Study On The Interaction Of Rockfall And Soil Layer

In China, the unstable rock disasters occur in steep mountainous areas frequently, which often cause road traffic blocking or traffic accidents, and have a significant impact on road and railway construction and operation, but also cause people in the mountain great casualties and property losses. Rockfall hitting the ground impact is based primarily on when designing shed tunnels, cut-and-cover tunnels and passive protection structures. However, currently the effect of buffer layer on intercepting the rockfall was not very well, sometimes injuring people. Therefore, it is important to study on the response of rockfall impacting buffer layer.This article analyzed the geological conditions of rockfall, factors causing rockfall hazards and the movement pattern of rockfall. It summarized previous research on rockfall hit, and basing on a simplified model, combining with the ABAQUS finite element analysis software, simulated the impact conditions of rockfall of different weight and height with the buffer layer of different thickness. With the impact force data calculated, it found the effect of relevant factors to rockfall impact force, studied propagation of impact force and buffer mechanism of soil, proposed a more realistic approach to calculate impact force. Comparing new algorithm with the existing calculation methods, we verified its practicality.In addition, it simulated collision and bounce motion of rockfall, analyzed the process of declining and bounce after rockfall collision. Given the soil cohesive stress young’s modulus, soil thickness were respectively treated as variable, it analyzed their influence on the declining depth, rebound height and impact force, got the relation of them and the declining depth, rebound height and impact force. Through analysis,we knew, if soil cohesive stress increases, rockfall declining depth will reduce exponentially, and rebound height will linearly increase; if soil elastic modulus increases, rockfall declining depth will linearly reduce, and rebound height reduces exponentially; buffer layer thickness don’t affect obviously declining depth, but is reciprocally related with rockfall rebound height.To sum up, rockfall rebound height is greatly affected by soil cohesive stress、elastic modulus and buffer layer thickness; and rockfall declining depth is greatly affected by soil cohesive stress. Soil cohesive stress and young’s modulus will affect the rockfall impact force. In addition, when soil cohesive stress increases, rockfall impact force will linearly increase; when soil young’s modulus increases, rockfall impact force will reduce exponentially.Because soil cohesive stress and soil thickness have greater effect on rockfall bounce, so when laying buffer layer, the soil cohesive stress should not be too big, the soil thickness should not be too small, reasonable soil thickness still need to be determined according to project site.