The Experimental Studyon The Physical And Mechanical Properties Of Red Sandstone Under The Environment Of Freeze-thaw Environment

China is one of the biggest countries which have large area of cold regions. The area of permafrost and seasonally cold regions account approximately 3/4 of the total land area. With the increasing of cold regions construction, there have been a series of frozen rock problems. So the study of physical and mechanical properties of rock in the freeze-thaw environment is particularly important.Aiming at the engineering demands for practical problems occurred in cold regions, based on experimental research. This paper studies systematically the behaviors of mechanics and thermodynamics under conditions of freeze-thaw cycles and confining pressure. On the background of large scale rocks engineering in coupled mathematical model. The temperature field and stress field coupling of surrounding problem is numerically simulated by adopting the finite element method. Measures of prohibiting frost destruction are put forward, and the important theoretical basis is provided for the engineering construction in cold regions.The red sandstone rock was taken from the construction site, and processed into standard specimens of 50 mm in diameter and 100 mm in length. The freeze damage deterioration process freeze destruction behaviors are recorded. Analyzed the change regularity of rock mass, volume, density, P-wave velocity varying with freeze-thaw cycles and the mechanism and influence factors of rock deterioration. It is shown that four deterioration models of freeze-thaw damage, i.e. spalling model, scaling model, shedding mode and fracture mode for red sandstone were found. With the increase of freeze-thaw cycles, the rock mass, volume, density showed a trend of decrease the increase. P-wave velocity has been the trend of decrease.Then conduct mechanical properties test under different confining pressure(0MPa, 2MPa, 4MPa, 6MPa) after different number of freeze-thaw cycles(0, 5, 10, 20, 40 cycles). Analyzed the stress-strain curves of rock under different number of freeze-thaw cycles, compression strength, extreme strain, Poisson Ratio, residual strength, cohesion and inner friction angle under freeze-thaw cycles and confining pressure are analyzed. Studies have shown that compressive strength and extreme strain of red sandstone increases with the increase of confining pressure. With the increase of freeze-thaw cycles extreme stress decreases, and the corresponding compressive strength increases gradually. The rock elastic modulus, residual strength increases with the increase of confining pressure and decreases with the increase of freeze-thaw cycles. Poisson’s ratio decreases with the increase of confining pressure. With the increase of freeze-thaw cycles, cohesion, inner friction angle and frost resistance decreases with the increase of freeze-thaw cycles.Based on finite element method, the road tunnel of Daban Mountain is taken as analysis object. It is shown that with the increase of freezing and thawing time, the maximum tensile stress of the tunnel increases gradually, the maximum compressive stress decreases.At the bottom of the tunnel roof sinks gradually, tunnel upward displacement gradually increase. The thickness of the frozen ring increases gradually, but the increase speed decreases with increasing time.