Strength Characteristics of Nonpenetrating Joint Rock Mass under Different Shear Conditions

Yuanming Liu,Shaoyun Pu,Qingzhi Chen

doi:10.1155/2020/3579725

Yuanming Liu, Shaoyun Pu + Show 1 more

Open Access

https://doi.org/10.1155/2020/3579725

Copy DOI

Abstract

The mechanical property of jointed rock mass is an important factor to be considered in the analysis, evaluation, and design of actual rock engineering. The existence of joints threatens the stability and safety of underground engineering projects built in the rock mass. In order to study the change of mechanical properties and strength characteristics of nonpenetrating jointed rock mass under different test conditions, direct shear tests and triaxial tests were carried out. Direct shear tests under different normal stresses were carried out for nonpenetrating jointed rock mass to prepare specimens for triaxial tests. Then, triaxial tests were carried out to study the change of mechanical properties and strength characteristics of the nonpenetrating jointed rock mass. In the direct shear test part, the greater the normal stress is, the stronger the shear strength and the more serious the shear failure would be. The main conclusions are as follows: (1) the strength of rock mass would increase with the increase of confining pressure for those rock specimens with same degrees of shear after the direct shear test; (2) for rock specimens with different degrees of shear after the direct shear test, if the shearing degree of the rock specimen was greater, the strength of the rock specimen would be lower in the triaxial test; (3) for rock specimens with the same damage degree after direct shear test, the greater the normal stress in direct shear test is, the smaller the peak axial pressure would be in the triaxial test; (4) if the specimen was sheared under higher normal stress in direct shear test, the cohesion of it would be lower and the internal friction angle would be larger. For the specimens under the same normal stress, if the shear failure of one specimen was more serious, the cohesion of it would be smaller and the internal friction angle would be larger.

Highlights

After a long-term unbalanced geological process, the rock mass is heterogeneous, anisotropic. e rock mass is a brittle material with dilatancy [1,2,3,4]
In order to study the mechanical properties of nonpenetrating jointed rock mass under complex stress state, shear tests of nonpenetrating jointed rock mass under different working conditions were carried out, and specimens subjected to different shear failure states were obtained. e mechanical properties of rock specimens subjected to different damage degrees are studied by the triaxial test. e following conclusions are drawn from the study: (1) With the greater normal stress of the nonpenetrating jointed rock mass, the shear strength of the rock mass will be stronger and the shear failure of the rock mass will be more severe
(2) For the nonpenetrating jointed rock mass with the same normal stress and the same degree of shear failure in the direct shear test, the strength under triaxial conditions increases with the increasing confining pressure

Summary

Introduction

After a long-term unbalanced geological process, the rock mass is heterogeneous, anisotropic. e rock mass is a brittle material with dilatancy [1,2,3,4]. Rock mass contains irregular and ruleless joints and cracks, and the existing joints and cracks divide rock mass into different blocks [5, 6]. Studying the mechanical properties of the nonpenetrating jointed rock mass is of great significance for both theoretical study and engineering applications [9]. In order to study the mechanical properties of nonpenetrating jointed rock mass, rock-like materials are usually used to replace natural rock materials to prepare test specimens. Rock-like materials can reflect the brittleness and Advances in Civil Engineering dilatancy of rocks, and their mechanical properties are similar to those of conventional rock materials [12,13,14,15]

Methods

Results

Conclusion