Experimental Study on Mechanical Properties of Freeze‐Thaw Damaged Red Sandstone under Combined Dynamic and Static Loading

Abstract

Using the freeze-thaw cycle test chamber, the red sandstone samples are subjected to cyclic freeze-thaw tests. The physical properties, static mechanical properties of freeze-thaw damage rocks, and the compressional wave velocity at specific axial pressure are measured using conventional physical tests and uniaxial compression tests. The mechanical properties of freeze-thaw damage rocks under dynamic and static loading were studied using Hopkinson pressure bar which can exert axial pressure. The studies show that, with the increase of freeze-thaw cycles, the surface layer of the rock sample undergoes spalling phenomenon, the weight gradually decreases, the sample compactness becomes worse, there are microcracks between the cemented particles, and the compressive strength and elastic modulus decrease. Under the static loading, the longitudinal wave velocity of freeze-thaw damaged samples change significantly compared with that of samples without freeze-thaw. The freeze-thaw damage degree, axial pressure, and strain rate are coupled with each other, which together affect the dynamic mechanical properties of samples, and make the variation of mechanical parameters, such as dynamic peak strength and dynamic elastic modulus of rock. The combined action of freeze-thaw damage and axial pressure weakens the strain rate effect of samples, but when the incident wave of SHPB test is same, the dynamic strength and elastic modulus of freeze-thaw damaged samples are reduced compared with those without freeze-thaw. Combining with strain equivalence principle, the constitutive relation of freeze-thaw damage of red sandstone under dynamic and static combined loading can reflect the influence of coupling damage of axial pressure and freeze-thaw, dynamic impact parameters, and other factors, which are in good agreement with the test results.

Machine Learning Algorithms in Rock Strength Prediction: A Novel Method for Evaluating Dynamic Compressive Strength of Rocks Under Freeze-Thaw Cycles

“…DCS of rocks was determined using Hopkinson separated compression rods, with confining pressure gradients of 0, 2, 5, and 10 MPa, and an impact pressure range of 0.2 to 0.6 MPa. This paper conducted intelligent prediction research based on ten influencing factors affecting the DCS of rocks under freeze-thaw cycles [28,[47][48][49][50][51] , including FTC, CP, IP, DD, NWC, WA, ADW, P, PWV, and SR. After thorough investigation, this study amassed a total of 216 sets of data for the training and testing sets. The ratio between the training and testing sets was established at 8:2, with the initial 173 groups designated as training samples and the final 43 groups allocated for testing.…”

Energy evolution and crack development characteristics of sandstone under freeze-thaw cycles by digital image correlation

“…Li et al [ 3 ] performed uniaxial compression tests on granite with freeze-thaw cycles, and found that the mass of granite increased and the uniaxial compressive strength decreased after freeze-thaw cycles. Mei et al [ 4 ] studied the static and dynamic mechanical properties of freeze-thaw eroded red sandstone using uniaxial compression and Hopkinson pressure bar tests, and concluded that the static and dynamic strengths of freeze-thawed specimens were significantly lower than those of unfreeze-thawed ones. The physical and mechanical parameters of rocks can directly reflect the failure degree of freeze-thawed rocks, but if the change of physical and mechanical properties is the only consideration, the process of rock failure would be ignored.…”