Abstract
The instability of rock engineering is normally dominated by the shear failure of rock mass. The dip angle of discontinuous planes widely existing in rock mass is a key parameter affecting the shear strength and failure mode of jointed rock. This paper aims to investigate the influence of discontinuous joints on the shear failure of rock. Direct shear tests are carried out on rock-like specimens with discontinuous joints in different dip angles. During the shear tests, the strain field is monitored in real-time by digital image correction (DIC) technology. Experimental results show that the shear strength, shear strain evolution, and failure mode for the jointed specimens are affected by the dip angles of the discontinuous joints. The maximum shear strain of specimens with joint angles of 45° and 75° increases gradually with the increase of shear loading. The maximum shear strain for the specimens with joint angles of 0°, 15°, 30°, 60°, and 90° increases sharply after the shear load reaches 80% of the peak load. When the joint inclination angle is less than 45°, the crack begins to expand from the joint tip and is interconnected to form a penetrating fracture. When the joint dip angle is greater than 45°, the cracks initiate at the joint tip and then propagate at different paths resulting in multistage shearing and crushing failure.
Highlights
Experimental Method or ProceduresDigital image correlation (DIC) is a method to spray a random pattern called speckles pattern on the surface to be measured and to analyze the deformation degree of samples by comparing and analyzing the images before and after deformation
Testing Methods and digital image correction (DIC) Brief Principles. e rock shear test machine (TFD-20H/50J) of Changchun Keyi Testing Instrument Co., LTD is used in direct shear tests. e normal maximum load is 20 kN, and the tangential maximum load is 50 kN
Based on digital image correlation technology, the shear strain field of the model shear process was monitored in real time. e research results provided an important experimental reference for revealing the mechanism of shear crack initiation, expansion, and instability of preset rock. e conclusions are as follows: (1) e joint dip angle has a significant influence on the evolution process of shear strain and the change law of maximum shear strain of the joint specimen
Summary
Digital image correlation (DIC) is a method to spray a random pattern called speckles pattern on the surface to be measured and to analyze the deformation degree of samples by comparing and analyzing the images before and after deformation. It can detect the amount of deformation and the direction of deformation. E digital cameras are used to collect speckle images on the surface of the specimens during the test process at a high frequency. E displacement and deformation data of the specimens in the full-field and fulltime domain are collected. After the specimen is made and formed, a thin layer of white paint is sprayed on the surface of the
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