无充填岩体结构面力学特性的周期剪切劣化效应与机制研究

Strength degradation mechanism of rock joints subject to cyclic shear loading and its analysis model is basis for accurate assessment of rock engineering safety under seismic load. Using similar material, joint specimens with different wall strengths and unfilled and natural morphology features was prepared, and then a series of cyclic shearing and microscopic testing are performed under different normal stresses. Based on the tests results, degradation characteristics of peak shear strength during cyclic shear are studied. Meanwhile, mesoscopic damage and the evolution characteristics of asperities were analyzed with mesoscopic tests results. A spherical micro-generalized model is set up according to micro-contact mechanics theory, and the deterioration mechanism of microscopic stress states and mesoscopic damage characteristics of joint asperities are theoretically analyzed. Based on the comprehensive analysis of various results，the macro-mechanical properties of joints under cyclic shear loading are illustrated form micro-mechanism view. By comparing the results under different experimental conditions，a cyclic shear strength formula is given, which contains the normal stress, rock strength, cyclic shear displacement amplitude, cycle numbers. And finally, based on the Disturbed Concept State theory, the constitutive model of the unfilled and natural roughness rock joints under cyclic shear loading is proposed, which is verified to be efficient by experiments. These studies will be providing dynamic mechanical parameters and theoretical model for the safety analysis of large-scale rock engineering under strong earthquake.

岩体结构面在周期剪切荷载下的力学特性劣化效应与机制研究，是准确进行大型岩体工程地震安全评价的重要基础。本项目拟采用系统的室内实验，研究无充填天然岩体结构面的周期剪切强度劣化规律；采用细观测试方法，研究结构面周期剪切的起伏特征退化规律；并通过理论分析，揭示结构面起伏体微观力学状态决定细观破坏特征进而影响宏观起伏特征退化的关联机制。在此基础上，建立岩体结构面起伏特征退化与力学特性劣化之间的联系，从深层次上揭示周期剪切条件下结构面力学特性的劣化机理与演化机制，以及初始起伏特征、法向应力、壁岩强度、剪切幅值等因素的影响机理；提出基于岩体结构面天然起伏特征并考虑多因素影响的周期剪切强度退化预测模型和体现结构面起伏特征周期剪切累积破坏过程的本构模型。研究成果可以为地震荷载作用下的大型洞室和边坡安全性评价工作提供岩体结构面的动态力学参数和分析模型。

本项目研究采用系统的室内实验，对无充填天然岩体结构面的周期剪切强度劣化规律进行了深入研究；采用细观测试方法，研究结构面周期剪切的起伏特征退化规律；并通过理论分析，揭示结构面起伏体微观力学状态决定细观破坏特征进而影响宏观起伏特征退化的关联机制。在此基础上，建立岩体结构面起伏特征退化与力学特性劣化之间的联系，从深层次上揭示了周期剪切条件下结构面力学特性的劣化机理与演化机制，以及初始起伏特征、法向应力、壁岩强度、剪切幅值等因素的影响机理；提出基于岩体结构面天然起伏特征并考虑多因素影响的周期剪切强度退化预测模型和体现结构面起伏特征周期剪切累积破坏过程的本构模型。研究成果可为地震荷载作用下大型或重要岩体工程的动力参数获取、稳定性与安全性评价工作提供了力学参数和基础分析模型。