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| EXPERIMENTAL STUDY OF EFFECTS OF JOINT INCLINATION ANGLE AND CONNECTIVITY RATE ON STRENGTH AND DEFORMATION PROPERTIES OF ROCK MASSES UNDER UNIAXIAL COMPRESSION |
(1. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and Technology，Beijing 100083，China；2. School of Mechanics and Civil Engineering，China University of Mining and Technology，
Beijing 100083，China) |
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Abstract Influences of the two important geometrical parameters of joint inclination angle and joint connectivity rate of a joint set，on uniaxial compression strength，elastic modulus and stress-strain curves of rock mass with non-persistent open joints，are investigated systematically by conducting uniaxial compression tests on gypsum specimens with a set of preexisting open flaws. It is found that：(1) With the increasing of joint connectivity rate，the ductility of axial stress-axial strain curves increases，and they change from single-peak curves to multi-peak curves. (2) At the same joint inclination angle，the peak strength and elastic modulus of specimens decrease with the increasing of joint connectivity rate，which can be estimated by two kinds of power functions respectively，where their parameters are varied with joint inclination angle. (3) When joint connectivity rate is not very large，the peak strength and elastic modulus of specimens are varied with the joint inclination angles in the similar way，i.e. they are the highest at the joint inclination angle of 90° while they are the lowest at the joint inclination angles of 30° and 60°. When joint connectivity is very large，the peak strength and elastic modulus of specimens are the highest at the joint inclination angle of 90°，while peak strength is the lowest at the joint inclination angle of 45° and the elastic modulus is relatively lower below 60°，respectively. Through further analyses for failure process of the specimens，it is revealed that the jointed rock mass macroscopic mechanical properties affected by joint inclination angle and joint connectivity rate are governed by microscopic damage mechanism，such as closure and friction of the preexisting joints，stress concentrate in the rock bridge and induce crack initiation，propagation and their coalescence with the preexisting flaws to form the final failure planes or shear bands.
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Received: 23 December 2010
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2011, Vol. 30 
