Cracking process of rock mass models under uniaxial compression  

作　　者：陈新 廖志红 彭曦 

机构地区：[1]State Key Laboratory for GeoMechanics and Deep Underground Engineering [2]School of Mechanics and Civil Engineering,China University of Mining and Technology(Beijing)

出　　处：《Journal of Central South University》2013年第6期1661-1678,共18页中南大学学报（英文版）

基　　金：Project(11102224)supported by the National Natural Science Foundation of China;Project(2009QL05)supported by the Fundamental Research Funds for the Central Universities of China

摘　　要：Anisotropic strength and deformability of the rock mass with non-persistent joints are governed by cracking process of the rock bridges. The dependence of cracking process of jointed rock masses on the two important geometrical parameters, joint orientation and joint persistence, was studied systematically by carrying out a series of uniaxial compression tests on gypsum specimens with regularly arranged multiple parallel pre-existing joints. According to crack position, mechanism and temporal sequence, seven types of crack initiations and sixteen types of crack coalescences, were identified. It was observed that both tensile cracks and shear cracks can emanate from the pre-existing joints as well as the matrix. Vertical joints were included and coplanar tensile cracks initiation and coalescence were observed accordingly. For specimen with joint inclination angle ,8=75~, it was found that collinear joints can be linked not only by coplanar shear cracks but also by mixed tensile-shear cracks, and that a pair of them can form a small rotation block. Seven failure modes, including axial cleavage, crushing, crushing and rotation of new blocks, stepped failure, stepped failure and rotation of new blocks, shear failure along a single plane and shear failure along multiple planes, were observed. These modes shift gradually in accordance with the combined variation of joint orientation and joint persistence. It is concluded that cracking process and failure modes are more strongly affected by joint orientation than by joint persistence, especially when joint inclination angle is larger than 45~. Finally, variations of macroscopic mechanical behaviors with the two geometrical parameters, such as patterns of the complete axial stress-axial strain curves, peak strength and elastic modulus, are summarized and their mechanisms are successfully explained according to their different cracking process.Anisotropic strength and deformability of the rock mass with non-persistent joints are governed by cracking process of the rock bridges.The dependence of cracking process of jointed rock masses on the two important geometrical parameters,joint orientation and joint persistence,was studied systematically by carrying out a series of uniaxial compression tests on gypsum specimens with regularly arranged multiple parallel pre-existing joints.According to crack position,mechanism and temporal sequence,seven types of crack initiations and sixteen types of crack coalescences,were identified.It was observed that both tensile cracks and shear cracks can emanate from the pre-existing joints as well as the matrix.Vertical joints were included and coplanar tensile cracks initiation and coalescence were observed accordingly.For specimen with joint inclination angle β=75°,it was found that collinear joints can be linked not only by coplanar shear cracks but also by mixed tensile-shear cracks,and that a pair of them can form a small rotation block.Seven failure modes,including axial cleavage,crushing,crushing and rotation of new blocks,stepped failure,stepped failure and rotation of new blocks,shear failure along a single plane and shear failure along multiple planes,were observed.These modes shift gradually in accordance with the combined variation of joint orientation and joint persistence.It is concluded that cracking process and failure modes are more strongly affected by joint orientation than by joint persistence,especially when joint inclination angle is larger than 45°.Finally,variations of macroscopic mechanical behaviors with the two geometrical parameters,such as patterns of the complete axial stress-axial strain curves,peak strength and elastic modulus,are summarized and their mechanisms are successfully explained according to their different cracking process.

关 键 词：rock mass joint orientation joint persistence uniaxial compression fracture process 

分 类 号：TU45[建筑科学—岩土工程]