断续节理岩体强度与破坏特征的数值模拟研究

基于细观统计损伤数值模型,通过改变包含单组节理岩体的节理倾角、节理台阶角、层距d和岩桥长度l_r,建立不同节理分布的断续节理岩体数值试样,展开系列数值试验,模拟了节理岩体的破坏过程,探讨了节理结构几何参数和应力水平对破坏模式以及岩体力学参数的影响规律。研究结果表明,断续节理岩体破坏模式共分为4种：沿节理面破坏、转动块体破坏、台阶状破坏和混合破坏。沿节理面破坏与台阶状破坏的岩体峰值强度高、破坏应变大,转动破坏的岩体峰值强度低、破坏应变小。随着节理倾角的增大,岩体力学行为表现出脆性破坏—渐进破坏—脆性破坏的循环过程。随着应力水平的增加,岩体破坏区域由中间向端部扩展,并且对于强度的提高有显著作用,但提高水平随围压增加而降低。节理台阶角对于=90°时的破坏形式影响较大,由台阶状破坏转变为转动块体破坏,层距d对阶梯状破坏模式影响较小,对转动破坏模式影响较大,岩桥长度l_r不影响破坏模式,但对面破坏与台阶状破坏模式的峰值强度、破坏应变影响较大。通过对比,模拟结果与物理试验规律一致,但数值模拟结果可以清晰获得节理岩体中应力场分布、裂纹起裂点与扩展方向、破坏图像等,有利于分析其内在破坏规律与机理。

Numerical study on strength and failure modes of rock mass with discontinuous joints

Based on a microscopic statistical damage model, different failure criteria are introduced into a numerical code to simulate tensile breaking and compression shear failure of jointed rock subjected to uniaxial compression and biaxial compression. Influences of geometrical parameters of the joints and lateral stress on fracture patterns and mechanical behaviors are investigated. The results show that the whole failure modes consist of four types: planar failure, stepped failure, rotating-block failure and mixed failure. The planar failure and stepped failure are associated with high strengths and strains, whereas the rotational failure is associated with low strengths and strains. As the joint inclination increases, the peak strength and elastic modulus increase and then decrease. As the lateral stress increases, the failure areas expand from the middle to both ends and appreciably improve the strength, but the increasing level will reduce when the lateral stress continues to increase. The step angle of joints has great influence on the failure modes when =90°, and the failure mode changes from stepped failure to the rotational failure. The layer distance d has slight influence on the stepped failure and great influence on the rotational failure. The rock bridge length l_r does not affect the transition of the failure mode, but it affects the peak strength and failure strain of both the planar failure and stepper failure. The results may provide guidance and reference to jointed rock engineering.