Study On Deformation Mechanism Of Landslide And Optimization Of Anti-slide Retaining Design Under Complex Moving Path

Many landslides in nature are affected by the undulating terrain and sliding surface morphology,and they will show complex behaviors such as turning,splitting,coalescence,and braiding during the movement process,and these behaviors are common.The study of the deformation mechanism of landslide under complex moving path is helpful to assess landslide risks and take reasonable support measures,which is of great significance to the prevention and mitigation of geological disaster.In this thesis,the Pangjiawan landslide,which has turning and coalescence behaviors,is taken as the research object.On the basis of detailed field investigation and indoor geotechnical test,combined with the three-dimensional geological model,the numerical analysis model of the landslide is built by using the three-dimensional particle flow code PFC3 D,which simulates the deformation and failure process of the landslide,and analyzes its deformation mechanism.Aiming at the Pangjiawan landslide with complex moving path,an optimized design scheme of anti-slide piles is proposed,that is,anti-slide piles are arranged in arc shape on the plane,and PFC3 D model of anti-slide retaining structure is established.The deformation characteristics of landslide supported by the optimized design scheme are simulated and analyzed,and compared with the simulation results of the original retaining structure scheme.The main work contents and achievements are as follows:(1)By analyzing the engineering geological conditions,spatial form,material composition and deformation characteristics of the Pangjiawan landslide,it is shown that the landslide has complex moving paths.The sliding soil is mainly silty clay,the upper sliding direction of the landslide is 63°,and the lower sliding direction is 104°.(2)The Pangjiawan landslide model with complex terrain is built by using topographic contour,section map and borehole data,combined with three-dimensional geological modeling technology.The boundary of sliding body and sliding bed is determined,and the model is imported into PFC3 D software.The adhesive rolling resistance linear model was configured for the particles to simulate silty clay,and the meso-mechanical parameters of soil are calibrated through the PFC3 D direct shear numerical test,and then the particle flow calculation model of the Pangjiawan landslide is generated by the ball-wall method.(3)Simulate the movement process of the Pangjiawan landslide,and analyze its deformation and failure mechanism.The simulation results show that the total time from starting to accumulation is about 504 s,and the landslide movement has turning and coalescence behaviors.The soil on the turning movement path first begins to slip and deform,and the movement direction deflects by 41°.However,the soil deformation in the northeast area in the front of the landslide is slow and small,so the landslide deformation is uneven.The landslide reaches its maximum speed at 40 s,and then starts to decelerate.The kinetic energy of the landslide gradually decreased,and the energy dissipated by friction and sliding accumulates with time.When the landslide movement stops,a large amount of soil is sheared out and accumulates at the foot of the slope.(4)The retaining effect of the original anti-slide retaining scheme on the landslide is studied by PFC3 D software.The simulation results show that the original scheme hinders the overall deformation and failure of the landslide,but the soil particles in the front of the landslide move downward at a small speed,and small deformation occurs locally in the landslide.The anti-slide piles set at the foot of the slope are subjected to the thrust of the landslide in different directions,and there is soil slip between anti-slide piles.The complexity of the landslide moving paths is not considered in the original retaining design,so the anti-slide piles should be optimized.(5)The optimized design scheme of supporting landslide with arc-row anti-slide piles is proposed,and the supporting effect of arc-row anti-slide piles with different risespan ratios and different numbers is simulated and analyzed.It is found that the larger the rise-span ratio is,the better the retaining effect is.When the rise-span ratio is 0.1,the landslide has almost no deformation.When the arc-row anti-slide piles are adopted,one or two anti-slide piles are reduced on the basis of the original design,which has little influence on the landslide deformation.By comparing the original anti-slide retaining scheme with the optimized design scheme,it can be seen that the retaining scheme of arcrow anti-slide piles can reduce the movement speed and displacement of the landslide,and the soil behind the piles occurs soil arching.The optimized design scheme has a good effect on the landslide support under complex moving path.