| With the development of human engineering activities in recent years, landslides pose many serious threats to agricultural production and people’s lives and properties, or even a devastating disaster. Mount Gaolan landslide III is located in the east of Mount Gaolan, belonging to key prevention area of geological disaster in Lanzhou. The biggest length along the sliding direction of the landslide is700m, and the total volume is about1100×104m3, so it is an oversize landslide. Lives and properties safety of1213households and teachers and students of a school around the landslide are threatened. It is based on reasons above mentioned that I conduct related research on Mount Gaolan landslide III.I make a detailed analysis on geological environment background, characteristics, cause of formation and influence factors of stability in this paper. On this basis, I analyze and calculate the stability of Mount Gaolan landslide Ⅲ. The stability analysis is based on qualitative assessment of field geological survey results, and the stability calculation is achieved by residual sliding force method and numerical simulation analysis method FLAC3D. Finally, I make a comprehensive evaluation of landslide stability and use AHP (analytic hierarchy process) to obtain the optimal solution. The main contents and conclusions are as follows:(1) After analyzing the geological background and causes of the landslide formation, I think that this landslide belongs to local reactivation of an old landslide, and the main sliding body is the old landslide accumulation (including loess-like silt and full strongly weathered mudstone layer). A higher moisture content soft zone exists in old landslide. When a storm or green irrigation water happens, water directly infiltrates through the vertical joints, cracks, sinkholes and other natural channels. Bedrock is regarded as relative impermeable layer to form a smooth seepage surface locally, which provides the landslide with "lubricant". Besides, excavation and disturbance of human engineering activities on the slope will reduce the slope stability.(2) According to field judgment analysis of the landslide stability, there are a larger free face on leading edge of slope, many new cracks and gullies on the slope, stagnant zones which could make soil soft and are more likely to produce creep deformation among the slide zone, so the landslide may cause instability in the conditions of storm or earthquake.(3) On the basis of stability analysis above, combined with experimental data, I calculate landslide stability further by residual sliding force method. The results as follows:①the landslide is in a stable state under natural conditions;②it is in less stable state in the condition of storm;③it is in less stable state in the condition of earthquake. The stability of profile3-3corresponding to the slider is the worst, and it is the most dangerous landslide in four parts, belonging to the potential landslide.(4) Using FLAC3D to make three-dimensional numerical simulation of3-3potential landslide, obtain stability safety factors of the landslide, the size of horizontal displacement, shear strain increment distribution, and the stability coefficient of slope under three kinds of conditions is slightly larger than the calculation results under the residual sliding force method, but the conclusion of two methods is consistent. At the same time, according to the distribution of displacement size and shear strain increment, I determine further this landslide belongs to an old traction landslide, and landslide deformation modes are creeping, cracking and drawing.(5) On the basis of stability evaluation, according to comprehensive factors which including engineering geological characteristics, size of residual sliding force, environment and so on, I put forward to possible treatment measures and obtain the optimal solution by using AHP. |
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