Authors: Jianhua Yang Wenbo Lu Ming Chen Peng Yan Chuangbing Zhou
Publish Date: 2012/09/28
Volume: 46, Issue: 4, Pages: 859-875
Abstract
During deep rock mass excavation with the method of drill and blast accompanying the secession of rock fragments and the formation of a new free surface in situ stress on this boundary is suddenly released within several milliseconds which is termed the transient release of in situ stress In this process enormous strain energy around the excavation face is instantly released in the form of kinetic energy and it inevitably induces microseismic events in surrounding rock masses Thus blasting excavationinduced microseismic vibrations in highstress rock masses are attributed to the combined action of explosion and the transient release of in situ stress The intensity of stress releaseinduced microseisms which depends mainly on the magnitude of the in situ stress and the dimension of the excavation face is comparable to that of explosioninduced vibrations With the methods of time–energy density analysis amplitude spectrum analysis and finite impulse response FIR digital filter microseismic vibrations induced by the transient release of in situ stress were identified and separated from recorded microseismic signals during a blast of deep rock masses in the Pubugou Hydropower Station The results show that the lowfrequency component in the microseismic records results mainly from the transient release of in situ stress while the highfrequency component originates primarily from explosion In addition a numerical simulation was conducted to demonstrate the occurrence of microseismic events by the transient release of in situ stress and the results seem to have confirmed fairly well the separated vibrations from microseismic records
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