软硬互层岩体力学及变形特性的离散元模拟

Discrete Element Simulation on the Mechanical and Deformation Characteristics of Soft and Hard Interbedded Rock Mass

采用离散元软件PFC2D模拟软硬互层岩体渐进破裂过程,研究倾角、软硬层厚比和围压对其力学特性及变形特性的影响。研究结果表明:(1)软硬互层岩体抗压强度、黏聚力、内摩擦角和弹性模量随岩层倾角的增加先减小后增大,随围压的增加逐渐增大,随软层厚度的增加逐渐减小;(2)软硬互层岩体强度与其单结构面理论强度分布规律大致相同,但实际强度没有保持不变的倾角范围,且在最不利破坏倾角α=π/4+φ_(j)/2附近的变化幅度也没有单结构面理论强度明显;(3)硬层中生成贯穿层理面裂隙所需应变随软层厚度增大,增大岩体裂隙数量发展速度随岩体倾角的增加先增加后减小,在45°或60°时达到峰值,围压增大,岩体裂隙发展越充分;(4)软硬互层岩体在岩层倾角0°时为贯穿层理面的张剪破坏,在30°~60°时为沿层理面的剪切滑移破坏,90°时为沿层理面和局部贯穿层理面的复合张剪破坏;(5)围压的增大会诱发岩体发生剪切破坏,而软层厚度的增加可增强岩体破坏时的完整性。

The discrete element software PFC2D is used to simulate the progressive failure process of soft and hard interbedded rock masses,and the influence of layer dip,soft and hard layer thickness ratio and confining pressure on its mechanical properties and deformation characteristics are studied.The results show that:(1)The compressive strength,cohesion,internal friction angle and elastic modulus of the soft and hard interbedded rock mass first decrease and then increase with the increase of the rock inclination,they gradually increase with the increase of confining pressure,and they decrease as the layer thickness gradually increase.(2)The strength of the soft and hard interbedded rock mass is roughly the same as the theoretical strength distribution of its single structural plane,but the actual strength does not have a constant dip range,and changes near the most unfavorable failure dipα=π/4+φ_(j)/2 The amplitude is not as obvious as the theoretical strength of a single structural plane.(3)The strain required to generate the through-bedding surface cracks in the hard layer increases as the thickness of the soft layer increases;and the development speed of the rock mass cracks first increases and then decreases as the rock inclination angle increases,reaching a peak at 45°or 60°;As the confining pressure increases,the cracks in the rock mass develop more fully.(4)The soft and hard interbedded rock mass is tensile-shear failure through the bedding plane when the rock inclination is 0°,shear-slip failure along the bedding plane at 30 to 60°,and along the bedding plane at 90°The composite tensile-shear failure of the surface and the partially penetrated bedding surface;(5)the increase of confining pressure can induce the shear failure of the rock mass,and the increase of the thickness of the soft layer can enhance the integrity of the rock mass when it fails.