Abstract
Direct shear tests were carried out on nonthrough jointed rock masses (NTJRM) with three types of joints under five normal stresses. The strength characteristics of shear strength, initial crack strength, and residual strength and the deformation characteristics of tangential displacement and dilatancy displacement as well as the transformation of failure mode and the variation of shear parameters of rock mass with different joint morphology are studied. Under the same normal stress, with the increase of joint undulation, the shear strength of NTJRM increases, and the corresponding tangential displacement of NTJRM increases. Two typical failure modes are observed: TTTS mode and TSSS mode. TTTS model indicates that the initial failure, extension failure, and final failure of rock mass are caused by tensile action, while the failure mode of through plane is formed by shear action. The initial failure of TSSS mode rock mass is caused by tensile action, while the expansion and final failure are caused by shear action, and the failure mode of through plane is formed under shear action. When the joint undulation is small and the normal stress is small, NTJRM will fail in TTTS mode; when the joint undulation is large and the normal stress is large, NTJRM will fail in TSSS mode. The results show that the shear parameters of NTJRM are related to the joint morphology, the bond force increases with the increase of joint undulation, and the internal friction angle increases with the increase of joint undulation. The research results of direct shear test of nonthrough jointed rock mass can provide reference for related research.
Highlights
Jointed rock mass is a familiar complex engineering-geological body in nature [1], in which the joint plays an essential role in reducing the rock mass strength [2,3,4]. e close association between internal joints coalescence and failure in rock engineering has been proven by various studies [5,6,7,8]
The failure mechanism of nonthrough jointed rock mass (NTJRM) is different from NTJRM. erefore, it is of great significance to investigate the shear strength and failure characteristics of NTJRM
Under the same normal stress, the shear strength, initial crack strength, and residual strength of rock mass with nonthrough joints increase with the increase of undulation angle
Summary
Jointed rock mass is a familiar complex engineering-geological body in nature [1], in which the joint plays an essential role in reducing the rock mass strength [2,3,4]. e close association between internal joints coalescence and failure in rock engineering has been proven by various studies [5,6,7,8]. Jointed rock mass is a familiar complex engineering-geological body in nature [1], in which the joint plays an essential role in reducing the rock mass strength [2,3,4]. The failure mechanism of NTJRM is different from NTJRM. Erefore, it is of great significance to investigate the shear strength and failure characteristics of NTJRM. A number of researches have been carried out to understand the influence of different joint geometry parameters on the mechanical behavior of NTJRM. Bobet and Einstein [9] investigated the failure modes of specimens with two different types of joints under uniaxial loading. Wong and Chau [10] performed uniaxial loading tests on rock-like specimens containing double joints and summarized the relationship between failure modes and joint angles and rock bridges
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