| Landslide disaster has now become the main geological disaster in our country, this kind of disaster can cause clogging rivers, buried the village, and to destroy factories, also to interrupt the traffic situation, which causing great economic losses and casualties. While rain, especial strong torrential rain, is the most important factor to promote landslide. According to statistics, landslides induced by rainfall is distribution of a wide range in the world, and the frequency is quite high, its harm is quite serious, in addition, a large number of statistical data also shows that a large part of the landslide occurred in the process of rainfall or after a period of time after the rain. Understanding the mechanism of landslides which rainfall induced has long been a difficult work of the studies on the mountain disaster, at the same time, also restricting the disaster early warning and forecasting work and the bottleneck of effective prevention and control. In this paper, the rainfall infiltration conditions of loose soil landslide are studied, as a reference of disaster prevention and control work has important realistic mean. In order to get the goal, research methods are adopted in this paper based on Soil water characteristic curve button box test, indoor soil column model rainfall experiment, to explore research permeability of loose soil landslide in the rainfall.The paper on the each channel of qingping township affected by the "5.12" Wenchuan earthquake, at the scene of the landslide disaster investigation, find out and analyze the precipitation condition, neotectonic movement and earthquake, human engineering activities, landform and so on. Through investigating Wenjia gully way at the spot and the representative sample, it gives some general indicators, such as compactness, water content, content of clay and other specific parameters, which performacing Wenjia gully landslide well.Through organizing that field geological information, at the same time, in order to clear the contents of the study, namely, in rainfall, the permeability of loose deposit and in the process of osmosis, the change of a series of parameters such as soil moisture content and matrix suction and pore water pressure, etc, in addition, different initial moisture content and different compactness of pile soil show the settlement rule in the same rainfall condition. In this paper, engaging in two types of indoor test: soil water characteristic curve button box test, the large rainfall indoor soil column experiment, finally, got the following results and understand.(1) Infiltration line is not a horizontal line in different initial moisture content and different compactness states at the stage of rainfall, but present angle of non-uniform infiltration. The tilt direction of infiltration line is random change with the increase of infiltration depth.(2) At the stage of rainfall, the tilt direction of infiltration line has a certain randomness. And it is concluded that the moisture content change rule is: increase from the top to the bottom of soil in rainfall infiltration, and the top is rapidly maturing. Firstly, the surface of soil begin to infiltration in the rain, further the central to be saturated, finally, when rainwater infiltration to the bottom of soil, the moisture content distribution of the loose deposit is to be a basic stable condition.(3) By monitoring the matrix suction and moisture content, find a relation between rainfall infiltration velocity and the initial soil moisture content, which suggests that within a certain range of initial moisture content, the greater the initial moisture content of soil at the same other conditions, the bigger the seepage velocity in the soil.(4) Different initial state of loose accumulation soil, at the same rainfall condition, its subsidence and sedimentation rate are analyzed, showing that within a certain range of initial soil moisture content, the subsidence of soil obviously happened, and the greater the initial moisture content of soil, the greater sedimentation velocity, but its ultimate settlement amount is smaller, explained by its three phase of clay.(5) The changes of the pore pressure in the process of rainfall infiltration were monitored, and the change of the pore pressure was analyzed. The change of pore water pressure is divided into four stages, namely, no obvious change stage, fast rising stage, slowly rising stage and relatively stable stage. This change characteristics are corresponding to the rainfall infiltration: no obvious changes and rapidly rising phase in pore pressure corresponds to the pressureless infiltration stage of the rainfall and the pore pressure slowly rising stage corresponds to the rainfall pressure infiltration stage, and the pore pressure in a relatively stable state phase corresponds to the saturation infiltration stage of rainfall.(6) By the soil water characteristic curve box test, the soil water characteristic curve is obtained in different compactness and moisture content. the analytical results show that with the constant improvement of the degree of loose accumulation soils water, the matrix suction is reduced gradually, and when the moisture content is within 0% to 6%, with the increase of moisture content, the matrix suction decreases quickly, but when the moisture content is more than 6%, with the increase of moisture content, the falling speed of matrix suction will drastically reduce. Soil, in the case of other consistent conditions, the more denser, the greater the matrix suction, and when the moisture content is 0% to 8%, it is obvious especially, while, with the increase of soil moisture content, the size difference of soil matrix suction of different compactness is not obvious. |
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