Study on the motion law and force chain characteristics of buffer cushion layer of rolling stone impacting shed hole

Mountain bridges and highways frequently implement shed structures to guard against rolling stone disasters. Due to the random and variable nature of the angle at which stones impact sheds, bedding material is often easily displaced, leading to a wider range of potential damages. In this paper, we analyze the effectiveness of varying grades of shed bedding material when struck by rolling stones at different angles. We also examine the mechanism of the microscopic force chains involved in this process through the use of numerical simulations and physical testing.In this paper, numerical simulation and physical tests are carried out to analyze the shovel scraping effect and plowing effect of rolling stone on bedding layer, the energy dissipation effect of bedding material ，and the internal force chain dispersion transfer law, so as to provide a reference for the design of bedding layer of shanty holes. The results show that: (1) with the increase of impact angle, the impact force of the bedding layer under the same level of proportion increases, but the kinetic energy of the rolling stone is smaller, the fine particle group can reduce the kinetic energy of the rolling stone to the minimum at the earliest time, and the medium particle group can buffer the kinetic energy of the rolling stone to the minimum after the end of the impact process so that we can consider mixing the ratio of the fine particle group and the medium particle group to reach the optimal combination of energy dissipation. (2) 60 ° for the most unfavorable impact angle, impact angle on the depth of shovel scraping and plowing height of the influence of the trend line fitting formula for y = ax2 + bx + c, which coefficients a, b, c with the particle size; impact angle is larger, the bedding is shovel scraped the smaller the area, but the roof of the hole will be the greater the peak force. (3) Rolling stone initial impact bedding stage, the lower part of the force chain network rapid formation and stress, but the force chain network then quickly extends to the front end, the stress value becomes smaller; the smaller the particle size of the bedding layer, and the larger the coordination number, that is, the better the degree of contact, the larger the particle size of the bedding layer shoveling effect is not obvious, and the force chain is more solid and not easy to rupture.