冻融作用引起裂隙岩体的损伤破坏是导致一系列工程冻害的重要原因。随着人类活动不断向高寒、高海拔地区推进，工程建设将会面临更多的裂隙岩体冻融损伤诱发的灾害问题。裂隙水在冻结过程能否形成冻胀力（即形成冰楔）以及冻胀力如何演化，是决定冻融损伤是否产生的关键前提。为了深入揭示含水裂隙岩体冻融损伤机制，本文以含不同深度裂隙的灰岩为研究对象，实时监测了冻融过程中裂隙水的温度场变化、冰楔的形成过程、冻胀力及冻胀变形的演化过程；同时研究了裂隙深度、裂隙含水量、冻结速率等关键因素的影响；结合冰楔作用下裂隙扩展过程中声发射信号的变化，及对裂隙扩展过程和扩展形态的细观观测结果，讨论了裂隙扩展规律，揭示了其力学开裂机制。主要得到以下几个结论：

1.冻融过程裂隙水的温度变化具有明显的阶段性。不同位置裂隙水在冻结过程均有明显的潜热释放和热弛豫现象；温度场及核磁共振成像结果表明外部裂隙水先发生冻结。冻融过程中冻胀力和冻胀变形演化可分为5个变化阶段，冻结过程中冻胀力萌生出现在水冰相变后期，裂隙中心位置产生的冻胀力值最大。

2.不同裂隙深度、裂隙含水量、冻结速率下裂隙内部的温度变化、冻胀力演化、裂隙端部变形表现出相似的变化规律。其中峰值冻胀力的大小受到的影响最大，随冻结速率的降低初始结冰时间点后移，裂隙深度越深冻胀变形越大，含水率越低热弛豫时间越短。

3.随着冻融次数增加冻胀力的萌生和释放速率增加，而最大冻胀力总体呈下降趋势。声发射信号值的突变与冻胀力演化的关键节点在时间上相对应；通过三维定位结果可以准确地捕捉到裂隙水结冰的动态变化和裂隙的扩展过程。不同深度裂隙的扩展路径不是单一不变的，冰楔作用下裂隙的扩展表现为典型的I型断裂。

4.裂隙上部密封条件的形成是冻胀力产生的前提条件，密封条件的形成主要有两种类型：一是冰塞向两侧拉裂后挤出的未冻水重结晶形成密封条件；二是冰塞向上移动两侧冰层拉断后未冻水向两侧迁移重结晶形成密封条件。

5.裂隙端部开裂后，冻融过程中新生裂隙内部的水（冰）首先冻结（融化）产生（消散）冰压力。裂隙冰中间会和裂隙端部形成贯通的断裂面，融化时融水会沿着断裂面向外渗流。冻融循环过程断裂面上的颗粒碎渣的脱落会加速裂隙的扩展。

本文揭示了冻融过程中含水裂隙内部温度、冻胀力的演化规律，阐明了冰楔作用下岩体裂隙端部的扩展特性和力学开裂机制。本论文的研究结果对于指导寒区工程冻害防护具有重要的理论参考价值。

The damage of joint rock mass caused by freeze-thaw cycle is an important reason for a series of freezing damage. As human activities continues to advance to the alpine and high altitude areas, engineering construction will face more disasters caused by frost damage of joint rock mass. Whether the crack water can form frost-heaving pressure (forming ice wedge) during the freezing process and how the frost-heaving pressure evolves are the key processes to determine whether frost damage occurs. In order to further reveal the frost damage mechanism of water-bearing joint rock mass, this paper takes different depth of limestone as the research object. The temperature field of crack water, the evolution process of ice wedge, the evolution of frost-heaving pressure and frost-heaving deformation were monitored in real time during freeze-thaw process. The influence of key factors, such as crack depth, crack water content and freezing rate, was also studied. Based on the change of AE (acoustic emission) signals in the process of crack propagation under the action of frost wedging and the micro-observation results in the process and morphology of crack propagation. The law of crack propagation was discussed and the mechanical cracking mechanism was revealed. The main conclusions are as follows:

1. In the process of freeze-thaw, the temperature change inside crack water had obvious stages. The crack water at different locations had obvious latent heat release and thermal relaxation during the freezing process.The results of temperature field and nuclear magnetic resonance imaging showed that the external crack water froze first. The evolution of frost-heaving pressure and deformation could be divided into five stages during freeze-thaw cycle. During the freeze process, the frost-heaving pressure initiation appeared in the late phase of water-ice phase transition, and the value of frost-heaving pressure generated in the center of crack was the largest.

2. The change of temperature, the evolution of frost-heaving pressure and the deformation of crack tip showed similar variation rules under different crack depth, crack water content, freezing rate. It was found that the peak frost-heaving pressure was the most affected. The decrease of freezing rate made the time point of water-ice phase transition move back. The deeper the crack depth, the greater the deformation of the crack tip, and the lower the water content, the shorter the thermal relaxation time.

3. With the increase of the number of freeze-thaw cycles, the initiation and release rate of frost-heaving pressure increased, the maximum frost-heaving pressure generally showed a downward trend. The abrupt change of AE signal value corresponded to the evolution of frost-heaving pressure at the time point. The dynamic process of crack water icing and the expansion and evolution process of crack tip can also be accurately captured by the 3D positioning results. The expansion path of crack with different depths was not single and constant, the fracture propagation under of frost wedging showed a typical type I fracture.

4. The formation of sealing conditions on the top of the crack is the premise for the generation of frost-heaving pressure. The forming of sealing conditions mainly have two types: one is that the unfrozen water extruded after the ice plug was cracked to the two sides recrystallized to form sealing condition; The other is that the ice plug moved upward and the unfrozen water migrated to both sides and recrystallized after the ice was pulled off, forming sealing condition.

5. After the fracture at the crack tip, the water (ice) inside the new crack in freeze-thaw cycle first froze (thawed) and produced (dissipated) ice pressure. A penetrating fracture surface was formed in the middle of the crack ice, which was connected to the newly fractured crack, and the meltwater will flow outward along the new crack during thawing. During freeze-thaw cycle, the shedding of particle on the fracture surface will accelerate the crack propagation.

This paper reveals the evolution law of internal temperature and frost-heaving pressure of water-bearing joint rock mass during freeze-thaw process, and expounds the expansion characteristics and mechanical cracking mechanism of joint rock mass under frost wedging. The research results of this paper have important theoretical reference value for the guidance of freezing damage protection in cold area engineering.

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