中文摘要：

通过带加载SEM高温试验系统对含双预制缺口北山花岗岩进行原位观察热力耦合破坏试验研究。研究表明,北山花岗岩的矿物成分及花岗岩矿物颗粒粒径差异较大,这些矿物具有不同的热学和力学性质（或硬度）,这将大大影响花岗岩的破坏机制及断裂韧性,热开裂、力诱发微裂纹的萌生、扩展和贯通等受到热力耦合机制的综合影响,并且这些机制反过来也将影响其他的机制,如渗流场及化学场的变化。对于北山花岗岩I型断裂而言,裂纹的扩展主要受到与其垂直方向拉应力的影响,但试件较大的原生缺陷和较大矿物颗粒对花岗岩的断裂路径影响不容忽视。特别是随着温度的变化,花岗岩的断裂机制将发生变化,低温以沿颗粒（沿晶）断裂为主,而高温以沿颗粒（沿晶）和穿颗粒（穿晶）耦合断裂机制为主。试验表明,75℃之前花岗岩的平均断裂韧性约为4.728 MPa.mm1/2,而75℃之后的平均断裂韧性为3.048 MPa.mm1/2,前后断裂韧性降低了35%左右,这主要是因为温度的升高直接导致热开裂增多,且矿物颗粒之间的胶结作用明显减弱,这逐渐影响了花岗岩的断裂韧性,进而将影响其渗流场和化学场,可见高放核废料储库设计中温度的影响不容忽视。

英文摘要：

Abstract- In-situ experimental investigations on thermal-mechanical coupled effects on physical and mechanical behavior of Beishan granites have been carried out through high temperature scanning electron microscope（SEM） testing system. Studies have clearly indicated that both mineral composition and mineral particle size are quite different for Beishan granite; and they have different thermal and mechanical properties（or hardness）, which greatly affect the failure mechanism and fracture toughness of granite. Thermal cracking, the initiation, propagation and coalescence of microcracks are greatly affected by thermal-mechanical coupled mechanism. In addition, these mechanisms will in turn affect other mechanisms, such as variations of seepage and chemical fields. For model I crack sample of Beishan granite, the crack propagation direction is proximately perpendicular to the direction of tensile stress. In addition, the initial defects and larger mineral particles have also greatly affected the granite fracture path. Especially with the temperature changing, granite fracture mechanism will change from the boundary（intergranular） fracture mechanism at low temperature to the coupled mechanism of boundary（intergranular） and grain（transgranular） fracture. Experimental data also show that the average fracture toughness of Beishan granite before 75℃ is about 4.728 MPa. mm1/2, while approximately 3.048 MPa. mmv2 after 75℃, which deceases about 35%. The main reasons are due to the increasing thermal cracking with the increasing temperature and loads, which lead directly to the increasing microcrack and the decreasing cementation of mineral particles. All of these gradually affect the fracture toughness of granite. In addition, they will affect the seepage and chemical fields. Therefore, the thermal-mechanical coupling effects should not be ignored in nuclear waste repository design.