冻融循环作用下层理砂岩物理特性及劣化模型

Physical characteristics and degradation model of stratified sandstone under freeze-thaw cycling

岩石在冻融环境下发生的损伤与其层理结构密切相关,同时冻融损伤作为一种综合表现,单纯考虑岩体内部某一种尺度缺陷或外部单一因素在冻融循环作用下的变化,不足以客观反映损伤情况。对垂直、平行层理试样开展0、20、40次冻融试验,首先探究了层理砂岩在冻融过程中的损伤发育特征,之后基于Ф100 mm SHPB试验装置,进行5种弹速下的冲击试验,分析了冻融循环条件下层理砂岩冲击破碎块度分布规律,以冻融损伤累积与破碎块度的相关性为理论依据,以力学性质的冻融劣化为思想建立了层理砂岩的冻融劣化模型,研究结果表明:冻融环境下,两种试样孔隙发育、纵波波速表现出显著差异,平行层理试样相对更容易发生损伤;各级冲击弹速下破碎块度分布与冻融循环次数之间存在正相关、负相关以及波动型3种相关关系;劣化模型基于负相关区域数据和成比例相同区域数据得到的强度、峰值应变计算值与实测值非常接近,基于正相关区域数据得到的强度计算值也与实测值有很好的一致性。

The damage of rock caused by freezing and thawing is closely related to its bedding structure, and the freeze-thaw damage is a comprehensive performance. A simple consideration of the change of a single defect inside rock mass or a single external factor under freezing and thawing cycles is insufficient to objectively reflect the damage. In this paper, freeze-thaw tests subjected to 0, 20, 40 freeze-thaw cycles were carried out on the vertical and parallel layered samples. The damage development characteristics of the layered sandstone during the freezing and thawing process were explored. Based on the Ф100 mm SHPB test device, impact tests at five types of speed were carried out, and the distribution law of impact crushed degrees of layered sandstone under the condition of freeze-thaw cycles was analysed. Based on the correlation between the accumulation of freeze-thaw damage and the degree of crushing, a freeze-thaw degradation model of layered sandstone was established by the deterioration of mechanical properties. It is found that under the action of freezing and thawing, the longitudinal wave velocity, pore development and impact crushing morphology of these two types of layered sandstone samples are significantly different. There are three correlations between the degree of fragmentation and the number of freeze-thaw cycles, i.e. positive correlation, negative correlation and fluctuation. The calculated values of the intensity and peak strain obtained from the negative correlation region data, as well as the proportional and overlapping area data, are very close to the measured values. The calculated values of the intensity based on the positive correlation data are also in good agreement with the measured values.