. The landslide of the reservoir not only occurs in the period of water level plummeting, but also occurs in the period of water level rising. In this paper, the mechanism of slope landslide in the rising stage of water level was studied from the perspective of soil disintegration in water. A series of tests on the disintegration of prisms and cylinders with the same volume and different bottom side lengths (diameter) were carried out. The results show that the specific surface area of the same volume sample was different, and the disintegration behavior was different. The larger the specific surface area of the same shape sample was, the faster the disintegration speed was. The deeper the water depth was, the shorter the disintegration time was under the same initial conditions. It shows that when the water level of the reservoir rose, the deeper the water depth was, the greater the pore osmotic pressure was, and the more the soil mass of the slope collapsed. This led to the reduction of the pressure on the lower part of the slope, the decrease of the antisliding force of the soil, and the failure of the slope.
Highlights
E disintegration of soil, known as wetting in geotechnical engineering, refers to the phenomenon of disintegration and collapse of soil after being immersed in water [11]. e disintegration of soil mass is due to the inconsistent thickening rate of the diffusion layer between particles after the soil is submerged in the water, which makes the repulsion force between particles exceed the suction force, and the soil mass collapses along the surface with the largest repulsion force [12]. e soil mass would collapse when encountering water, which would cause bank slope instability and endanger the engineering safety
Soil disintegration did not occur in the process of water loss, but in the process of water absorption. e drying degree of soil mass had a great influence on the disintegration degree of soil mass [13]
Chen proposed that the main cause of soil mass disintegration was water absorption expansion of minerals, which resulted in compression of air and generated tensile stress. en, the stress concentration resulted in soil mass collapse due to differential expansion [15]
Summary
3.1. Test Description. e test water tank was made of transparent acrylic to facilitate the observation of the sample disintegration process, as shown in Figure 2. A scale was set outside the side wall of the model box to observe the sample depth. e water was added to the tank to 55 cm depth, and the prepared sample and the wire mesh tray were put into the water to the predetermined depth. e wire mesh tray was hung on the dynamometer hook through the four-angle sling. e depth of the sample from the water surface was 18 cm, 30 cm, and 42 cm, respectively. e data every half minute was recorded until the soil sample disintegrates completely. Repeat the above test steps until all tests were completed. 3.2. Test Results. e disintegration curve of the same volume samples in different water depth is shown in Figure 3. It can be seen from Figure 3 that the deeper the position was, the shorter the disintegration time was under the same initial conditions. e disintegration time of the sample is the longest at the water depth of 18 cm and the shortest at the water depth of 42 mm. It also can be seen that, in the process of sample disintegration, the rate of sample disintegration in the early and later stages of the disintegration test was relatively small, and the rate of sample disintegration in the middle stage was relatively large. e disintegration residual mass curve of the soil samples with the same volume and different shape at different water depth is shown in Figure 4. It can be seen from the curve in Figure 4 that the disintegration rate of quadrangular specimen was faster than that of cylinder specimen in the early stage of sample disintegration, but the disintegration rate of quadrangular specimen was slower than that of cylinder specimen in the later stage. e disintegration residual mass curve of the cylinder soil samples with the same volume and different diameter at different water depth is shown in Figure 5. It can be seen from the curve in Figure 5 that the disintegration time of the thin cylinder soil sample is longer than that of the thick and short cylinder soil sample under the same volume and water Name Water content w (%) Unit weight c (kN/m3) Specific gravity Gs Plastic limit WP (%) Liquid limit WL (%) Plasticity index IP (b) Figure 1: Soil samples, (a) cylinder samples, (b) quadrangular prism samples.
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