Experimental study on the deterioration of red sandstone in Xumishan Grottoes under freeze-thaw cycles
Xumishan Grottoes are located in the seasonal frozen soil area of China.Long-term freeze-thaw cycles have caused serious weathering of rock mass.Therefore,the red sandstone collected from Xumishan Grottoes were prepared into three groups:natural group,60％saturated group and saturated group for freeze-thaw cycle test.The physical properties of the rock samples were recorded every 10,20,40 and 120 times to study the deterioration pattern of sandstone under freeze-thaw cycles.The results show that the mass,volume,hardness and wave velocity of rock samples show a downward trend after different freeze-thaw cycles,and the downward trend gradually becomes gentle with the increase of freeze-thaw cycles.The deterioration rate of physical properties of rock samples gradually increases after freeze-thaw cycles.The deterioration rate of physical parameters in the first 40 freeze-thaw cycles is faster,and then the deteriora-tion gradually tends to be gentle with the increase of freeze-thaw cycles.Comparing three groups of rock samples with different water contents,it is found that the deterioration rate of physical parameters of rock samples increases after the same number of freeze-thaw cycles.The cumulative damage degree of sandstone is defined based on the deterioration rates of its mass,volume,and wave velocity.A nonlinear model has been established between the cumulative damage degree and the number of freeze-thaw cycles,revealing the nonlinear growth pattern of cumulative damage degree with the increase in freeze-thaw cycles.The research findings can provide a scientific basis for the preservation of cultural relics at Xumishan Grottoes.
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