寒冷地区地下洞室岩体冻融微观损伤机理研究

The mechanical properties and degradation mechanism of rock under freezing-thawing conditions have become one of front direction concerned with rock mechanics field. In cold region mine, coupling effect of rock, water, temperature, ice, stress and other factors are leading to rock freezing-thawing degradation happen and disaster appear, and it has significant impact to underground engineering stability in cold regions. Considering the needs of underground cavern in cold regions and relies on the method of testing and theory analysis, Taking temperature field of fractured rock as main factors, this project finish the research works of underground engineering rock freezing-thawing degradation mechanism and evolution mechanism by NMR technology, The granite with freezing-thawing cycles were measured by NMR technology and the characteristic of NMR T2 distribution, porosity, T2 spectrum and magnetic resonance imaging were obtained. The porosity distribution characteristics and its variation features of granite under different freezing-thawing cycles condition were obtained. It has revealed the degradation evolution law of rock microstructure characteristic under different freezing-thawing condition. The freezing-thawing degradation models of granite were summarized out and the relationship curve between uniaxial compression strength and freezing-thawing cycles, modulus of elasticity and freezing-thawing cycles were obtained. The freezing-thawing degradation evolution equation of granite was build. Study the rock freezing-thawing degradation theory and evolution mechanism, the effect factors of rock freezing-thawing degradation and its disaster characteristics in cold regions engineering were analyzed too. Combined with the disaster chain theory, freezing-thawing disaster chain-effect and broken chain & disaster mitigation methods of mine in cold regions were discussed.

冻融条件下地下洞室岩体力学特性及损伤劣化机理一直是岩石力学领域关注的前沿方向。在寒区地下工程中，由于岩性、水分、温度、冰雪、应力等多重因素的耦合作用，导致岩石冻融损伤和冻融灾害的发生，对寒区地下工程的稳定性产生了重大影响。结合寒区地下工程需要，以室内实验和理论分析为基础，以作用于岩石的温度场变化为主要考虑因素，采用核磁共振技术对地下洞室岩体的微观冻融损伤机理和冻融损伤演化规律开展研究，获得不同冻融条件下岩石的T2谱分布、T2谱面积、核磁共振成像的变化特征和岩石微观结构，揭示冻融循环条件下寒区岩体的孔隙分布特征及变化特性；揭示冻融循环-大温差-环境荷载耦合作用下地下洞室岩体物理力学特性与岩体内部微观结构渐变劣化之间的关联规律；分析岩石冻融损伤的影响因素以及寒区地下洞室工程冻融灾害特征。结合灾变链式理论，进行寒区地下洞室岩体冻融灾害致灾链式效应分析和断链减灾对策研究。

冻融条件下地下洞室岩体力学特性及损伤劣化机理一直是寒区岩土工程技术领域关注的前沿方向。探索冻融环境下岩体的力学行为及其相关关键科学问题对认识寒区冻融环境下地下洞室的特性和应用具有重要的科学意义。.本项目以寒区引水隧洞工程为背景，以作用于洞室岩体的温度场变化为主要考虑因素，以寒区隧洞工程岩体为岩样在最低冻结温度为-40℃、融化温度为20℃的条件下对4组不同状态的岩样开展了冻融循环试验，并采用核磁共振技术和SEM 微观扫描技术对不同冻融循环次数的岩样进行了内部微观结构的损伤探测，获得了不同冻融条件下岩石的T2谱分布、T2谱面积、核磁共振成像的变化特征和岩石微观结构，获得了岩体内部微观孔隙结构的变化规律，揭示了冻融循环条件下岩体微观结构渐变劣化规律。同时，采用电液伺服高温高压岩石力学试验系统对冻融后的岩样进行了单轴加载、三轴压缩试验，揭示了冻融循环-环境荷载耦合作用下隧洞岩体物理力学特性与岩体内部微观结构渐变劣化之间的关联规律，探明了抗压强度、弹性模量与冻融循环次数的关系。.基于连续介质力学、热力学、渗流力学，考虑低温相变对岩体温度场和渗流场的影响，结合低温冻结条件下洞室围岩的温度场-渗流场耦合模型，采用有限元法对引水隧洞工程进行围岩的冻结过程分析，研究低温相变条件下隧洞围岩温度场和渗流特性的变化规律，对引水隧洞经受长时间持续冻结作用后的围岩温度场、渗流特征进行了分析。同时建立了低温冻融条件下岩体的温度-渗流-应力(THM)耦合模型，研究了低温冻融循环条件下洞室围岩冻胀力的变化规律，探明了经历不同冻融循环次数围岩衬砌结构的变形和受力特征。.结合灾变链式理论，对寒区洞室冻融灾害进行了致灾链式效应分析。根据寒区洞室冻融灾害特点，揭示了洞室冻融灾害的产生和控制机理，提出了一种新的引水隧洞的保温抗冻胀结构。项目研究成果对极端气候条件下寒区岩体工程安全评估和环境保护具有重要的工程意义和学术价值。