Dynamic Characteristics Analysis Of The Wenjiagou Rock Avalanche

Rock avalanche is a kind of devastating geological hazard,which is always sudden,rapid and with a long run-out.It is quite important to study the triggering factors,mechanisms causing high speed and long distance and characteristics of motion and deposition.Because of its infrequence and emergent property,as well as the lack of the monitoring data in situ,it will be very difficult for investigators to determine lots of parameters when they try to solve the problem using theoretical formulas or to simulate the movement process of rapid landslides.Laboratory experiment can provide some basic parameters for simulations and overcome the shortage of simulation.Factors which affect the kinematic process and deposition characteristics of rock avalanche are studied by experiments and numerical simulation.The Wenjiagou rock avalanche is reproduced by numerical simulation with PFC3 D.The following shows the main work and results.(1)Materials,diameters of grains,slope,volume,releasing time and geometry used for testing of grains flowing down typical slide bed has been varied and their influence on the movement process and deposit characteristics is studied by experiments in laboratory.The results show that the extent of scree is wider than gravel,the effect of releasing geometry and slope is not obvious,while the increase of volume and releasing time can decrease the run-out.(2)Relationship between micro parameters for numerical simulation and deposit characteristics is set up by BP neural network using the results of uniform design experiments,then the micro parameters for the simulation of lab experiments is determined by back analysis using the trained network,as a guideto the simulation of the rock avalanche on earth.(3)Numerical simulation model for Wengjiagou is built based on the geological characters and primary analysis of its mechanism to reproduceits movement process,then effect of different friction of slope,parallel contact strength and stiffness on the movement and deposit are studied.Best fitting parameters are a friction coefficient of each slip surface equal to 0.2,parallel bond strength of 2Mpa and contact stiffness of 2e8 k N/m.It takes about 115 s for most grains to stop moving from onset,the maximum velocity reaches 114m/s.Most grains deposit in Wenjiagou valley due to decrease of moving ability because of three times dramatic conflicts with the mountains.