为了探究冻融循环作用对土体结构和力学性质的影响机理，以内蒙古元宝山露天煤矿内排土场典型黏土为研究对象，采用室内冻融循环试验和MatDEM数值模拟，进行土体内部温度场、水分场和应力场的模拟分析。结果表明：排土场土料经过冻融循环后发生冻缩现象；低围压时应力−应变曲线呈现应变软化型，发生剪切破坏，围压升高后向应变硬化型转变，发生剪胀破坏；抗剪强度的劣化受前3次冻融作用的影响最为显著，在第3次达到最低值；温度的传递过程可划分为温度快速下降、缓慢相变过程、继续降温、温度稳定4个阶段；水分运移主要在温度传递的前2个阶段发生，且第二阶段的水分运移量居多；颗粒受冻融作用后整体半径缩小、分散性增大；温度和水分运移引起的颗粒胀缩、冰−水相变、冷生结构的形成等，导致颗粒的大小、位置、连接状态和颗粒间的应力等反复变化，共同驱动土体产生不可逆的结构性损伤，进而造成强度劣化。水分运移不仅为冷生构造的生长提供水源条件，还产生溶蚀、冲刷破坏，与水的相变共同成为冻融循环作用导致土体发生结构调整和应力场变化的主要原因。通过离散元法模拟冻融循环，有助于了解土体内部的力学特征和强度劣化机理，为冻区露天煤矿内排土场边坡及其他工程建设的稳定性研究提供参考。

In order to investigate the influence mechanism of freeze-thaw cycles on the structure and mechanical properties of soil, the typical clay soil in the inner dump of Yuanbaoshan open-pit coal mine in Inner Mongolia was taken as the research object, and the simulation analysis of the internal temperature, moisture and stress fields of the soil was carried out through laboratory freeze-thaw cycle tests and MatDEM numerical simulation. The results show that: freeze-shrinkage occurs to the soil in the dump after the freeze-thaw cycles, and the stress-strain curve shows the trend of strain softening at low confining pressure for shear failure, and the trend of strain hardening at the increased confining pressure for dilative failure. The deterioration of shear strength was most significantly affected by the first three freeze-thaw cycles, and reached the lowest value in the third cycle. The temperature transfer process can be divided into four stages: rapid temperature drop, slow phase transition, continuous cooling and temperature stabilization. Moisture migration mainly occurs in the first two stages of temperature transfer, with more in the second stage. The overall radius of the particles decreases and the dispersion increases after freeze-thaw. The expansion and contraction of particles caused by temperature transfer and moisture migration, the ice-water phase transition and the formation of cryostructures lead to the repeated changes in particle size, position, connection state and interparticle stress, which together drive the irreversible structural damage to the soil, resulting in strength deterioration. Moisture migration not only provides water conditions for the formation of cryostructures, but also produces dissolution and erosion damage to them, which together with the phase transition of moisture is the main reasons for the structural adjustment and stress field change of soil under the action of freeze-thaw cycle. The simulation of freeze-thaw cycle by discrete element method is helpful to understand the mechanical properties and strength degradation mechanism of soil, and provides a reference for the stability study of dump slopes and other engineering constructions in open-pit coal mine in frozen areas.