类岩石材料有序多裂纹体单轴压缩破断试验与翼形断裂数值模拟

为研究断续岩石裂纹产状特性对岩体强度的影响和岩桥破断规律,在水泥砂浆中预制有序多裂纹体,开展单轴压缩下类岩石材料有序多裂纹体破断试验。研究发现：有序多裂纹体破断模式主要为排间翼形拉裂纹贯通、排间拉伸—剪切裂纹贯通和排内倾斜剪切裂纹贯通。当裂纹倾角较小（如倾角为25°和45°）时,随裂纹密度的增加,试件表征峰值强度总体上呈衰减趋势,而残余强度总体上呈增加走势；裂纹倾角较大（如倾角为75°和90°）时,裂纹密度对表征峰值强度无显著影响,其残余强度特性表现不明显；相同裂纹密度下倾角从25°变化到90°,试件表征峰值强度总体上呈增加趋势。提出主控岩桥贯通模式的概念,倾角25°试件的主控岩桥贯通模式大都是斜对角线上排间拉伸-剪切裂纹贯通；倾角45°试件的主控岩桥贯通模式为：翼形裂纹贯通和斜对角线方向上共面次生剪切裂纹贯通两种模式。裂纹尖端应力-应变集中特性揭示了压剪裂纹尖端的拉应变集中是岩石翼形裂纹萌生的本质原因,而裂纹端部的双向压应力-应变集中导致次生剪切裂纹萌生。从岩石断裂力学基本理论出发,引入点剪切安全系数,构建基于ANSYS的岩石多裂纹体翼形断裂扩展的数值分析模型,阐明了单轴压缩下有序多裂纹体翼形断裂贯通的力学机制,其数值结论与物理试验基本相吻合。

Fracture experiments on ordered multi-crack body in rock-like materials under uniaxial compression and numerical simulation of wing cracks

In order to study the rules of rock bridge rupture and the influences of occurrence characteristics of intermittent cracks on strength of rock mass, ordered multi-crack bodies are made using cement mortar. Fracture failure experiments on ordered multi-crack body under uniaxial compression are conducted. It is concluded that the transfixion pattern of wing tensile cracks, transfixion pattern of tension-shear cracks between different rows and oblique shear crack transfixion pattern in the same row are the main rapture modes for the ordered multi-crack body. The representative peak strength of specimens decreases with the increasing number of cracks. When the crack angle is small, such as 25°and 45°, the residual strength increases. While the crack angle is large, such as 75°and 90°, the crack density has little effect on the representative peak strength of specimens, and the characteristics of residual strengths are less evident. When the crack density is constant, the representative peak strength of specimens shows an increasing trend when the crack angles change from 25°to 90°. The pattern of main control crack coalescence is proposed. The transfixion of tension-shear cracks between different rows along the clinodiagonal is the pattern of the main control crack coalescence when the angle is 25°. While the crack angle is 45°, the patterns of the main control crack coalescence include two types, which are transfixion of wing cracks and transfixion of coplanar secondary shear cracks along the clinodiagonal. The characteristics of stress-strain concentration in crack tip reveal the fact that the essential reason of initiation of wing cracks is the concentration of tensile strain at crack tip, while the state of biaxial compressive stress-strain concentration near the main