龙游古洞室群围岩的温湿度疲劳效应及顶板开裂机制

Temperature and humidity around shallow cave have direct influences on mechanical behaviors of rock masses, and their periodic changes in scales of season and year can induce fatigue failures of the rock masses. Previous studies were mostly focused on laboratory testing of rock samples in conditions of single factor with short period, with few attentions paid to long-term effects of double factors. Moreover, no quantitative study has been found in literature for a breakthrough point starting from differences of deformations and failures between ancient caves. In the present project, Longyou Ancient Cave Group is chosen as investigation field. Based on roof deformation measurements of more than 7 years, environmental data in caves, and rock sample testing of temperature and humidity-induced effects, the project will be conducted for temperature and humidity-induced fatigue effects in rock masses around Longyou Ancient Cavern Group and roof cracking mechanism. The study includes: 1) Laws of periodic changes and spatial distribution of temperature and humidity in rock masses around ancient cave; 2) Physical and mechanical features and temperature and humidity-induced effects of argillaceous siltstone; 3) Dynamic model of temperature and humidity-induced effects of the cave, and fatigue-induced degradation mechanism of the rock masses; 4) Roof cracking mechanism and instability based on temperature and humidity-induced effects. Above study is not only helpful to clarify the differences between deformation fluctuation, cracking evolution, collapses and instability of roof, and increase level of quantitative long-term stability evaluation of caves. The project has great significances in practice.

对于浅埋洞室来说，温湿度环境不仅直接影响着围岩力学特性，相应的季节-年尺度周期变化还可以导致岩体的疲劳破坏。以往多为单一因素短期作用下的实验室岩样测试，基于二者联合作用下的长期效应研究很少，将大型古洞室群长期变形破坏差异作为切入点的定量研究还没有报道。以巨厚层泥质粉砂岩中的龙游古洞室群为研究对象，借助7年多的顶板变形观测数据、洞室环境信息及岩样温湿度效应测试，拟开展浅埋古洞室围岩的温湿度疲劳效应及顶板开裂机制的研究，具体内容包括：（1）古洞室围岩温湿度的周期性变化规律及空间分异性特征；（2）泥质粉砂岩样品的物理力学特征及温湿度效应；（3）古洞室围岩的温湿度效应动态模型及疲劳劣化机制；（4）基于温湿度疲劳效应的顶板开裂机制和失稳机理。相关研究成果不仅有助于揭示洞室温湿度环境导致的顶板变形波动、顶板开裂、垮塌失稳等变形破坏差异，还将提高洞室长期稳定性定量评价的研究水平，有着重要的实际意义。

对于浅埋洞室来说，温湿度环境不仅直接影响围岩力学特性，相应的季节-年尺度周期变化还可以导致岩体的疲劳破坏。以往多为单一因素短期作用下的实验室岩样测试，基于二者联合作用下的长期效应研究很少，将大型古洞室群长期变形破坏差异作为切入点的定量研究还没有报道。本项目以巨厚层泥质粉砂岩中的龙游古洞室群为研究对象，开展了浅埋古洞室围岩温湿度疲劳效应及顶板开裂机制研究，包括古洞室围岩温湿度的周期性变化规律、泥质粉砂岩样品物理力学特征、温湿度疲劳效应、古洞室围岩稳定性及顶板开裂机制。.在本项目的资助下，取得了以下重要结果和数据：（1）通过开展泥质粉砂岩的室内温湿度循环试验，分析了温湿度循环对试样的质量损失率、吸水率变化、表观裂隙及破裂形式等的影响，证明了温湿度循环作用对泥质粉砂岩有较强的疲劳劣化效应。（2）基于离散元颗粒流数值模拟方法，分析了不同循环次数下泥质粉砂岩的细观力学特征，温湿度循环不仅降低了泥质粉砂岩的抗压强度，还使其脆性降低、塑性增强，表现出较强的疲劳劣化效应。（3）联合平行黏结模型和光滑节理模型构建了含层理砂岩数值样品，通过单轴、三轴和直接拉伸测试对模型的微观参数进行了严格标定，并证明了在该参数条件下模拟的抗弯强度和直接拉伸强度具有良好的对应关系。（4）基于层理砂岩模型系统研究了层理面倾角、力学性能和间距对砂岩变形特征、抗弯强度和微破裂演化等三点弯曲力学行为的影响，揭示了层理面控制龙游石窟泥质粉砂岩顶板破坏的机制。（5）牛场1号洞的FLAC3D数值分析表明，洞室顶板岩体的分层可以大大提高直接顶的拉应力集中程度，层面的止裂效应和层间粘结效应是控制顶板裂缝数量和分布特征的关键因素。.相关研究成果不仅有助于揭示洞室温湿度环境导致的顶板变形波动、顶板开裂、垮塌失稳等变形破坏差异，还将提高洞室长期稳定性定量评价的研究水平，有着重要的实际意义。