Decay function and damage strain model of fresh sandstone subjected to freeze–thaw cycles.

Freeze–thaw cycle is one of the primary rock physical weathering agents which causes the deterioration and softening of rocks in cold regions. The frost-weathered rocks are prone to damage and destruction under loading. Determining the deterioration and stress–strain behavior of rocks following cyclic freezing and thawing is of crucial importance for evaluating the stability of rock excavation engineering in cold regions. A long-term artificial freeze–thaw cycles test on fresh sandstone samples was designed in this paper. The saturated condition was selected to accelerate the effect of freeze–thaw weathering. The mechanical behavior of the specimens undergoing different freeze–thaw cycles was further investigated through the uniaxial compression test. Experimental results indicate that the cycling of freezing and thawing causes a gradual decline in uniaxial compression strength followed by a rapid fall. An obvious beginning compaction stage can be observed in the stress–strain curve and the strain of the compaction stage increases during the freezing and thawing process. The deterioration of the sandstone was expressed by uniaxial compression strength, elastic modulus, and frost resistance coefficient in a piecewise decay model. A damage critical point can be distinguished in the model. Then, piecewise damage strain equations under the combination of freeze–thaw action and loading were derived by introducing the damage mechanics theory. The presented model was validated by the test results in this paper and a published article. It demonstrates that the simulated data agree well with the test results, indicating the effectiveness of the presented model in describing the stress–strain behavior of sandstone suffering long-term freeze–thaw weathering. [ABSTRACT FROM AUTHOR]