基于应变局部化的双裂纹岩样贯通模式及强度试验研究

含裂隙岩体在外力作用下,内部裂纹会发生扩展,这会显著影响强度以及损伤特性。基于前期验证可靠的DIC系统,对含双裂纹的类岩石材料进行单轴压缩试验,捕获全过程的应变场演化云图以及岩桥区域应变局部化过程,研究发现:岩样呈现出显著的变形局部化渐进破坏特性;试验初期形成的应变局部化带基本确定了加载全程全局应变场的变化范围与变化趋势;基于试验研究,双裂纹岩样的贯通破坏模式可归总为4类:岩桥不贯通模式、裂纹内尖端贯通模式、裂纹内外尖端贯通模式以及裂纹外尖端贯通模式;岩桥角度及其空间排布在细观上影响了应变场局部化带的演化过程,宏观上决定了裂纹的扩展路径及岩样的破坏模式;岩桥贯通时应变局部化带的融合造成了应力–应变曲线的"峰前波动",使得岩样强度降低,并且融合越慢岩样强度越高。

EXPERIMENTAL STUDY OF COALESCENCE MODE OF CRACKS AND STRENGTH OF ROCK WITH DOUBLE FLAWS BASED ON STRAIN LOCALIZATION

Cracks in rock will initiate，propagate and coalesce under loading，which remarkably influences the strength and damage property of rock. Based on a DIC system which was proved reliable，uniaxial compression experiments were carried out on the specimens with two precast flaws. The strain field and strain localization of the whole specimen were obtained. It was found that the strain localization and the progressive damage were very distinctive in the test. The strain localization zone appeared in the initial phase governed the range and trend of the whole process of the strain field development. There were four failure modes found in the test，that is the non-coalescence mode，the coalescence mode at inner tip of flaws，the coalescence mode at outer tip of fracture and the inner-outer tip coalescence mode. The bridge angle and the arrangements of flaws had the effect on the formation of strain localization zone in mesoscopic level and determined the cracking path and the failure mode in macroscopic level. The coalescence of strain localization zone in the bridge area resulted in a fluctuation of stress-strain curve before the peak and reduced the peak strength. The slower the coalescence of the strain localization zones，the higher the peak strength.