The damage strength of freeze-thaw rock provides an important reference for stability evaluations used during rock engineering in cold regions. In this paper, real-time acoustic emission tests of saturated sandstone are performed after various freeze-thaw cycles to study the uniaxial compressive strength and deformation characteristics of the resulting materials. The macro-meso damage evolution law of loaded sandstone is studied under the action of freeze-thaw cycles. The results show the following: (1) The saturated water absorption of sandstone increases, the peak strength and elastic modulus loss rates of sandstone increase linearly, and the frost resistance of the rock decreases with the number of freeze-thaw cycles. The sandstone failure mode gradually shifts from splitting failure to complex splitting shear failure of the failure surface. (2) If fewer than 10 freeze-thaw cycles are applied, the ring count signals at the compaction stage and after the peak strength is reached are extremely weak under a uniaxial compression load. With additional freeze-thaw cycles, damage inside the rock accumulates gradually, and the ring count signal appears during the rock compaction stage, fluctuates up and down, and continues until the peak strength is reached. When the compressive strength reaches its peak, the ring count intensity signal increases suddenly, and the frequency is high. After the strength reaches its peak, the acoustic emission signal shows that the rock sample still has some residual strength. As the number of freeze-thaw cycles increases, the cumulative ring count of sandstone gradually changes from the jumping stage to gradual growth. The acoustic emission characteristic parameters and ring count reflect damage to and expansion of freeze-thaw sandstone. (3) The cumulative extent of rock damage reaches the threshold value under loading and increases linearly until the rock is destroyed. When more freeze-thaw cycles are used, the time required for the rock to reach this threshold value is shorter, and the time required for sandstone damage is reduced gradually. These results provide a reference for the study of freeze-thaw damage and rock stability in cold regions.

The impermeable engineering surface layer in the cold regions blocks the water and heat exchange between the foundation soil and the atmospheric environment. Especially in cold areas with significant temperature differences, the moisture in the foundation soil accumulates at the bottom of the structure layer to form a covering effect. This will exacerbate the occurrence of engineering freeze-thaw diseases. This paper conducts a disease survey of the Guanshan oil and gas station site, which is located in a seasonally frozen soil zone. The ponding and freeze-thaw diseases under the concrete cover are analyzed. The formation process of the pot covering effect in the lower part of the concrete surface layer was reproduced through indoor tests. In addition, a water-vapor-heat coupling model of unsaturated soil was established, which quantitatively produced the formation process of silty clay covering under the concrete slab. The results show that (1) in-situ monitoring demonstrated that the water content of the roadbed soil from 0 to 50 cm below the concrete slab gathered significantly, with the water content increasing by 5 to 30%. (2) Under the action of the indoor time-varying covering effect, the moisture content of silty clay will increase with the number of freezing-thawing cycles, with a maximum migration amount of 6%. (3) Seasonal temperature changes lead to the accumulation of water in the subgrade surface, and the maximum accumulation amount is 32%. (4) During the freezing period, the liquid water and vapor water in the subgrade migrate to the surface layer of the subgrade. As a result, the moisture content of the subgrade surface layer increases, while the melting period is the opposite. The above research results can provide theoretical support and scientific countermeasures for engineering design and disease control in cold regions.