수치해석을 통한 진동감쇠식 맞춤형 암반의 감쇠비 산정

초록

The stability of the adjcent structures or slopes under blasting is typically evaluated using an empirical vibrationattenuation curve or dynamic numerical analysis. To perform a dynamic analysis, it is necessary to determine the blastload 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 dampingratio was either ignored or selected without a clear basis in performing a blast analysis. Selection of the dampring ratiofor the rock mass is very difficult because the vibration propagation is influenced by the layout and properties of therock joints. Besides, the vibration induced by blasting is propagated spherically, whereas plane waves are generatedby an earthquake. Since the geometrical spreading causes additional attenuation, the damping ratio should be adjustedin the case of a 2D plane strain analysis. In this study, we proposed equivalent damping ratios for use in continuum2D plane strain analyses. To this end, we performed 2D dynamic analyses for a wide range of rock stiffness andinvestigated the characteristics of blast vibration propagation. Based on numerical simulations, a correlation betweenthe attenuation equation, shear wave velocity, and equivalent damping ratio of rock mass is presented. This novelapproach is the first attempt to select the damping ratio from an attenuation relationship. The proposed chart is easyto be used and can be applied in practice.

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