Study on Mechanical Properties and Acoustic Emission Characteristics of Sandstone under Freezing and Thawing

Abstract

The cyclic freezing-thawing action in cold regions leads to the deterioration of rock damage, resulting in local damage and further threatening the safety of engineering. In order to study the degradation characteristics of green sandstone and yellow sandstone under freeze-thaw cycles from macroscopic and microscopic aspects, the sandstone of a mining area in Inner Mongolia was used as experimental material. The freeze-thaw cycles were divided into 20 times, 30 times, and 40 times. NMR images and mechanical test results of two different rock samples were analyzed by binarization, NMR, and mechanical test. The test results show that, except that the mass change is less than that of yellow sandstone, the physical index degradation degree of green sandstone is higher than that of yellow sandstone, and the frost resistance is less than that of yellow sandstone. The change of acoustic emission event rate of green sandstone is mainly in the elastic deformation stage and stable crack propagation stage, and the change of acoustic emission event rate of yellow sandstone is concentrated in the crack closure stage. In the loading process, the energy release trends of the two sandstones are similar; the 30 freeze-thaw cycles are the boundary of brittle-plastic transformation of green sandstone, and the increase of cumulative energy is the most obvious. The research results provide a theoretical basis for studying the rock failure mechanism and improving the stability of rock engineering in cold regions.

Mechanical properties and acoustic emission characteristics of mixed granite after different numbers of freeze‒thaw cycles

“…9 . Through an examination of the primary frequency of rock AE, Hu 35 and Wang 31 demonstrated that the HF-LA, IF-LA and HF-LA signals correspond to the AE signals of small-scale cracks. The LF-HA signals correspond to the AE signals of medium- and large-scale fissures.…”

“…Liang et al 30 conducted AE tests on saturated sandstone after freeze‒thaw cycles and found that the higher the number of freeze‒thaw cycles, the shorter the time it takes for the rock to reach the accumulated damage threshold. Wang et al 31 studied the deterioration properties of rocks with the help of AE technology and found that the AE event rate of sandstone gradually changed from the "V" type to the "U" type. Zhou et al 32 used real-time AE technology to reveal the damage characteristics of rocks under the action of 0 and 25 freeze‒thaw cycles, applied the critical slowing theory to calculate the AE autocorrelation coefficients and variances, and explored the characteristics of the damage precursors of rocks under the action of freeze‒thaw cycles.…”