| The Nujiang River originates from the Jirepage at the southern foot of Tanggula Mountain on the Qinghai-Tibet Plateau.The section from Jiayu Bridge in Luolong County to Lushui County in Yunnan Province in the middle reaches belongs to the Hengduan Mountains..It is a typical alpine and canyon landform with active tectonics,which causes frequent occurrence of landslide disasters and some other secondary disasters.As national strategic large-scale engineering projects(railroads,highways,hydropower projects,etc.)advance to the Nujiang River basin.It is necessary to study the genetics mechanism and kinetic characteristics of the large-scale damming landslide.The giant damming landslide in Qianjin village is located in Chawalong Township,Chayu County,in the southeast of Tibet Autonomous Region,in the northern section of the Hengduan Mountains.in the northern section of the Hengduan Mountains of the Qinghai-Tibet Plateau.It is a rare block of one river and two banks,and the accumulation of damming landslide is composed of granite landslide accumulation on the left bank and schist landslide accumulation on the right bank.Revealing the cause mechanism and movement characteristics of the blocking river landslide can provide technical support for regional disaster prevention and mitigation.This thesis takes the Qianjin village large-scale damming landslide in the Nujiang River basin as the research object,adopts a combination of engineering geological mechanism analysis and numerical simulation quantitative analysis.Through geological investigation and data collection,the engineering geological conditions of the landslide area are clarified,the deformation and failure mechanism are revealed,and the landslide engineering geological models are established.On this basis,discrete element numerical simulation is carried out to analyze the cumulative failure,the dynamics-induced mechanism and the process of blocking.Through the systematic study of Qianjin village landslide,main research contents and results of this paper are as follows:(1)The study area is located in the Nujiang Basin of Three-rivers basin in the Hengduan Mountains.The structural conditions are controlled by the Nujiang structural belt.The terrain is steep and the geological structure is strong.The synergy of internal and external dynamics strongly controls the incubation of large-scale landslides.The landslide dam in the valley is composed of the Gedui village landslide on the right bank and Qianjin village landslide on the left bank.The effect of blocking mainly comes from the landslide in Qianjin Village on the left bank.(2)The Gedui village landslide on the right bank has a layered structure within a schistal steeply inclined slope(the occurrence is 250-270°∠68-75°).Due to river valley erosion and unloading,interlayer dislocation and rock formations are bent,causing deep layers dumping gravity deformation.At the same time,the crushing shear zone produced by the self-weight load of the deep deformed body provides the weak structural plane.As the river continues to cut down and the dumping deformation amplitude increases,eventually the rock mass on the right bank slope reaches the limit of shear strength and begins to slide...(3)The strength of the granite rock mass in the source area of Qianjin village landslide on the left bank is very high.However,there are many groups of structural planes caused by regional active tectonics developed inside the slope,among which three groups of main structural planes(J1,J2,J3),their occurrences are 232° ∠34°,246°∠78°,311°∠68°.The three groups of structural planes constitute the bottom fracture surface,the back wall,and the lateral boundary.The joint cutting of the rock mass provides the possibility of failure and slippage of the slope.Eventually,it is triggered by strong vibration conditions and slips into the valley to form a giant damming landslide.(4)Through the discrete element software UDEC,the developmental mechanism and kinematic mechanism of Gedui village landslide and Qianjin village landslide are numerically simulated,and the results show that the failure mode of the Gedui village landslide is dumping-bending-slip.During the process of deformation accumulation and failure,the displacement showed a decreasing trend from outside to inside,and it is judged that it is a landslide developed by the gravitational deformation of the weaker mica schist.The body of Qianjin village landslide is a high-strength granite,which has good stability in its natural state.It is broken under the control of the earthquake action and the structural plane,and then slides down to form a giant damming landslide.(5)By simulating the movement process of Qianjin village landslide,it can be obtained that the sliding body has experienced four stages of acceleration,deceleration and climbing,reverse acceleration,and self-stabilization.The maximum speed of the slide during acceleration is 62m/s,and the maximum speed during the reverse acceleration process after climbing is 22m/s.Finally,the left bank accumulation partially stops on the right bank,with a maximum horizontal distance of 1200 m and a minimum horizontal distance of 790 m.It shows that the Qianjin village landslide is induced by the dynamic action of earthquakes.Under the control of the high potential energy of the deep-cut valley,the granite sliding body slides at a high speed,and finally hits the Gedui village landslide deposit on the right bank,causing a huge river blocking effect. |
