Study On Development And Distribution Characteristics Of Collapse And Rockfall Movement Process In Changdu Section Of Proposed Line Project

Along the Proposed line project,the terrain is high and steep,the geological structure is developed,the valley is deep,the climate environment is bad,and the collapse and dangerous rock disasters are very developed,which seriously threaten the construction and operation safety of the proposed traffic engineering.It is of great practical significance to study the distribution characteristics of rockfall and rockfall movement process for ensuring engineering safety.At present,most of the analysis methods at home and abroad assume that the rockfall slope is a rigid underlying surface,so as to calculate the running distance of rockfall.However,the actual situation is not all rigid.The surface of rolling stone movement slope is often covered with loose accumulation layer,and the stiffness towards the slope body increases gradually.The non rigid surface of surface layer will lead to energy dissipation of rolling stone and affect its motion state.For the process of rockfall movement,it is difficult to analyze and calculate due to the influence of rockfall characteristics and topographical and geological conditions,which is also a hot and difficult point in the field of geological engineering at home and abroad.Based on this,combined with the actual project,on the basis of data collection and field investigation,through remote sensing interpretation,UAV photogrammetry,geological mapping and verification,numerical simulation,theoretical derivation and other means and methods,this paper analyzes the development and distribution characteristics and instability failure mode of rockfall along the project,establishes a numerical model to simulate and analyze the rockfall on the non rigid slope The calculation method of the moving distance of rockfall is discussed.The main research results are as follows:(1)Through remote sensing interpretation,UAV photogrammetry and field investigation,the development of geological disasters in the first slope zone along the Changdu section of Proposed line project is identified.There are 882 collapse dangerous rocks,27 landslides and 29 debris flows along the project.The collapse dangerous rock is the most developed,the two ends of the project line are the most developed,and the middle part is relatively less,which is one of the main geological disasters affecting the safety of the proposed project.(2)Through geological mapping and UAV photogrammetry interpretation,the development and distribution characteristics and instability movement mode of collapse dangerous rock along the project are analyzed and revealed.In terms of stratum lithology,collapse dangerous rock mass is the most developed and dense in granite area;at altitude,collapse dangerous rock mass is most developed in 3400 ? 3600 m altitude.The results show that the number of collapse dangerous rock mass decreases with the increase of altitude above 3900m;on the slope,the collapse dangerous rock mass is most developed in the range of 30 ° to 40 ° slope;in the slope direction,the development density of collapse dangerous rock mass is more developed than that towards the downstream;in the range of 0 ? 2km,the development of collapse dangerous rock mass is negatively correlated with the distance from fault;on the slope structure,the bottom structure of collapse dangerous rock mass is developed,the closer the inclination and dip angle between the surface and the slope,the closer the dip angle of the structural planes on both sides of the dangerous rock mass,the more developed the dangerous rock mass of slope collapse.There are three typical instability modes of collapse dangerous rock in the study area: sliding,rolling and falling.(3)The calculation methods of normal and tangential recovery coefficient of rockfall impact on non rigid slope are proposed.Considering the falling height of rockfall,different shape of rockfall,thickness of loose soil layer,slope gradient and size of rockfall,the impact of rockfall on rockfall rebound is simulated by ABAQUS software.On the basis of five factors,the new calculation method is compared and analyzed.(1)The collision process of rockfall and non rigid slope is divided into three stages: free fall,compaction of loose soil layer and rebound.According to the principle of kinematics and dynamics,combined with the existing formula of maximum impact force,the calculation formula of impact recovery coefficient of rockfall on non rigid slope is derived.(2)In ABAQUS simulation analysis,the coefficient of restitution has different response to different factors.The results show that the impact recovery coefficient is not affected by the falling height of rockfall;in the shape of rockfall,the impact recovery coefficient of prism,sphere and cube decreases in turn;the impact recovery coefficient decreases with the increase of the thickness of loose soil layer;the normal collision recovery coefficient is not affected by the change of slope,The recovery coefficient of tangential impact increases with the increase of slope gradient,and there is no obvious linear relationship between normal collision coefficient and rolling stone size.(3)The new calculation method,the existing calculation method and the numerical simulation method are compared and analyzed.The results show that the calculation results of the new method are more consistent with the numerical simulation results than the existing methods,and more consistent with the actual situation.(4)According to the three modes of rockfall instability movement: sliding,rolling and falling,a new calculation method of rockfall motion distance based on new collision recovery coefficient is analyzed and deduced.Combined with the engineering case,the analysis application and error analysis evaluation are carried out.The results show the error between the calculated moving distance and the actual moving distance is smaller than the assumed rigid slope,which is more in line with the actual situation of the project.