库水作用下岸坡软岩强度恢复效应及其机理研究

Soft rock slope disasters occurred frequently under the action of reservoir water, the strength recovery of the soft rock has not yet been studied systematically, the mechanism of soft rock strength recovery is not yet clear, the current study of soft rock mechanics performance without considering soft rock strength recovery effect, result in the theoretical research of soft rock slope leg behind of engineering practice application. Taking mudstone of the three gorges reservoir slope as the research object, and mesoscopic damage development of pore structure in strength recovery process as the main line, the initial residual strength can be obtained by the shear test on the basis of hydraulic . environmental characteristics of reservoir slope. Based on nuclear magnetic resonance (NMR) technique, the mesoscopic pore structure characteristics can be obtained,which have gone through the hydraulic effect , and the shear test was conducted again to get the residual strength after the strength of soft rock recovered. Then combined with the results of mechanical test and microstructure test, the mechanism of soft rock self-healing was revealed. On the basis of experiment test and theory analysis, the soft rock strength change and the mesoscopic pore structure were associated, and a damage mechanics model was set up considering soft rock self-healing effect finally. Research results will help to deepen understanding the engineering properties of soft rock,which would be good supplement work of soft rock strength and damage, and provide theoretical basis for the effective prevention and control of slope disasters.

目前针对岸坡软岩力学性能的研究没有考虑软岩强度恢复效应，软岩强度恢复的机理尚不清楚，岸坡软岩产生强度恢复的机制也不明确，导致软岩控滑边坡的理论研究与工程实践应用相差较大。本项目以三峡库区边坡的泥岩为研究对象，以泥岩在强度恢复过程中细观孔隙结构损伤发展过程研究为主线，首先在分析岸坡软岩经历水力环境特点的基础上进行剪切试验，获得初始残余强度之后，基于核磁共振技术获取试样在经历不同水力作用前后的细观孔隙结构特征，并再次进行剪切试验测试其强度恢复后的残余强度；然后结合力学试验与细观测试的结果，揭示软岩自愈合的机理，阐明软岩产生强度恢复的机制；最后在试验测试与理论分析的基础上，量化软岩宏观力学特性与细观孔隙结构之间的关联关系，建立考虑软岩强度恢复效应的损伤力学模型。研究成果将有助于深化认识软岩的工程特性，补充软岩强度及损伤特性研究的不足，为软岩控滑边坡灾害的有效防治提供理论依据。

岩石在水岩作用下反应过程中细观结构的改变是导致其力学行为发生改变的根本原因。本项目首先整理了大量涉水岩质边坡中“损而未裂，裂而不滑”的案例，以典型的砂岩和泥岩地层构成的岸坡为研究对象，分析了岸坡岩体内部裂隙张开闭合与斜坡受水力作用之间的关系，基于现场原位测试结果提炼了岸坡岩体内部结构特征，初步分析了岸坡不同岩体结构与岸坡稳定性的关系，从宏观上描述了库区岸坡岩体的强度恢复效应；然后，根据库区岩体的赋存环境，分别设计了考虑水、应力、饱水-失水过程等多个因素的岩石试验方案，分析了不同条件变化对岩石强度（单轴、三轴或者点荷载强度）改变的过程，揭示了岩石产生强度恢复的条件及恢复机制，进一步基于矿物测试及细观结构测试分析了岩石产生强度恢复的机理；最后，分析库水的长期浸泡与周期性干湿循环作用对岩石结构、性质的影响，基于核磁技术研究了砂岩和泥岩经历不同水力作用过程对岩石孔隙结构的改变，阐明了岩石在非连续破裂过程中细观结构的演化规律，并将岩石的细观结构变化与岩石力学指标（黏聚力、内摩擦角、峰值强度）建立联系，初步构建了考虑岩石强度不确定性的非线性损伤力学模型。结果表明，水在矿物颗粒间的渗透运移作用、库水周期性运营形成的循环应力作用、岩石矿物骨架的水力稳定结构及充填颗粒的自组织行为，包括岩石矿物的种类等都是影响岸坡岩体强度恢复的主要因素，不同因素组合条件下岩石的强度恢复过程具有差异性和阶段性特征，这些特征可以通过岩石细观结构的改变进行捕捉，但与岩体宏观裂隙状态的对应关系还需要进一步探讨。项目资助发表核心及以上论文5篇，待发表论文2篇，授权专利1项，培养硕士生6名，其中3人已取得硕士学位，3名在读。项目投入经费26万元，支出24.5192万元，剩余经费1.4808万元，各项支出基本与预算相符，剩余经费计划用于本项目研究后续支出。