冻融环境与循环荷载耦合下砂岩多尺度劣化破坏演变机理研究

With the development and scale expanding of the hydraulic and hydro-power engineering in cold regions, there are many complex disasters in rock engineering caused by freeze-thawing cycles and cyclic loading. The multiscale damage evolution mechanism of rock with freeze-thawing cycles and cyclic loading coupling effects is a focus on new development in rock mechanics and engineering now. A series of uniaxial compression tests, uniaxial compression tests under cyclic loading and scanning electron microscopy tests are conducted for sandstone specimen with freeze-thawing cycles and cyclic loading coupling effects. Based on rock mechanics, the relations are established between the parameters about freeze-thawing cycles, loading and the parameters about strength, deformation and energy. The characteristics of cracks on meso-scale of sandstone with freeze-thawing cycles are quantitatively investigated with digital image processing technology, statistics and fractal. The deterioration mechanism of fatigue damage on macro-, meso-structure and the evolution rules of energy accumulation, transfer and release are revealed. The mechanical characteristics on macro-scope and the quantitative characteristics of cracks on meso-scope are well understood about sandstone with freeze-thawing cycles and cyclic loading coupling effects. Combined with rock mechanics, fracture mechanics, damage mechanics and micromechanics, the multiscale mechanics model of sandstone with freeze-thawing cycles and cyclic loading coupling effects is established through the principle of energy dissipation. It is very important for the correct understanding about the fatigue failure mechanism of rock in cold regions and for the scientific evaluation of engineering stability.

随着寒区水利水电工程的开展及规模的扩大，冻融环境与循环荷载共同作用致使岩体工程灾害频发。冻融环境与循环荷载耦合下岩石多尺度劣化破坏演变机理问题成为当今国际岩石力学与工程研究的前沿课题。本项目通过对天然砂岩试样进行冻融循环试验、单轴压缩试验、单轴循环荷载试验及切片电镜扫描试验的研究，基于岩石力学理论，在宏观尺度上确立冻融参数、荷载参数与强度、变形、能量指标之间的关系；并采用图像处理技术、统计学及分形学，在细观尺度上定量描述冻融砂岩微裂纹损伤特征，揭示冻融砂岩宏观、细观疲劳劣化机理和损伤演化过程中能量积聚、传递与释放的规律，深刻认识冻融砂岩疲劳破坏的宏观力学特点和细观裂纹量化特征；进而结合岩石力学、断裂力学、损伤力学及细观力学，运用能量耗散原理，建立冻融环境与循环荷载耦合下砂岩多尺度力学模型。研究成果对正确认识寒区岩体疲劳破坏机理具有重要理论指导意义，为科学评价岩体工程稳定性提供重要依据。

冻融环境中岩石力学特性的变化规律已经成为当今国际岩石力学与工程领域的重要研究课题。本项目以新疆某地区砂岩为研究对象，基于冻融循环荷载试验、单轴压缩试验、三轴卸荷试验及切片电镜试验，采用宏观试验与细观试验相结合、理论分析与试验研究相结合的方法，对砂岩在不同冻融循环条件下的单轴压缩特性、卸荷力学特性及裂纹发展特性进行研究，探讨了砂岩在冻融循环和各类荷载作用下的应力应变曲线、变形指标、强度指标、破坏特征及细观尺度裂纹特征的变化，分析了砂岩在冻融循环荷载作用下的变形与强度变化规律，从宏观和细观两个尺度阐述了砂岩劣化破坏机理，在此基础上，以宏观试验数据和连续损伤介质理论为基础，建立了冻融循环过程中砂岩的本构模型。本项目的研究成果从宏观与细观两个层次分析了砂岩力学性质、细观结构与冻融循环之间的关系，揭示了砂岩在冻融环境中受荷破坏劣化机理，进一步完善了冻融岩石力学理论体系，为相关工程的安全性设计奠定了基础。