极地等高寒地区地表岩石经历各种风化作用，其中因温度变化产生的热应力循环和冻融循环是最常见且最具破坏性的物理风化营力。极地恶劣气候所带来的温度循环使得岩石稳定性必将遭受很大程度的影响，许多当地（例如基兹特因霍恩山-Kitzsteinhorn）的基础设施也将处于危险之中^[1]。同时随着“冰上丝绸之路”的开通，这种劣化影响严重阻碍了极地工程的建设。许多学者对于高寒地区岩石因年季温度改变产生的劣化损伤规律缺乏基础认识和科学依据，因此，本文研究大温差循环条件下花岗岩的损伤劣化规律与机制有着十分重要的意义。

本文选择干燥、饱和两种不同状态下的花岗岩为研究对象。测定其在特定温度循环次数后的质量损失、含水率、孔隙率、声学参数、电阻参数、热导系数、形貌特征等物理参数和单轴压缩强度、抗拉强度、断裂韧度等力学参数，总结花岗岩在大温差循环条件下的物理力学劣化规律。进一步通过细观实验观测其细观损伤发育规律，并结合数值模拟手段，区分热循环和冻融循环对花岗岩损伤劣化的影响，揭示大温差循环作用下花岗岩的损伤劣化机制。研究内容显示如下：

        （1）花岗岩在大温差循环条件下物理参数呈现不同变化规律。其中，干燥、饱和花岗岩的质量损失、含水率(饱和状态下测量并计算得出的结果)、孔隙率和表面粗糙度均随着循环次数的增多而增加。干燥花岗岩的纵波波速和电阻率随着循环次数的增多整体呈上升趋势，导热系数则呈现出与之相反的变化趋势；而饱和花岗岩纵波波速和电阻率则随着循环次数的增多而减少，导热系数呈先上升后趋于水平的变化趋势。

        （2）大温差循环作用对花岗岩力学特性同样具有显著的劣化效应。干燥、饱和花岗岩的单轴抗压强度、抗拉强度、断裂韧度变化规律具有较好的一致性，均随着循环次数的增加而发生不同幅度的减少。弹性模量、峰值应变、断裂能在此过程中具有不同的变化规律，其中弹性模量和断裂能随着循环次数的增加呈下降趋势，峰值应变则与之相反。单轴压缩试验过程中的声发射特征主要分为平静期和活跃期两个阶段，而在三点弯曲试验过程中则分为微裂隙压密闭合、微裂隙慢速稳定发展和微裂隙快速扩展这三个阶段。且随着循环次数的增多，花岗岩内部微裂隙密度增大，伴随着压缩过程中释放的弹性能量减小，振铃计数和累计振铃计数也逐渐减少。

        （3）大温差循环作用下干燥、饱和花岗岩裂隙发育规律同样存在差异。花岗岩在初始状态下矿物颗粒边界明显且存在少量微裂隙，不同矿物颗粒中间有孔洞等缺陷存在。随着循环次数的增加表面颗粒出现脱落现象同时裂隙进一步发育扩展。这种裂隙发育多为晶间裂隙。通过数字图像处理方法对花岗岩裂隙结构进行量化得出：饱和花岗岩大尺度裂隙数量、裂隙宽度、长度明显大于干燥花岗岩。在经历320次大温差循环后饱和花岗岩的平均面裂隙率、裂隙最大宽度和单位面积裂隙累积长度分别增大了105%、46%和133%；而干燥花岗岩裂隙发育则明显低于饱和试样，增幅仅为42.8%、22.1%和59%。

       （4）大温差循环条件下花岗岩损伤机制可分为热损伤和冻融损伤两大类。其中热损伤是由两种热应力所导致，分别为不同矿物成分膨胀收缩不一致和岩石内部温度梯度所形成的热应力。冻融损伤则由①体积膨胀理论②毛细管理论这两种损伤机制共同作用产生。其中体积膨胀理论的冻融损伤机制占主导地位。

The surface rocks in polar and high-altitude cold regions undergo various weathering processes, among which thermal stress cycles and freeze-thaw cycles caused by temperature changes are the most common and destructive physical weathering forces. The extreme polar climate causes temperature fluctuations, which will greatly affect the stability of rocks, and many local infrastructures (such as the Kitzsteinhorn in Austria) will also be at risk. [1]With the opening of the "Ice Silk Road," this degradation has seriously hindered the construction of polar engineering projects. Many scholars lack a basic understanding and scientific basis for the degradation and damage laws of rocks in high-altitude regions due to seasonal temperature changes. Therefore, studying the mechanisms of rock damage and degradation under conditions of large temperature differentials is of great importance.

This article focuses on two types of granite in dry and saturated states as research objects. Physical parameters such as mass loss, water content, porosity, acoustic parameters, electrical resistance, thermal conductivity, and morphological characteristics, as well as mechanical parameters such as uniaxial compressive strength, tensile strength, and fracture toughness, are measured after a specific number of temperature cycles. The physical and mechanical degradation laws of granite under large temperature difference cycles are summarized. Furthermore, the micro-damage development law is observed through microscopic experiments, and the influence of thermal cycling and freeze-thaw cycling on the damage degradation of granite is distinguished by combining numerical simulation methods, revealing the damage degradation mechanism of granite under large temperature difference cycles. The research content is summarized as follows:

Under large temperature differential cycles, the physical parameters of granite exhibit different patterns of change. Specifically, the mass loss, water content, porosity, and surface roughness of granite increase with the number of cycles. The longitudinal wave velocity and electrical resistivity of dry granite generally show an overall upward trend with the increase of cycle times, while the thermal conductivity shows the opposite trend. In contrast, the longitudinal wave velocity and electrical resistivity of saturated granite decrease with the number of cycles, while the thermal conductivity initially increases before trending towards a plateau.

(2) Large temperature difference cycles weaken the mechanical properties of granite. A consistent relationship exists among the mechanical properties of dry and saturated granite, such as uniaxial compressive strength, tensile strength and fracture toughness. These properties decline as the cycle times increase. The elastic modulus, peak strain and fracture energy exhibit different variation patterns under this effect. As the number of cycles increases, the elastic modulus and fracture energy decrease, whereas the peak strain increases. The acoustic emission (AE) characteristics can be classified into two stages in uniaxial compression tests.: a quiet stage and an active stage. In three-point bending tests, the AE characteristics can be divided into three stages: micro-crack closure under pressure, slow and stable development of micro-cracks, and rapid expansion of micro-cracks. As the number of cycles increases, the micro-crack density inside the granite increases. The elastic energy released during compression decreases, resulting in a reduction of both the AE ring count and the accumulated AE ring count. The accumulated AE ring count curve becomes smoother over time.

(3) Observations from microscopic experiments show that the development of fractures in granite follows a certain pattern at different scales. In the initial state, mineral particles in the granite are clearly visible and there are few microcracks along the boundaries of the particles, with defects such as pore holes in the middle of the mineral particles. As the number of cycles increases, fractures in the granite begin to expand and particles on the surface start to detach. These microcracks are mostly intergranular cracks. By using digital image processing methods to quantify the crack structure of granite, it is found that the number, width and length of large-scale cracks in saturated granite are significantly larger than those in dry granite. After 320 cycles, the average surface crack rate, maximum crack width, and accumulated crack length per unit area of in saturated granite increased by 105%, 46%, and 133%, respectively; while the crack development of dry granite was significantly lower than that of saturated samples, with an increase of only 42.8%, 22.1% and 59%, respectively.

(4) Under large temperature difference cycling conditions, granite damage mechanisms can be classified into two main categories: thermal damage and freeze-thaw damage. Thermal damage is induced by two types of thermal stress: differential thermal expansion and contraction among various mineral components, and thermal stress caused by the temperature gradient within the rock. Three mechanisms cause freeze-thaw damage: the theory of volume expansion, the theory of capillary suction, and the theory of frost heaving. Among these, the volume expansion theory plays a dominant role.