Research On The Disaster-causing Mechanism Of Dujiashan Landslide

Dujiashan landslide is located on leftside of the dongdu river, belonged toDujiashangroup of Xiejiaping village in Lueyang county. Lueyang county is located in the southwestof Shaanxi Province, belonged to Qinba mountainous area.With many steep slopes and deepvalleys,geological disasters frequently occur. Dujiashan landslide is the larger one in scaleand risk, and has a certain degree of complexity and representation in landslide hazards ofLueyang county. Based on this situation,taking Lueyang county as the background,this thesistakes typical Dujiashan landslide as the research object to comprehensivly analyze theinfluence factors, formation mechanism, stability, and destruction of landslide,so as to providereferences for stability evaluation and disaster prevention and reduction of similar landslidesin the regions. The main research contents and the results obtained of the thesis are as follows:(1)Through field investigation, landslide deformation monitoring and landslideinvestigation, the main characteristics of Dujiashan landslide is identified. According to itsmorphological characteristics and deformation characteristics, Dujiashan landslide is dividedinto three sub zones. Its main predisposing factors and formation mechanism are analyzedalso. Research shows that Dujiashan landslide is a large accumulation layers landslide,whichslides along the rock and soil contact surface. Research also shows that rainfall is the mainpredisposing factors of landslide and the Collapsing-sliding load of trailing edge is the mainlandslide mechanics mechanism. With upper sliding body’s cumulative load, the upper soilslides ceaselessly. This promotes the formation of sliding-pushing body, which has a effect ofheaped load on the lower sliding body and a degree traction effect on the upper sliding body.(2) Using natural history analysis method, finite element method, limit equilibriummethod, this thesis systematically analyzes the deformation and stability of landslide onnatural condition, rainfall condition,and earthquake condition. Analysis shows that theDujiashan landslide under the natural condition is stable, but under rainfall or earthquakecondition the landslide is on the state of limit equilibrium. Especially under the condition ofheavy rain, the stability of landslide decreases substantially and is not up to the safetyrequirements, showing that rainfall has significant effects on the stability of landslide. Theseconclusions are consistent with the real situation.(3) The thesis assesses the risk of Dujiashan landslide. Using estimation methods ofsliding speed and distance, the thesis analyzes the hazard scope of landslide.The calculatedmaximum sliding speed is42.15m/s.The calculated maximum sliding distance is904m. Thelandslide hazard scope is about2.49×105m2. The thesis also analyzes the formation mechanism of the blocked lake caused by landslide and the height of weir dam. Predicted damheight is up to54.27m. Weir dam area is about5.4×104m2.Its volume is about2.93×106m3.Based on the analysis above, the thesis predicts the loss of lives and property caused bydisaster and the conclusion is that the landslide loss grade is big grade. Combined with thelandslide stability in unfavorable conditions, the thesis divides landslide possibility into thebig stage. According to the possibility and loss of landslide, the landslide risk grade is dividedinto big grade.