冻融与静荷载双重作用下土体内部孔隙水压力、水分场变化规律研究

Research on Changing Laws of Pore Water Pressure and Moisture Field in Soil Subjected to the Combination of Freeze-thaw and Static Load Actions

在季节冻土区,土体内部孔隙水压力和水分含量受冻融循环和外部荷载的影响.通过模型试验,利用孔隙水压力传感器和水分传感器对冻融与静荷载双重作用下黄土内部的孔隙水压力和水分含量进行监测,得到不同深度处孔隙水压力和水分含量的变化过程.结合静荷载的应力场,进一步分析孔隙水压力和水分含量的空间变化规律.试验结果表明:在冻融与静荷载双重作用的初期,土体内部孔隙水压力快速增大;之后,孔隙水压力开始随温度呈周期性变化.在一个冻融周期内,土体内部孔隙水压力和水分含量都随温度的升高而增大,随温度的降低而减小,而且孔隙水压力和水分都随温度的变化而表现出滞后性.随着冻融循环次数的增加,孔隙水压力在荷载下方和两侧形成三个集中区;水分则在荷载下方形成高含水量区,在荷载两侧形成低含水量区.通过对静荷载产生的应力场进行分析发现,土体内部孔隙水压力和水分场的空间分布与静荷载产生的应力场有密切关系.

In the seasonal frozen regions, the pore water pressures and water contents in soil are influenced by freeze-thaw cycles and external loads. In the model test, the sensors of pore water pressure and water content were used to measure the variations of pore water pressures and water contents of the loess under the freeze-thaw cycles and static load, and the changing process of pore water pressures and water contents at different depths of soil was obtained. The relationship between static stress and pore water pressures in the space was then examined. It is found that the pore water pressures of soil increased rapidly at the beginning of freeze-thaw and static load actions; and the pore water pressure then changed periodically with the temperature. In a freeze-thaw cycle, soil pore water pressure and moisture content increased with the increase of temperature, and decreased with the decrease of temperature. In addition, the pore- water pressure and moisture had hysteretic quality with the changing of temperature. Moreover, three concentrated areas of pore water pressure from the longitudinal section with the increasing number of freeze-thaw cycles were observed, one was directly below the loading position, and the other two were located between the edge of loading area and test chamber. Meanwhile, a high water content area below the static load and low water content areas on both sides of the static load were also found. Under the static load, the distribution of pore water pressure resembled the stress field calculated by the corner-points method. It is also considered that the present of these concentrated areas was related to the stress field of soils produced by the static load.