Research on Physical and Mechanics Properties of Metamorphic Sandstone Subjected to Freeze-thaw Cycles

Abstract

The Sichuan-Tibet Railway passed through high-altitude metamorphic rock areas in western Sichuan, where rock freeze-thaw weathered intensely and geological disasters occured frequently, it was of great theoretical significance and engineering value to carry out freeze-thaw cycle tests on typical rocks. The metamorphic sandstone samples collected from the Lancang River Basin were divided into five groups, each group experienced freezing and thawing about 8h(4 h freezing and 4 h thawing) of wide temperature range whose freezing temperature was -40 °C and thawing temperature was 50 °. During the experiment, loss of quality, change in P-wave velocity of metamorphic sandstone were counted with observing deterioration in the appearance of rock specimens every certain number of cycles, combining with uniaxial compression tests after 22, 42, 65, 85, and 105 times of freeze-thaw cycles respectively. Comparing and analyzing the calculated physical and mechanical parameters, the result shows that with increasing cycles of freezing and thawing, the quality first drops, then reaches a minimum after 40∼50 cycles, and oscillates and stabilizes finally. The P-wave velocity of the sample is large after freezing, and is numerically higher than the P-wave velocity after thawing. Overall, the P-wave velocity and quality change trend have good consistency. The uniaxial compressive strength of specimens has no obvious regular pattern. The structural plane has an important influence on the freeze-thaw cycle test results, the research on the mechanism of structural freeze-thaw degradation is an important part of revealing the stability of rock mass in alpine region.