岩石卸荷力学行为与边坡开挖卸荷效应基础研究

Under the condition of unloading, rock exhibits totally different mechanical behavior from that under the condition of loading. The excavation of rock slope is a typical unloading engineering issue. Based on a typical excavation engineering of open-pit mine rock slope, the methods such as site investigation, laboratory test, numerical simulation and theoretical analysis, are used to conduct the research on the rock mechanical behavior and excavation unloading effect of rock slope under the condition of unloading. Firstly, the method of site investigation is used to obtain the spatial form of slope and macro-meso structure feature of rock mass. The meso analysis model of rock, which can reflect the structure feature and distribution law of actual mineral grain, is constructed by particle flow theory, and simultaneously, the loading-unloading method of meso analysis model and dynamic monitoring method of characteristic parameter for acoustic emission and energy are established. Then, based on the unloading mechanical test and meso simulation reuslts, the damage evolution law, meso mechanism and size effect of rock under the condition of unloading is investigated. On the basis of that, the continuum user-defined constitutive model, which can represent the mechanical characteristics of engineering rock mass under the condition of unloading, is constructed. Finally, based on the research results of rock unloading mechanical behavior, the excavation unloading effect and failure mechanism of rock slope with fluid-solid coupling under the condition of unloading is investigated, and the classification method of unloading area and degree for rock slope is established. To sum up, the research results can be function as a theoretical reference for the stability research of rock slope such as open-pit mine slope.

岩石在卸荷条件下表现出的力学行为与加载条件下的完全不同，而岩质边坡开挖便是一种典型的工程卸荷问题。结合典型露天矿山岩质边坡开挖工程，采用现场调研、室内试验、数值模拟和理论分析相结合的方法，对卸荷条件下岩石力学行为与岩质边坡开挖卸荷效应进行研究。首先，调查岩质边坡空间形态及岩体宏-细观结构特征，基于颗粒流理论构建具有实际矿物颗粒结构特征及分布规律的岩石细观分析模型，建立对岩石细观分析模型加卸载及声发射、能量等特征参量探测的动态监控方法；然后，结合卸荷力学试验及细观仿真结果，探寻卸荷条件下岩石损伤演化细观机理及尺寸效应，构建能表征卸荷条件下工程岩体力学特性的连续性自定义本构模型；最后，基于岩石卸荷力学行为研究结果，探究开挖卸荷条件下流-固耦合作用边坡开挖卸荷效应及其破坏机理，建立岩质边坡卸荷区域、卸荷程度的划分方法。研究成果最终可为露天矿山等岩质边坡稳定性研究及滑坡防治提供理论依据。

岩质边坡开挖卸荷，常常导致岩体损伤破坏，从而诱发滑坡事故。针对该科学问题，本项目采用了现场调研、理论分析、室内试验及数值模拟相结合的方法，开展了岩质高边坡开挖卸荷损伤机理研究。首先，设计并开展了岩石加卸载试验，研究了加卸载条件下岩石力学特性；然后，基于颗粒流理论及PFC程序，建立了具有岩石矿物结构特征的细观分析模型，并基于该模型开展了边坡岩体多尺度力学行为研究；最后，根据现场勘测资料，建立了具有实际结构面空间分布特征的边坡细观分析模型，并开展了实际边坡开挖过程的数值分析，从宏细观角度研究了边坡开挖卸荷条件下的损伤滑坡机制。本项目主要研究结论如下：.(1) 在三轴卸荷试验中，岩石试件的变形表现为沿卸荷方向的强烈扩容或膨胀，岩石的破裂体系较加载试验更为发育，其破坏程度也更为严重一些。在单侧限加载卸荷试验中，岩体表现出板裂化现象，裂纹形态大致可划分为5种类型。.(2) 采用平面黏结接触模型构建能反映矿物颗粒结构特征的边坡岩石细观分析模型，具有合理的拉压比性质，能再现岩石在单轴拉伸、单轴压缩、三轴压缩条件下的拉伸、劈裂、剪切等破坏模式及非线性特性。随岩体尺寸的增加，其单轴抗压强度、弹性模量逐渐降低，而尺寸效应和各向异性逐渐减弱。.(3) 顺层边坡开挖卸荷计算表明，滑坡产生的微破裂主要从坡底断续节理端部开始产生，逐渐向坡体上部发展；滑体底部形态较为平直，而后部形态较为曲折并呈台阶状破坏；滑坡产生的破碎颗粒体先在边坡面中、下部产生，其体积相对较小，随后在边坡上部产生，其体积相对较大。