Abstract: In order to study the effect of freeze-thaw on the mechanical properties of rock with different grain sizes,three
kinds of quartz sands with grain sizes ranging from 0. 125 to 0. 25 mm,0. 3 to 0. 5 mm,and 0. 6 to 1 mm were selected as the
aggregates to make quasi-sandstone specimens. Freeze-thaw cycles and uniaxial compression acoustic emission (AE) tests were
conducted to analyze the effects of freezing and thawing on the mechanical and acoustic emission properties of sandstones with
different grain sizes. The results show that:① With the increase of the number of freeze-thaw cycles,the porosity of the specimen
gradually increased,the proportion of small pores decreased,the proportion of large and medium pores increased,the modulus
of elasticity and uniaxial compressive strength showed a decreasing trend,and the magnitude of the change was positively
correlated with the particle size;② The AE count counts can be divided into a calm phase,a slow-growth phase and a suddengrowth
phase. As the number of freeze-thaw cycles increases,the accumulate AE counts show a trend of increasing and then decreasing,
and the coarse-grained specimens are the first to reach the maximum value;③ The AE b-value evolution of sandstones
of different grain size classes can be divided into a fluctuating upward stage,a drastic downward stage,and a smooth
stage. The AE b-value evolution shows three distinct phases:fluctuating increase,dramatic decrease,and plateau. The AE b-values
of coarse,medium and fine-grained specimens decreased to 0. 8,1. 25 and 1. 65 in the steady phase,respectively,and this
phenomenon can be used as a precursor warning for the destabilization damage of freeze-thawed sandstones with corresponding
grain sizes.