节理倾角及连通率对岩体强度、变形影响的单轴压缩试验研究

EXPERIMENTAL STUDY OF EFFECTS OF JOINT INCLINATION ANGLE AND CONNECTIVITY RATE ON STRENGTH AND DEFORMATION PROPERTIES OF ROCK MASSES UNDER UNIAXIAL COMPRESSION

利用含一组张开预置裂隙石膏试件的单轴压缩试验,系统地研究节理组的产状和节理连通率的连续变化对张开断续节理岩体单轴压缩强度和弹性模量及应力–应变曲线的影响。试验研究发现:(1)随着节理连通率的增大,应力–应变曲线的延性增强,由单峰曲线变为多峰曲线;(2)在节理倾角不变时,随着节理连通率的增大,岩体的峰值强度和弹性模量都逐渐降低,且二者变化规律不完全相同,可采用不同幂函数的倒数来表示,其系数与节理倾角有关;(3)当节理连通率不是很大时,岩体的峰值强度和弹性模量随节理倾角的变化规律大致相同,节理倾角为90°时岩体峰值强度和弹性模量最高,节理倾角为30°和60°时岩体的峰值强度和弹性模量最低,出现2个极小值。当节理连通率较大时,节理倾角为90°时岩体的峰值强度和弹性模量最高,节理倾角为45°时岩体的峰值强度最低,节理倾角为0°～60°时岩体的弹性模量都很低。对试件破坏过程的进一步分析表明,上述岩体宏观力学特性随节理倾角和连通率的变化规律,与预制节理的闭合摩擦、岩桥内拉伸和剪切裂纹产生及与预制节理组合形成宏观组合破坏面等细观损伤力学机制密切相关。

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.