Experimental study on the maximum impact force by rock fall

Abstract

The maximum impact force caused by a rockfall is a very important factor for the design of protection measures for houses, roads, and bridges. To establish an impact force model, the kinetic energy of the rock block, the impact angle between the movement direction of the block and the surface of the object hit by the block, and the modulus of elasticity of rock and object were analyzed with the Buckingham theorem and simplified to two dimensionless parameters. Physical tests were conducted with different kinetic energies, moduli of elasticity of the rock, and the object. Balls of iron, granite, marble, sandstone, and wood were used to simulate rock blocks in the tests. The objects hit by the balls are composed of steel, concrete, and wood. The relationships between the maximum impact force and the kinetic energy, and modulus of elasticity determined by dimensional analysis were confirmed by these experiments. Experiments were carried out with different impact angles to determine the influence of the impact angle on the impact force. A maximum impact force model is obtained from these relationships and by experiments with impact forces ranging from 225 to 15,583 N. A comparison with results reported from other studies shows that the maximum impact force model gives reasonable results over a very large range of impact forces from 21.4 to 8.16 MN. We assume that the model can be used to calculate the impact force at the full field scale.