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非连续变形分析(DDA)是计算离散可变形块体系统力学响应的数值计算方法,其在连续岩体开裂破坏模拟中的应用也已得到研究。在以往的预离散子块体DDA开裂模拟方法中,通过采用虚拟节理对子块体进行粘结以模拟连续体的变形,进而根据虚拟节理面上的块间接触力判断沿预设节理面的拉伸或剪切破坏。该算法能够较好的模拟岩体的开裂路径和破坏形态,但受预设虚拟节理面方向对块间接触力大小的影响,由此得到的岩石开裂强度与实际之间可能产生较大差异。本研究不再根据块间接触力进行开裂判断,而改进为根据邻近子块体的应力状态进行开裂判断,并仍假定裂纹沿虚拟节理面产生。用新的DDA程序对压缩载荷作用下圆盘试件的拉伸开裂破坏和方形试件的剪切开裂破坏进行了模拟。算例表明,改进后的开裂算法具有高的开裂计算准确性,并大大减小了预设虚拟节理分布对开裂破坏强度及破坏路径模拟结果的影响。
Discontinuous Deformation Analysis (DDA) is a numerical method for calculating the mechanical response of discrete deformable blocks, and its application to the simulation of cracking in continuous rock masses has also been studied. In the conventional DDA cracking simulation of pre-discrete subblocks, subblocks are bonded by using virtual joints to simulate the deformation of the continuum, and then the deformation along the pre-set joint plane is judged based on the inter-block contact force on the virtual facets Tensile or shear damage. The proposed algorithm can simulate the crack path and failure mode of rock mass well. However, depending on the influence of the direction of the pre-set virtual joint plane on the contact force between the rock masses, the rock crack strength obtained may be greatly different from the actual one. In this study, we no longer judge the fracture based on the inter-block contact force, but improve to judge the fracture based on the stress state of the adjacent sub-block, and still assume that the crack is generated along the virtual joint plane. A new DDA program was used to simulate the tensile cracking failure of disk specimens under compressive load and the shear cracking of square specimens. The example shows that the improved crack algorithm has high crack calculation accuracy and greatly reduces the effect of the distribution of the preset virtual joints on the cracking failure strength and the simulation results of the failure path.