青藏粉土单向冻结冻胀率变化特性研究

Experimental study of the development characteristic of frost heaving ratio of the saturated Tibetan silt under one-dimensional freezing

开展了饱和青藏粉土在开放系统不同温度梯度条件下的单向冻结试验,对冻结过程中冻结深度和冻胀速率的发展变化过程进行了研究.结果表明:不同顶板温度下,土样均在25 h左右达到冻结稳定状态,之后冻结深度基本不再发生变化.土样冻结过程中,冻胀速率表现为快速减小、较小值保持稳定、快速增大、较大值保持稳定四个阶段.基于以上试验结果,对土样冻结过程中冻胀率的变化过程进行了研究,发现冻胀率随冻结深度的增加先减小后增加,冻胀率从减小变为增大的时刻就是冻结深度趋于稳定的时刻,而冻胀率快速增大的时刻为冻胀速率进入较大值保持阶段的时刻.冻胀率变化的内在机理为土样冻结过程中由冰透镜体分凝所导致的未冻区固结和已冻区冻胀共同作用的结果.

Based on one-dimensional freezing test under five different cooling temperature gradients in an open system,the frozen depth and frost heaving ratio of the saturated Tibetan silt are studied experimentally. Some conclusions are showed as following. Firstly,although the top cooling temperatures are different,but the freez-ing front in sample reaches stability near 25 hours. In the freezing process,the frost heaving rate undergoes four stages,which are rapid decrease stage,stable stage,rapid increase stage and another stable stage. The frost heav-ing ratio is related to the development of the frozen depth and the frost heaving rate. The frost heaving ratio be-come to increase when the frozen depth tends to stable. The last stable stage of frost heaving rate contributes mostly to the increasing of frost heaving ratio. The mechanics of the development of the frost heaving ratio is in-duced by the combined effect of the unfrozen part consolidation and frozen part frost heave of soil sample.