岩石拉-剪强度及损伤-断裂演化机理试验研究

The construction of large-scale infrastructure, such as hydroelectric, transportation and mining engineerings, often involves large-scale rock mass excavation. Such strong excavation and unloading results in the cataclysmic tension-shear failure of rock mass. However, there have been few studies on rock tension-shear test. There is short of the deep understanding of rock tension-shear failure mechanism and tension-shear strength criterion with physical significance. In this project, the tension-shear tests of various rocks will be carried out using the self-developed rock tension-shear device to study the rock tension-shear properties of deformation and strength and damage-fracture mechanism under different stress paths and load rates. The methods of acoustic emission, digital image correlation, electron microscopy, 3D laser scanning and numerical simulation will be used to reveal the damage-fracture evolution process of rocks under tension-shear stress. The method of quantitative representation of the fracture mechanical property of rupture surface by the tensile fracture ratio from microscopic scale will be established. The transition from tension to tension-shear and to shear fracture with the variation of stress state will be revealed. Using energy theory, the quantization correlation of rock damage-fracture evolution, tensile fracture ratio, and energy dissipation and release will be revealed under tension-shear stress, and a damage evolution equation and fracture criterion will be established. The rock nonlinear tension-shear strength criterion with physical parameters of tensile strength, pure shear strength and tensile fracture ratio will be constructed. The research results will innovatively enrich the basic theory of rock mechanics.

大型基础工程建设如山区水电、交通及矿山工程常涉及大规模岩体开挖，诸如此类强开挖卸荷易导致岩体灾变性拉-剪破坏。但以往岩石拉-剪试验研究很少，缺乏岩石拉-剪破坏机理深入认识和具有物理意义的拉-剪强度准则。项目采用自主研制的岩石拉-剪装置开展多种类型岩石拉-剪试验，研究不同应力路径和荷载速率下岩石拉-剪变形、强度等力学特性及损伤-断裂机理。综合声发射、数字图像相关技术、电镜扫描、三维激光扫描和数值模拟等方法，揭示拉-剪应力作用下岩石损伤-断裂演化过程，建立以拉-剪破裂面微观尺度拉伸断裂比定量评价其断裂力学性质的方法，揭示拉伸-拉剪-压剪破坏随应力条件的转换规律。结合能量原理，揭示拉-剪应力作用下岩石损伤-断裂演化及拉伸断裂比与能量耗散及释放的量化相关性，建立其损伤演化方程及断裂判据。构建以拉伸强度、纯剪强度及拉伸断裂比为物理参数的岩石非线性拉-剪强度准则。研究成果将创新性丰富岩石力学基础理论。

大型基础工程建设如山区水电、交通及矿山工程常涉及大规模岩体开挖，诸如此类强开挖卸荷易导致岩体灾变性拉-剪破坏。项目采用自主研制的试验装置，开展了法向拉应力作用下的直剪试验和围压作用下的直接拉伸试验，揭示了法向应力、围压以及加载速率对岩石拉-剪变形、强度等力学性质和破裂特征的影响规律。采用颗粒离散元数值模拟试验，揭示了损伤演化过程以及微观晶粒尺寸、不均匀性和矿物组成对破坏机制的影响规律。基于能量理论，揭示了损伤演化过程中能量的转化规律和断裂判据以及围压和加载速率对能量的影响规律。建立了考虑剪切速率的幂函数拉-剪强度准则和考虑包络线“外凸”现象的压-拉强度准则。建立开发了颗粒离散元平行黏结接触模型的幂函数强度准则和双抗拉强度参数的Mohr-Coulomb强度准则，有效解决了常规接触模型无法模拟强度包络非线性的缺陷。研究成果丰富了岩石力学基础理论，为岩体开挖工程的破坏机理及稳定性评价提供理论基础及技术支撑。