Abstract
In nature, rock mass is subjected to compression-shear effect, so it is very important to study the failure mode and mechanical properties of fractured rock mass under compression-shear effect. In order to study the influence of joint inclination on strength characteristics and failure modes of rock mass under different compression-shear angles, a series of compression-shear tests were carried out. The specimens are made of a certain proportion of fine sand, cement and water. The joints are prefabricated by inserting mica sheets and the inclination angle of joints is 0°, 15°, 30°, 45°, 60°, 75°, 90°. Digital speckle correlation method is used to analyze the strain field of the specimen during the whole loading process. The specimens are speckled on the opposite side before the experiment. In the experiment, the front and back sides of the specimen are monitored by the camera, and the images are analyzed after the experiment. The result shows that: 1) The peak shear strength of specimens mainly increases with the increase of joint inclination angle; 2) The weakening degree of shear strength caused by joint inclination angle of specimens tends to increase as the compression-stress ratio increases; and 3) The failure modes can be classified into four types: coplanar shear failure mode, inclined shear failure mode, quasi-complete shear failure mode and step shear failure mode. The digital speckle strain images better prove the failure modes obtained from the experiment.
Highlights
In practical engineering, the failure of rock mass structure is usually accompanied by the crack initiation, propagation and coalescence between joints and fissures, and the overall movement resulting from this will cause the failure of rock mass structure in engineering
1) The shear strength of specimens is sensitive to the change of joint inclination angle
It can be seen that the peak shear strength of specimens increases with the increase of joint inclination angle, except that the shear strength of specimens with joint inclination angle of 60 degrees is relatively low at compression-shear angle of 30 degrees
Summary
The failure of rock mass structure is usually accompanied by the crack initiation, propagation and coalescence between joints and fissures, and the overall movement resulting from this will cause the failure of rock mass structure in engineering. H. Cao et al [8] studied the mechanical characteristics and failure behaviors of the rock mass by carrying out the uniaxial compression test on rock-like specimens with holes. STRENGTH CHARACTERISTICS AND FAILURE BEHAVIOR OF UBIQUITOUS-JOINT ROCK-LIKE SPECIMENS UNDER COMPRESSIVE-SHEAR STRESS: EXPERIMENTAL STUDY AND DIGITAL SPECKLE CORRELATION METHOD. Wang et al [15] use numerical method to simulate the jointed specimen under compression-shear loading and found the crack propagation and failure modes have a great agreement with the results obtained in the experiment. There are only a few studies on strength characteristics and failure modes of rock mass under compression-shear conditions, and they mainly focus on specimens with single crack or multiple cracks. Ubiquitous joint rock-like specimens under compression-shear loading are studied in this experiment to find out the mechanical properties and the failure modes
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