Estimation of Attenuation Relationship Compatible with Damping Ratio of Rock Mass from Numerical Simulation

摘要

??? ?? ?? ????? ??? ???? ??? ????? ?? ???? ?? ????? ??? ????. ????? ???? ???? ????? ?? ???? ??? ????. ????? ???? ??? ??? ??? ?????? ??? ???? ?? ??? ????? ?? ? ?? ????? ??? ?? ?? ???? ??? ???? ??. ??? ???? ??? ??? ?? ???? ?? ???? ???? ??. ??, ???? ??? ? ?? ????? ??? ?? ??? ???? ???? ?? 2?? ???? ???? ???? ?? ???? ??? ???? ??? ???? ???? ??. ? ????? ?? ? ?? ??? ??? 2?? ????? ??? ??? ?? ??? ??? ?????? ?????. ?? ??? ??? ??? ??? ?? 2?? ????? ???? ??? ???? ?? ???? ??? ?????? ????? ???? ?????-?????-??????? ????? ?????. ??? ????? ??? ?????? ???? ???? ??? ??? ??? ??? ??? ??? ??? ???? ?? ??? ? ?? ??? ????.The stability of the adjcent structures or slopes under blasting is typically evaluated using an empirical vibration attenuation curve or dynamic numerical analysis. To perform a dynamic analysis, it is necessary to determine the blast load and the damping ratio of rock mass. Various empirical methods have been proposed for the blast load. However, a study on representative values of damping ratio of a rock mass has not yet been performed. Therefore, the damping ratio was either ignored or selected without a clear basis in performing a blast analysis. Selection of the dampring ratio for the rock mass is very difficult because the vibration propagation is influenced by the layout and properties of the rock joints. Besides, the vibration induced by blasting is propagated spherically, whereas plane waves are generated by an earthquake. Since the geometrical spreading causes additional attenuation, the damping ratio should be adjusted in the case of a 2D plane strain analysis. In this study, we proposed equivalent damping ratios for use in continuum 2D plane strain analyses. To this end, we performed 2D dynamic analyses for a wide range of rock stiffness and investigated the characteristics of blast vibration propagation. Based on numerical simulations, a correlation between the attenuation equation, shear wave velocity, and equivalent damping ratio of rock mass is presented. This novel approach is the first attempt to select the damping ratio from an attenuation relationship. The proposed chart is easy to be used and can be applied in practice.???