Deterioration of fresh sandstone caused by experimental freeze-thaw weathering

Abstract

Freezing and thawing are typical weathering phenomena in periglacial and permafrost areas. The fresh rock mass discovered by engineering excavation in cold climates will inevitably experience daily and seasonal cycles of freezing and thawing, significantly altering its geotechnical quality. Thus, the study of the durability of the rock mass is of great importance to engineering in cold regions. In this paper, physical and mechanical tests were carried out on sandstone samples collected from the Qinghai-Tibet Plateau after different cycles of freezing and thawing. The nuclear magnetic resonance (NMR) test was also conducted to comprehend the variation of pore structure. It was found that the physical and mechanical properties, including morphology, weight, porosity, P-wave velocity, uniaxial compressive strength (UCS) and elastic modulus, induced by freeze-thaw cycles change greatly, demonstrating an accelerated deterioration trend of sandstone. On the basis of the test results, a generalized deterioration function was presented to describe the degradation of mechanical properties. The failure modes, which reflected the fabric weakening of specimens, under axial compression after different freeze-thaw cycles were further concluded and four typical failure modes were distinguished. Finally, the deterioration mechanism of sandstone under the action of alternated freezing and thawing was discussed from the view of pore structure evolution.