单轴压缩下节理间距和倾角对岩体模拟试件强度和变形的影响研究

通过含一组预置张开裂隙石膏试件的单轴压缩试验,系统地研究了当节理连通率固定时,节理组的间距和倾角对试件强度和变形特性的影响。研究发现：①随着节理间距的增大,试件的应力-应变曲线的由单峰型变为多峰型,延性增大。试验中观察到的应力-应变曲线包括4种类型,单峰型、软化段多峰型、多峰平台后软化型和多峰平台后硬化型。②当节理间距不变时,试件的当量化强度、当量化弹性模量和第一峰值应变随节理倾角的变化曲线都呈V型,其最小值发生在节理倾角为45°处;而残余强度与强度之比和第二峰值应变随节理面倾角的变化规律则反之。③当节理倾角不变时,当量化弹模、当量化强度和第一峰值应变都随节理化系数的增大而减小;而残余强度与强度之比和第二峰值应变则反之。④各节理倾角下,试件的当量化弹模和当量化强度随节理化系数的变化规律可以用相同形式的幂函数来表示。⑤上述宏观力学行为与预制节理闭合、次生裂隙发展等细观损伤力学机制密切相关。上述研究表明,节理间距对岩体的强度和变形特性的影响有显著的各向异性。

Experimental study on effect of spacing and inclination angle of joints on strength and deformation properties of rock masses under uniaxial compression

For the gypsum specimens containing a set of preexisting open flaws with fixed joint continuity factor, the influences of inclination angle and spacing of joints on the strength and deformation of the jointed specimens under uniaxial compression are systematically investigated through experiments. It is found that: (1) With the increase of joint spacing, the axial stress-axial strain curve changes from single-peak curve to multi-peak one, indicating that the ductility of the specimens increases. Four types of stress-strain curves are observed, i.e., single-peak, multi-peak during softening stage, softening after multi-peak yield platform and hardening after multi-peak yield platform. (2) For the specimens with constant joint spacing, the curves of the unified Young’s modulus, the unified strength and the first peak strain with the inclination angle of joints are V-shaped, and the minimum occurs at the inclination angle of 45 degrees, while the ratio of the residual strength to the strength and the last peak strain have inverse tendency. (3) For specimens with constant joint inclination angle, with the increase of the jointing index (the reciprocal of the joint spacing), the unified Young’s modulus, the unified strength and the first peak strain decrease, while the ratio of residual strength to strength and the last peak strain increase. (4) For each joint inclination angle, the relation between the unified Young’s modulus and the jointing index and that between the unified strength and the jointing index can be expressed by the power functions. (5) The macroscopic behavior of the jointed specimens is correlated to the closure of pre-existing joints and the cracking process of the specimen matrix. The anisotropic influence of joint spacing on the strength and deformation of jointed rock masses is significant.