Investigation of Stress Wave Propagation Through Rock Masses with Double-scale Discontinuities by a Split Three Characteristic Lines Method
Meng WANG+, Qihao YANG, Lifeng FAN#
Beijing University of Technology, China

The study of stress wave propagation in natural rock masses is significant for the dynamic stability of rocks. Discontinuities ranging from micro-defects to macro-joints are widely existing in natural rock masses, which have a significant effect on stress wave propagation.Currently, the traditional methods have been successfully applied to stress wave propagation through single-scale discontinuous rock masses. The stress wave propagation through the macro-jointed rock masses can be solved by the two characteristic lines method combined with the displacement discontinuity model (DDM). In addition, practical rock masses are generally micro defected, which can be equivalently described by a viscoelastic medium. The traditional three characteristic lines method was developed to solve the stress wave propagation through the micro-defected rock mass. Because the effects of micro-defects and macro-joints in rock mass on stress wave attenuation of velocity and amplitude are different in the mechanism. Therefore, it is still difficult to analyze the stress wave propagation through double-scale discontinuous rock masses containing micro-defects and macro-joints. To solve the stress wave propagation through rock masses with double-scale discontinuity, a split three characteristic lines method combined with DDM was proposed in the present study. The three characteristic lines are split at the location of a single macro-joint. So that the split three characteristic lines are divided into three basic elements: triangle, diamond, and separated diamond elements. Similar to the traditional three characteristic lines method, the triangle, and diamond elements are used to solve stress wave propagation at left boundary points and ordinary interior points of the rock mass. To further study the stress wave propagation at the macro-joint, the separated diamond element is proposed. The DDM is introduced into the separated diamond element to solve wave propagation at pre-interior points and post-interior points of the macro-joint. The results show that the present method can be used to investigate the stress wave propagation through double-scale discontinuities efficiently.