干湿交替作用下泥质砂岩强度劣化机理及损伤本构关系研究

In the face of the long-standing cyclic drying-wettomg process in the wild, the microscopic properties of the porous materials such as rock, which is made of solid skeleton and pore space, must be changed. On that basis, its macroscopic mechanical properties can also be affected, for example, the strengh of rock is weakened and the deformation is damaged, and eventually it can lead to the decline of rock engineering stability and increasing of instability probability. However, the cognition insufficiency to the drying-wetting circulation effect of rock mechanical properties is a general problem,and which make the systematic research results from microscopic to macroscopic lacked seriously. In response to these scientific issues, taking the widespread argillaceous sandstone in Yunnan open pit mine as an example, through the the combining methods of macro tests and micro tests, experimental study and theoretical analysis, the evolution law of microstructure of argillaceous sandstone in the repeating drying-wetting alternation process is researched, and the influence degree of drying-wetting alternation to the mechanical behavior of argillaceous sandstone is discussed. On the basis of observing the response relationships between the macro and micro parameters of rock and the action degree of drying-wetting alternation, such as porosity, particle cementation patterns, deformation parameters, shear parameters and compressive strength etc., the strength weakening mechanism and damage evolution law of argillaceous sandstone under cyclic drying-wetting conditions are described, and its damage constitutive model considering drying-wetting cyclical effect is established. The research results will provide a theoretical foundation for the security design and parameters selected of relevant geotechnical engineering, meanwhile, which is also a useful complement and further improvement to the rock mechanics theory system.

面对自然界中长期存在的降雨与蒸发这一反复干湿交替过程，岩石这类由固体骨架和孔隙组成的多孔介质材料在微观特性上势必会产生相应改变，进而导致其宏观力学特性的劣化与岩体工程稳定性的下降。然而,当前对岩石的干湿循环效应还认识不足，缺乏从细微观到宏观方面系统性的研究成果。本项目针对上述科学问题，以云南露天矿边坡中广泛存在的泥质砂岩为研究对象，采用宏观试验和微观测试、试验研究和理论分析相结合的方法，研究反复干湿交替作用下泥质砂岩细微观结构发展演化规律，探讨干湿交替对泥质砂岩力学行为的影响程度，通过考察岩石孔隙率、颗粒胶结方式、变形参数、抗剪参数及抗压强度等宏微观参数与干湿交替作用程度之间的响应关系，系统阐明泥质砂岩强度劣化机理及其损伤演化规律，并建立考虑干湿循环效应的泥质砂岩损伤本构模型。研究成果将为相关岩土工程的安全性设计及参数选取提供理论依据，同时也是对岩石力学理论体系的进一步完善与有益补充。

复杂条件下岩石力学特性的变化规律一直是岩石力学领域重要的研究课题。该项目以砂岩为研究对象，采用宏观试验和微观测试、实验研究和理论分析相结合的方法，对砂岩在两种不同干湿循环条件下（15次和30次）的单轴压缩特性、剪切特性及三轴压缩特性开展了大量的室内实验，探讨了砂岩吸水率、质量损失率、应力-应变曲线、变形指标、抗压强度、剪切参数、破坏特征、声发射规律及围压效应等与干湿循环作用之间的关系，分析了砂岩在反复干湿循环作用下的变形与强度变化规律，阐释了砂岩强度劣化机理。在此基础上，基于连续损伤介质理论和神经网络方法，分别建立了砂岩在干湿循环条件下的本构模型，并得出了理论表达式。该项目的研究成果从更深层次上分析了砂岩微观结构、力学性质与干湿循环效应之间的关系，揭示了砂岩力学特性演化规律与强度劣化机理，促进和完善了岩石力学理论体系，为相关岩土工程的安全性设计及参数选取提供了理论依据。