不同应力途径三轴压缩下岩石的声发射
ACOUSTIC EMISSION OF ROCKS UNDER TRIAXIAL COMPRESSION ALONG VARIOUS STRESS PATHS
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摘要: 在不同加载方式的三轴实验中,观测了济南辉长岩和北京昌平花岗岩的声发射(围压达1.3千巴).当最大主应力增加使岩样破坏时(A型),平均声发射率逐渐增加,离破裂强度约几百巴时声发射急剧增多.而当岩石处于一定的高应力状态,通过减小围压使岩样破坏时(B型),声发射的急剧增加仅出现在离破裂差应力20-30巴的情况下,而且这种破裂过程声发射总数只有 A 型的1/3左右.在 B 型加载情况下,从应力场的球张量部分(流体静压力)来看,是一个卸载过程,而从偏张量部分来看,是一个加载过程.这种卸载过程的存在很可能是造成声发射不同特征的主要原因.Abstract: Acoustic emission of Jinan gabbro and Shangpin granite samples has been observed under triaxial compression along various stress paths (confining pressure up to 1.3 kb). When the maximum principal stress was increased until the rock sample failed (case A), the average acoustic emission rate gradual increased, an abrupt increase of acoustic emission occurred at about several hundred bars prior to rupture. When starting from a high stress state and the confining pressure was decreased (caseB), an abrupt increase of acoustic emission occurred much later, only about 20-30 bars before rupture. The total number of acoustic emission in the fracture process was much less only one-third of that in case A. There were two processes in case B: loading process for differential tensor component of the stress field; unloading process for spherical symmetric tensor componen (hydrostatic). It is possible that the different characteristics of acoustic emission is due to the existence of the unloading process.
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[8] R.W B. Stepliens, A. A.Polloek, Waveform and frequency spectra of acoustic emission,J. of Acoustic Society of America,50,3,904——910,1970[1] K Mogi, Earthquakes as fractxxre in the earth, in "Advances in Rock Mechanics"Proc. 3rd.Conf. Int. Soc. Rock Mechanics, IA, 559——568. 1974.
[2] C. H. Seholz, Experimental study of the fracturing process in brittle rocks, J. Geophys. Res., 73,1447——1454,1968
[3] C. F. Bacon, Acoustic emission along the San Andreas fault in southern central California, Ma——terials evaluation,34.5. 1976.
[4] J. D. Byerlee, A review of rock mechanics studies in the United States pertinent to earthquake prediction, PAGEOPH, 116(4/5),586——602, 1978
[5] K, Mogi, Study of elastic shocks caused by the fracture of heterogeneous materials, and its rela——tion to the earthquake phenomena, Bull. Eartla. Res. Inst., 40, 1, 105——173, 1962
[6] H. J. Alheid and F. Rummel. Acoustic emission during frietiona.l sliding along shear planes in rock in "Proc. First conf. on Acoustic Emission/Microscismic Activity in Geological Sttuctttre and Materials",149——154. 1977.
[7] R Chen, N .G. Geng, and X. X. Yiao, Strength and volume changes of rocks under triaxial com——pression with various stress paths, Submitted to Scientia ,Sinica. 11. 1093——1100. 1979
[8] R.W B. Stepliens, A. A.Polloek, Waveform and frequency spectra of acoustic emission,J. of Acoustic Society of America,50,3,904——910,1970
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