The shear characteristic and failure mechanism study of infilled rock joints with constant normal load

In order to evaluate the shear deformation characteristics, the direct shear tests for the rock-like specimens with regular sawtooth were carried out in the laboratory. The different asperity angles and different normal stress conditions were considered and the dilatancy characteristics and the corresponding failure modes were analyzed accordingly. The uncommon asperity angle of 25°, 40° and 55° have been selected to compare with the common angles, which can study the differences in detail. Studies show that when the normal stress keeps constant, the peak shear strength increases first and decreases with the increasing asperity angle afterwards. It is because the force causing sawtooth damage under tensile failure is less than the force under shear failure. When the asperity angle keeps constant, the greater the normal stress, the greater the peak shear strength. The larger the normal displacement of dilatancy angle and dilatancy are caused by larger asperity angle. According to the verification, the test results are in good agreement with the analytical results. It should be noted that the analytical results presented locate below the test result curves, which is due to the small values of c and m in the formula. The sliding failure is usually induced when the asperity angle or the normal stress is small. On the contrary, the tensile damage normally occurs while the asperity angle is large enough