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采用室内试验和理论分析相结合的方法,对有厚度天然结构面的法向循环加载变形特性进行研究。研究的天然结构面属平直稍粗型,厚2~3 mm,层间充填以岩屑为主,夹少量泥,母岩为灰岩。首先,对工程作用下的结构面应力演化过程进行梳理,并根据对结构面法向应力-闭合变形曲线特征的总结,设计了室内试验的法向荷载应力路径。其次,介绍了取样、基本物理和力学特性测试以及试件制备,分别开展了单次和多次法向加、卸载试验,并对试验曲线特征和法向变形力学机制进行分析。然后,对结构面法向循环加载本构关系进行研究,认为当法向应力在20 MPa以内时,分别采用双曲线模型和考虑修正参数的改进双曲线模型,可较好地模拟不同荷载阶段时的结构面法向应力-闭合变形关系;同时,发现当法向应力进入高应力区间后(定义大于20 MPa的应力为高应力,低于20 MPa的应力为中低应力),试验数据呈现新的特点,试验变形值与模型预测值的差距越来越大。最后,分析了造成差异的可能原因,认为在研究高应力条件下的结构面法向变形特征时,采用天然结构面试样是必要的。
The combination of laboratory test and theoretical analysis is used to study the normal cyclic loading deformation of a natural surface with thickness. The natural structure of the study is flat and slightly rough, 2 ~ 3 mm thick. The main filling is lithic debris, with a small amount of mud and the parent rock is limestone. Firstly, the stress evolution of structural plane under the action of engineering is combed, and according to the summary of the normal stress-closure deformation curve of structural plane, the normal load stress path of the indoor experiment is designed. Secondly, the sampling, basic physical and mechanical properties testing and specimen preparation are introduced. Single and multiple normal loading and unloading tests are carried out respectively. The characteristics of the test curve and the mechanics of normal deformation are analyzed. Then, the constitutive relationship of normal loading of structure plane is studied. It is concluded that hyperbola model and modified hyperbolic model considering correction parameters are respectively adopted when the normal stress is less than 20 MPa, which can simulate different loading stages , The normal stress-closure deformation relationship of the structural plane is found. At the same time, it is found that when the normal stress enters the high stress interval (the stress greater than 20 MPa is defined as high stress and the stress less than 20 MPa is medium-low stress) The difference between experimental deformation values and model predictions is getting bigger and bigger. Finally, the possible causes of the differences are analyzed. It is considered that it is necessary to use natural structural surface samples when studying the normal deformation of structural planes under high stress conditions.