| There is arid and semi-arid climatic zone in Loess Area, for the needs of agricultural development and the people’s lives, since the 1970 s, they built a large number of irrigation water project. Irrigation makes natural geological conditions of different degrees of change in irrigated areas, also the Ecology is destroyed. Since 1976 irrigation, there are frequent landslides disasters, not only caused a lot of casualties and property losses, but also makes the continual loss of valuable land resources, Also the development of local social economy was restricted. Thus forming mechanism of irrigation-induced type landslide and the breeding process will be very theoretical and practical value. In this paper, based on the field investigations, physical and mechanical tests, field trials, laboratory experiments and numerical simulation and other means, we researched the development of the whole process and discuss its stability and failure mechanism of the irrigated landslide. The main results of the research are as follows:⑴ By the Situ water seepage test, we get all kinds of saturated hydraulic conductivity of soil and the horizontal and vertical changes in moisture content by the test soil profile. The results show that the process of infiltration that is transient saturated zone continues to expand. By the triaxial permeability test measured the vertical and horizontal directions saturated hydraulic conductivity under confining pressure, the results identify that with the increase of confining pressure the horizontal and vertical to the saturated hydraulic conductivity was reduced regularity and anisotropy gradually disappear. The permeability coefficient of the paleosol is so small that as aquifuge.⑵ By the SWCC test measured each soil desorption curves, According to the results of tests in situ seepage, we use software to simulate the seepage inversion process and get all the relevant parameters of soil moisture curve. Using the Mualem model to estimated the unsaturated soil hydraulic conductivity, analyzed and compared the difference between desorption and moisture Absorption process. The results showed that there was a big difference in permeability between desorption and moisture Absorption process, the soil Permeable will be affected by matrix suction and water content.⑶ Simulated the seepage field under irrigation action, analyzed the situation of increased groundwater in 25 years and the variation of the pore water pressure in the slope. On this basis, when we analysis the slope stability we parted it in two situation that are considering matric suction and does not consider matrix suction, the results showed that when considering the matric suction is greater than is not considered a matrix suction in safety factor. Continuous analysis of slope stability for 25 years and to draw a relationship between the safety factor and time, the safety factor begins to decrease rapidly from the thirteenth year, until the safety factor of the second decade began to stabilize. It can be seen that from the beginning to the irrigation landslide is a long process.⑷ Landslide mechanism obtained through experiments and numerical simulation, The main process is: Groundwater rise—The increase thickness of the saturated loess—Strength reduce and Squirming—The trailing edge of a crack occurs also saturated loess liquefaction at the same time—Landslide occurred.⑸ By orthogonal test, Analyzed the effect of three factors friction angle、cohesion c、 the friction angle that corresponding to the suction on slope stability, the results show: friction angle has a significant effect on slope stability, while cohesion and friction angle suction have no significant effect on the result. |
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