The Study On Failure Mechanism And Control Measures Of Loess Landslide Of Baita Mountain

The thesis takes the loess landslide of Baita mountain in Lanzhou city as the project background to study the failure mechanism of loess landslide and remediation technology.By consulting many relevant literatures,the features of loess and the origin,classification of landslide were summarized and analyzed at first;Second,the triggers and deformation behavior of landslide in loess area were summarized by combining the research status both at home and abroad;Third,the occurrence mechanism and regulation measures of loess landslide in beilin in great detail were studied depend on some basic physical property tests,triaxial shear test,model test,analysis of numerical simulation and the relevant dates.The main conclusions are as follows:(1)The factors that affect the stability of loess slope include landform,geological conditions and some extraneous factors like rainfall infiltration,earthquake,freeze-thaw,human activities and so on.The prevention and control of the loess landslide should be combined with the local conditions,taking into account the internal and external factors,eliminating the influence of the water,and adopting the reasonable supporting scheme.(2)Based on the soil samples collected in the field,the density test and moisture content test with undisturbed soil,the compaction test with disturbed soil and triaxial shear test with manipulated soil were completed.The results of tests indicates that the average density of soil is 1.47g/cm3,the average moisture content of soil is 3.9%,the maximum dry density is 1.83g/cm3,the optimum moisture content is 16.4%,The cohesion and the angle of internal friction of soil samples change accordingly with the change of rate of water content.(3)In the model test of indoor rainfall,the infiltration rate of rainwater decreases gradually and tends to be stable from the beginning to the end,The permeability of soil decreases from unsaturated to water saturated,and the decrease of matric suction results in the decrease of infiltration rate.In the process of rainfall,the total infiltration of slope is that water infiltrate faster on the top of slope than incline,the moisture content of slope's surface continue to increase until close to saturation,then,water infiltrate into inside of the slope gradually.When monitoring the pore water pressure of three points along the shallow part of slope,it increases to a peak value and then moves up and down in a certain range,at the time of 150 minutes and 350 minutes,the pore water pressure in the middle part of the slope is obviously reduced,and the soil is destroyed to some extent.From the beginning of rainfall to the end of large-scale landslides,the whole process is divided into three stages,that is,the formation of the cracks,the formation of the sliding body and the creep damage.(4)The safety factor of the slope is 1.028 in a natural state and 0.937 under long-term rainfall and irrigation by using the method of limit equilibrium to analyse the stability of slope which called H-1,both of them are instable.Using FLAC 3D to simulate the stability of slope,the safety factor of slope under natural condition is 1.52 with anti-slide pile and 1.04 without it;The safety factor of slope under long term rainfall and irrigation conditions are 1.37 with anti-slide pile and 0.95 without it.