The characteristics of rock instability precursors and the principal stress direction are very crucial for the prevention of geological disasters.This study investigated the qualitative relationship between rock insta...The characteristics of rock instability precursors and the principal stress direction are very crucial for the prevention of geological disasters.This study investigated the qualitative relationship between rock instability precursors and principal stress direction through wave velocity in rock acoustic emission(AE)experiments.Results show that the wave velocity variation exhibits obvious anisotropic characteristics in 0%–20%and 60%–90%of peak strength due to the differences of stress-induced microcrack types.The amplitude of wave velocity variation is related to the azimuth and position of wave propagation path,which indicates that the principal stress direction can be identified by the anisotropic characteristics of wave velocity variations.Furthermore,the experiments also demonstrate that the AE event rate and wave velocity show quiet and stable variations in the elastic stage of rock samples,while they present a trend of active and unstable variations in the plastic stage.It implies that both the AE event rate and wave velocity are effective monitoring parameters for rock instability.The anisotropic characteristics of the wave velocity variation and AE event rate are beneficial complements for identifying the rock instability precursors and determining the principal stress direction,which provides a new analysis method for stability monitoring in practical rock engineering.展开更多
The rocks in the crust are pervaded by stress-aligned fluid-saturated microcracks, and the complex fault tectonics and stress control the configuration of the microcracks, however shear-wave splitting could indicate t...The rocks in the crust are pervaded by stress-aligned fluid-saturated microcracks, and the complex fault tectonics and stress control the configuration of the microcracks, however shear-wave splitting could indicate this kind of characteristics. In this paper, Capital Area Seismograph Network (CASN), the widest scope and highest density of regional seismograph network presently in China, is adopted to deduce the principal compressive stress field distribution pattern from polarizations of fast shear- waves, based on shear-wave splitting analysis. The principal compressive stress in capital area of China is at NE85.7°± 41.0° in this study. Compared with the results of principal compressive stress field in North China obtained from other methods, the results in this study are reliable in the principal com- pressive stress field distribution in capital area. The results show that it is an effective way, although it is the first time to directly obtain crustal stress field from seismic anisotropy. It is effectively applied to the zones with dense seismograph stations.展开更多
基金the financial support from the Fundamental Research Funds for the Central Universities(No.2282020cxqd055)the National Science Foundation for Excellent Young Scholars of China(No.51822407)+1 种基金the Natural Science Foundation of China(Nos.51774327 and 51504288)the Fundamental Research Funds for the Central Universities of Central South University(No.2021zzts0862)。
文摘The characteristics of rock instability precursors and the principal stress direction are very crucial for the prevention of geological disasters.This study investigated the qualitative relationship between rock instability precursors and principal stress direction through wave velocity in rock acoustic emission(AE)experiments.Results show that the wave velocity variation exhibits obvious anisotropic characteristics in 0%–20%and 60%–90%of peak strength due to the differences of stress-induced microcrack types.The amplitude of wave velocity variation is related to the azimuth and position of wave propagation path,which indicates that the principal stress direction can be identified by the anisotropic characteristics of wave velocity variations.Furthermore,the experiments also demonstrate that the AE event rate and wave velocity show quiet and stable variations in the elastic stage of rock samples,while they present a trend of active and unstable variations in the plastic stage.It implies that both the AE event rate and wave velocity are effective monitoring parameters for rock instability.The anisotropic characteristics of the wave velocity variation and AE event rate are beneficial complements for identifying the rock instability precursors and determining the principal stress direction,which provides a new analysis method for stability monitoring in practical rock engineering.
基金the National Natural Science Foundation of China (Grant No. 40674021)IES-CEA Project (Grant No. 2007-13)
文摘The rocks in the crust are pervaded by stress-aligned fluid-saturated microcracks, and the complex fault tectonics and stress control the configuration of the microcracks, however shear-wave splitting could indicate this kind of characteristics. In this paper, Capital Area Seismograph Network (CASN), the widest scope and highest density of regional seismograph network presently in China, is adopted to deduce the principal compressive stress field distribution pattern from polarizations of fast shear- waves, based on shear-wave splitting analysis. The principal compressive stress in capital area of China is at NE85.7°± 41.0° in this study. Compared with the results of principal compressive stress field in North China obtained from other methods, the results in this study are reliable in the principal com- pressive stress field distribution in capital area. The results show that it is an effective way, although it is the first time to directly obtain crustal stress field from seismic anisotropy. It is effectively applied to the zones with dense seismograph stations.
