饱和度对泥质粉砂岩冻结力学性质的影响

饱和度对泥质粉砂岩常温下力学性质的影响已多有讨论，但对其冻结状态下力学性质的影响尚不明确。对6种饱和度（0%、20%、40%、60%、80%、100%）的泥质粉砂岩样品冻结前后的纵波波速、核磁共振T₂谱、冻结状态下的抗拉强度和点荷载强度进行了测试，试验结果表明：（1）冻结状态下，随饱和度的增加，纵波波速呈现先降低后升高的趋势；（2）在-20℃下，完全饱和样品内部孔隙水有49.2%保持未冻，60%饱和度的样品有81.4%未冻，而20%饱和度样品有87.4%的孔隙水没有冻结；（3）冻结状态下岩样的抗拉强度和点荷载强度随初始饱和度的增加均呈现减小-增加-减小的趋势，在饱和度80%左右均有一极大值，且两个强度的最大值均不出现在饱和度100%时。分析后发现，在低饱和度的状态下，冻结岩石的强度仍取决于孔隙中的未冻水含量；而在高饱和度的区间，孔隙冰的含量决定了其冻结强度；对于接近饱和的岩石，其冻结强度还受到冻胀损伤的影响。

Influence of saturation degree on the mechanical properties of frozen argillaceous siltstone

Influence of saturation degree on the mechanical properties of argillaceous siltstone at room temperature has been widely investigated, but at subzero temperature there is still unclear. In this paper, the P-wave velocities and the NMR T₂ spectra of argillaceous siltstone samples with 6 different saturation degrees (0%, 20%, 40%, 60%, 80%, 100%) before and after freezing have been studied, as well as the tensile strength and the point load strength of these samples in frozen state. The results indicated that:(1) the P-wave velocities of frozen samples rise first and then fall with the increase of their saturation degrees; (2) 49.2% of the pore water in the totally saturated sample remain unfrozen at -20℃, while this value is 81.4% and 87.4% for 60% saturated sample and 20% saturated sample, respectively; (3) the frozen tensile strength and point load strength of samples both show a drop-rise-drop trend following the increase of saturation degrees, for both strengths the maximum value appears at saturation degree of 80% and the peak value does not emerge at saturation degree of 100% unexpectedly. The following conclusions can be drawn:in low-saturation degree interval, the strength of frozen rock is primarily determined by the content of unfrozen porous water; while in high-saturation degree interval, the content of porous ice controls the frozen strength; for rock close to full saturation, frost damage is also a key influence for the frozen strength.