Effect of concave terrain on explosion-induced ground motion

Abstract

During blasting application, ground motions are inevitably induced and have an adverse impact on the safety of surrounding structures. An artificial or natural concave terrain may cause the amplification or reduction of ground motion due to the complex interactions between the explosion-induced seismic waves and the concave terrain. It is essential to analyze the complex interactions, and to estimate the effectiveness of the ground motion amplification or reduction by the concave terrain. Field tests were firstly conducted to acquire the ground particle velocities . It is primarily found from the monitored data that the ground motions before the concave terrain are amplified, while those on the bottom and behind the concave terrain are reduced. In order to explore the mechanism, the boundary integral equation method was then adopted to obtain the motions of the whole field. By comparisons with the results from the finite element method (FEM) and the field tests, the present method was proved to be effective. The complex interactions were described in detail between those explosion-induced seismic waves and a rectangular concave terrain. The wave reflection, as well as the mode conversions among compressional, shear and Rayleigh waves , causes the amplification or reduction of ground motion. The depth of concave terrain has a negligible effect on the ground motion amplification before the concave terrain. On the contrary, ground motion intensity becomes lower on the bottom and behind deeper concave terrain.