Abstract:
Objective During the long-term service of geotechnical structures in cold regions, rock masses undergo continuous mechanical deterioration under freeze-thaw cycling. Because engineering rock masses are generally subjected to in-situ stress, the coupled effects of stress and freeze-thaw cycles on rock mechanical behavior remain unclear.
Methods Sandstone was selected as the test material, and laboratory tests were conducted under different axial stress levels and numbers of freeze-thaw cycles. An improved compact apparatus capable of real-time axial-stress monitoring during freeze-thaw cycling was developed, enabling continuous acquisition of the mechanical response of rock during the freeze-thaw process. After multiple freeze-thaw cycles under preset axial stresses, the specimens were subjected to ultrasonic wave-velocity testing and uniaxial compression tests. The stress-time response, stress-strain behavior, wave-velocity evolution, and peak-strength variation of sandstone under different conditions were systematically analyzed.
Results The results show that: (1) with increasing freeze-thaw cycles, the bearing capacity, peak strength, elastic modulus, and ultrasonic wave velocity of sandstone all decrease gradually; (2) under the same freeze-thaw conditions, applied axial stress increases the peak strength of sandstone and effectively slows the deterioration rate of wave velocity. After 40 freeze-thaw cycles, the peak strength of the rock specimens increased from 18.75 MPa in the unstressed state to 20.21 MPa under an axial stress of 6 MPa; (3) as the stress level increases, its modulating effect on sandstone becomes more pronounced, further controlling the damage degree and mechanical deterioration rate of sandstone during freeze-thaw cycling.
Conclusions This study reveals the regulatory effect of stress on sandstone damage evolution during freeze-thaw cycling and provides a scientific basis for freeze-thaw-resistant design and geological-hazard prevention in sandstone rock-mass engineering in cold regions.
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