基于改进刚体弹簧方法的断续双裂隙砂岩强度及裂纹扩展特征研究

Numerical Study on Strength and Crack Coalescence Behavior of Sandstone Containing Two Pre-existing Non-coplanar Fissures Based on Improved Rigid Body Spring Method

为研究含非共面双裂隙砂岩的强度及裂纹扩展特征,以室内试验结果标定砂岩细观参数,建立含不同岩桥倾角的双裂隙数值计算模型,采用改进刚体弹簧方法对其单轴压缩过程进行模拟。基于模拟结果,研究了岩桥倾角对起裂应力、峰值强度、破坏模式和裂纹扩展特征的影响。结果表明:岩桥倾角<60°,起裂应力和峰值强度均随岩桥倾角增大而减小,岩桥倾角>60°,均随岩桥倾角增大而增大;根据岩桥倾角不同,裂隙试样破坏模式呈现单一翼裂纹轴向贯通破坏、翼裂纹与翼裂纹搭接贯通破坏和翼裂纹与预制裂纹搭接贯通破坏3种类型;岩桥倾角对岩桥破坏程度有影响,60°岩桥贯通最易,0°和120°岩桥贯通最难。研究结果可为岩土工程的稳定分析提供参考。

In order to study the strength and crack coalescence behavior of sandstone containing two pre-exisiting non-coplanar fissures,a modified Rigid Body Spring Method is proposed to simulate the process of uniaxial compression tests,and a set of micro-parameters calibrated by uniaxial compression laboratory test results was used to set up a model of fissured rock samples containing two pre-exisiting non-coplanar fissures.On the basis of the simulated results,the influence of rock bridge inclination on crack initiation stress,peak strength,failure mode and crack coalescence behavior was investigated.Results show that crack initiation stress and peak strength both decreased in the presence of a rock bridge inclination smaller than 60°,and vice versa.According to the differences of the rock bridge inclination,the failure mode of specimens could be divided into three types：the penetration failure of single wing crack,the penetration failure of the coalescence of wing crack and the penetration failure of the coalescence between wing crack and prefabricated fissures.Rock bridge inclination has some impact on the failure degree of the rock bridge,and it is easy to coalesce for 60° rock bridge but hard for 0° and 120° rock bridge.