Abstract
An experimental study of a rock-like material containing a preexisting fissure subjected to loading and unloading triaxial compression is carried out, and the results show that the mechanical characteristics of the rock-like specimen depend heavily on the loading paths and the inclination of the fissure. The triaxial loading experiment results show that the failure strength linearly increases, while the residual strength linearly decreases with increasing inclination. Furthermore, specimens subjected to triaxial compression show an “X”-type shear failure mode. The triaxial unloading compression experimental results show that specimens with different inclination angles have various failure modes. Specimens with gentle inclinations show a tensile-shear mix failure mode, specimens with middle inclinations show a shear-sliding failure mode, and specimens with steep inclinations show a tensile failure mode. These findings can be used to forecast excavation-induced instabilities in deep underground engineering rock structures.
Highlights
Excavation-induced instability and failure of deep underground rock structures are closely associated with the mechanical behavior of rock masses exposed to loading and unloading of the confining pressure [1]
Analysis of the Stress-Strain Curves of the Triaxial Compression Tests. e stress-strain curves of the specimens with open-through fissures show multipeak characteristics under triaxial compression. ese can be divided into seven stages: fissure compaction, elastic deformation, crack growth and penetration, strain softening, void recompaction, progressive failure, and a residual stage. e preexisting fissure is mainly compacted during the initial compaction stage; the brittle failure stage is followed by ideal strain softening and later a void recompaction process that is mainly caused by inner void and pore compaction
We carried out conventional triaxial compression and triaxial compression with prepeak circumferential unloading tests on the rock-like specimens with preexisting fissures. e stress-strain relationship, strength, deformation, and failure modes of the specimens were studied. e following main conclusions are drawn: (1) e stress-strain curves in the postpeak stage of the rock-like specimens with preexisting fissures are characterized by a zigzag behavior under the type I test. e trends of the zigzag curves are closely related to the fissure inclinations. e stress drops in the postpeak stage under the type II test
Summary
Excavation-induced instability and failure of deep underground rock structures are closely associated with the mechanical behavior of rock masses exposed to loading and unloading of the confining pressure [1]. It is of great importance to illustrate the effect of loading and unloading triaxial compressions on the mechanical behavior of rock masses and to disclose the fundamentals of excavation-induced instability. Erefore, it is of great practical significance to take loading and unloading conditions into consideration and to study the deformation and mechanical behaviors of fractured rock masses. It is of great importance to study the mechanical characteristics and failure modes of fractured specimens with preexisting fissures under loading and unloading triaxial compression. Is paper experimentally studies the mechanical behavior of the rock-like specimens containing preexisting fissures under loading and unloading triaxial compression. E deformation and failure modes of the specimens under different loading paths and the influence of the fissure inclination are investigated
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