Study On The Motion Feature Of The Collapsing Rockfall Based On 3D Terrain Visualization

The Tianshan highway is located in the area with high cold and high altitude and the geological disasters along its line have many characteristics,such as large quantity,wide area,small scale,strong explosiveness and serious harm.However,at the same time,the research area is mostly in the high and steep position,so the general research methods are difficult to implement and some data which directly affects the research results,are difficult to obtain or obtain inaccurately.In fact,with the development of economy and society,the Tianshan highway is playing an increasingly important role.Therefore,it’s also becoming increasingly urgent to study the collapsing rockfall along its line.This paper,using two non-contact measurements,3D laser scanning technology and close shot photogrammetry technology,obtains the 3D terrain data and uses these data to attain the multi-platform mode 3D terrain visualization.On the basis of that,it studies the stability,the motion feature and risk of the collapsing rockfall,and in the end,it studies the whole process of instability of the collapsing rockfall by using discrete element numerical simulation software 3DEC.Through the above research,the main achievements are as follows:(1)The data,attained from the 3D laser scanning technology and close shot photogrammetry technology,are transformed into the models which are suitable for different platforms including virtual reality modeling,3D browser model and 3D-printed entity model.It attains the multi-platform mode 3D terrain visualization.(2)The stability of unstable rockmass in the study area is analyzed by using the high precision points cloud data of the highway slope and respectively using stereographic projection evaluation theory and limit equilibrium theory.It is found that the unstable rockmass 1 is easy to produce the slipping failure mode of the rockmass and the unstable rockmass 2 is easy to produce the dumping failure mode of the rockmass.Under four different conditions which are deadweight,deadweight and rainstorm,deadweight and earthquake,and deadweight and ice bulging force,it is found that k632 the slipping failure mode of the rockmass is easy to be unstable and destroyed under the earthquake,and k632 the dumping failure mode of the rockmass is easy to be unstable and destroyed under the rainstorm.(3)Based on the accurate points cloud data and the rockfall kinematics calculation theory,the motion features of unstable rockmass are analyzed.And the conclusions are as follows.Firstly,the slope micro geomorphology has a great influence on the motion process of rockfall.Gravelly soil has an obvious effect to dissipate the energy,while colluvial stone has a non-obvious effect to dissipate the energy.Secondly,the projectile effects of earthquake make stone have higher kinetic energy and the hazard area also becomes bigger.Thirdly,the motion process of rockfall can basically be divided into three stages: initial displacement,collision and jumping,and rolling.(4)Combined with 3d laser scanning data and field investigation results,it evaluates the risk of rockfall of k632 the unstable rockmass 1.By considering the annual probability of rockfall,the arrival probability of falling stone,the space-time distribution characteristics of bearing body and the vulnerability data of the bearing body,the risk of individual unstable rockmass is analyzed.Through the calculation,the risk value of rockmass in the study area is higher than that of the social tolerance standard,so it is the unstable rockmass which needs to be administered.(5)Point cloud of the k632 slope which is obtained from 3D laser scanning technology is transformed into a discrete element model with accurate slope information and structural surface information.On this basis,numerical simulation is made through 3DEC.Through the simulation calculation,under the effect of seismic dynamic loading,the trailing edge of the slope will firstly form cracks along the surface.Along with the change of seismic dynamic loading,cracks continue to open and form run-through.The bottom of the whole unstable block moves in sliding mode.The upper part is affected by the effect of seismic ejection,and it moves in the form of collision and jumping.Finally,along the motion trail of rockfall,some pieces of stones accumulate on the road,while the other part jump deeper into the road.The simulation shows that under the effect of seismic dynamic loading,if the rockmass becomes unstable,it will have a great impact on highway operation.