|Alternative Title||Seepage-stress Coupling Mechanism and Application in Loess Slope Landslide|
|Place of Conferral||北京|
Loess in China is widely distributed, especially in the Loess Plateau such as Gansu, Ningxia, Shaanxi, and Shanxi in the middle reaches of the Yellow River. It is one of the regions with the most serious soil erosion and the most ecological environment in the world. In the case of continuous rainfall or sudden downpour or large-scale irrigation, landslide disasters occur frequently, causing serious disasters, posing a great threat to the lives and property of local people. This paper studies the formation, occurrence and development of the landslide hazard of the loess slope and the coupling mechanism of water and soil, aiming to provide a scientific basis for the prevention and control of landslide disasters in this area.
In this paper, the slope stability analysis model under seepage condition is established firstly. The Yangjialing landslide is numerically simulated by finite element strength reduction method, and compared with the traditional method, the reliability of the model is verified. Taking the severe landslide caused by sudden rainstorm in Yulin, Shaanxi Province in late July 2017 as an example, the variation of different rainfall processes and the stability of slope after considering the weakening effect of water on soil were analyzed. Based on the irrigation project in Heifangtai area of Gansu Province in 1969, the numerical simulation of the 10-year irrigation period was carried out, and the optimal drainage hole length setting was analyzed. A preliminary discussion on scientific irrigation methods for local crops. The main findings of the thesis research are as follows:
According to the case of Yulin landslide in Shaanxi, the effects of different rainfall intensity and duration on the stability of loess slope are analyzed. It is found that the rain on the loess soil slope will infiltrate rapidly, resulting in a sudden increase in pore water pressure and a decrease in slope stability. The rate of decline of the safety factor is slower and slower. This is due to the fact that the loess structure is thick and vertical, and the crack is rich. The simulation results also show that the greater the initial water content of the soil, the lower the stability of the slope, and the more likely the landslide disaster occurs.
A large number of experiments have proved that the soil water content can reduce the soil shear strength (including cohesion and friction angle), so the water and soil coupling must consider the weakening effect of water on the soil strength. We have found that the weakening of the soil strength directly leads to a further decline in the stability of the slope. The effect of the soil's cohesion is more obvious than the soil friction angle.
The simulation of the seepage inside the slope under the condition of flood irrigation in the Heifangtai area shows that the slope is in a stable state before the irrigation water reaches the groundwater level. When the infiltration front reaches the groundwater level, the irrigation water in the slope body replenishing the groundwater level will cause the groundwater level to rise rapidly, thus reducing the stability of the slope and easily causing landslide disasters.
In order to prevent loess landslide caused by irrigation, the drainage method can be used to obtain obvious effects, which is economical and practical. For practical engineering cases, the length of the drain hole is best at setting an optimum value. At the same time, we also carry out scientific irrigation simulation according to the local ecological environment and crop demand, so as to achieve the purpose of preventing landslides and saving water.
|周丹洋. 黄土坡体滑坡水土耦合机理及其应用研究[D]. 北京. 中国科学院大学,2019.|
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