Abstract

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.

Highlights

  • Most of the literature start with experimental studies to explore the factors that influence the mechanical properties of the structural plane [1,2,3,4,5,6]

  • Xia et al [8] based on the indoor direct shear test, the relationship between the peak displacement of the joint and the roughness of the joint is found to be inversely related to the normal stress, and a new empirical formula for the peak displacement of the structural plane is proposed

  • The conclusions are summarized as follow: 1) The shear characteristic of the specimen is related to the asperity angle

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Summary

Introduction

Most of the literature start with experimental studies to explore the factors that influence the mechanical properties of the structural plane [1,2,3,4,5,6]. It is necessary to accurately study the influence of these parameters on the test piece by simulating the shear characteristics of the filled rock joints. According to sawtooth shear test results carried out by Shen et al [9], the shear strength parameters of joints are proportional to asperity angles. THE SHEAR CHARACTERISTIC AND FAILURE MECHANISM STUDY OF INFILLED ROCK JOINTS WITH CONSTANT NORMAL LOAD. Numerous studies of infilled rock joints with constant normal load (CNL) were carried out to explore shear characteristic [12,13,14,15,16,17]. Researches mainly explore the shear strength of filled rock joints influenced by effects of different factors during the past decades, while this paper focuses on the influence of asperity angles. The failure modes are concluded to explain the causes of the failure of the specimen

Specimen preparation
Penetration tests
Failure modes
Sliding failure
Shear failure
Tensile failure
Analysis of strength characteristics
Analysis of asperity angle on peak shear stress
Analysis of the dilatancy characteristics
Verification between the analytical model and test results
Conclusions
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