Study on the rotation of blocks in two-dimensional block-rock mass

Abstract

Rock mass has complex block-hierarchical structure involving various scale levels, which should be considered both in dynamic and static conditions. Because the interlayer has weak mechanical properties compared with rock blocks, the deformation of rock mass mainly concentrates at the interlayers both in dynamic and static conditions, which provides the possibility of translation and rotation for rock blocks. The basic carriers of pendulum-type wave in rock mass are geoblocks with translational and rotational degrees of freedom involving various hierarchical levels. The major part of the energy of a blast is spent to fragmentation of rocks and is transferred to rock blocks of the stressed geomedium in the form of kinetic energy (including translational kinetic energy and rotational kinetic energy). The in-situ experimental data has shown that the block-rock mass has significant angular deformation under dynamic impact, and the rotation of blocks can deeply affect the wave propagation and dynamic behavior of rock mass. Previous research on 1D dynamic model of block-rock mass cannot reflect the rotation effect of blocks, and the new 2D dynamic model should take into account the rotation of blocks and energy transfer. Consequently, aiming at the investigation of rotation of blocks, the 2D dynamic model of block-rock mass is established based on the accurate consideration of rotation effect. The research based on this model reveals the mechanism of the rotation of blocks, and determines the characteristics of energy transfer and the influence of the rotation of blocks on the inhomogeneous deformation of interlayers. Research shows that the rotation of blocks is not directly related to whether the structure of rock mass is symmetrical, or whether the interlayer is deformed or not, or the form of external loads, but is caused by the non-equilibrium shear between interfaces in the absence of the external torque. The rotation of blocks results in the inhomogeneous deformation of interlayers, and has a significant influence on the shear deformation of interlayers. At some local positions, in addition to the deformation of the interlayer caused by translation, the block-rock mass also produces additional tension and compression deformation caused by the rotation of blocks, which may lead to the phenomenon of rock crushing. This study theoretically solves the problems of wave propagation in block medium under arbitrary loads and torque, and is helpful for the research of seismic wave propagation in block medium with inhomogeneous complex structures.