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冻融循环对土的结构以及物理力学性质有着重要影响,其变化与冻融过程中的孔隙水压力变化有密切关系。但土体冻结过程中的孔隙水压力测试一直是冻土土工测试试验的技术难题。针对这一难题,研发了一种适用于冻结土体孔隙水压力测试的探头,并对砂土和粉质黏土在冻融循环过程中的孔隙水压力发展变化进行了实时监测,获得了圆柱试样冻融循环过程中不同深度处的孔隙水压力变化过程。在冻结过程中,粉质黏土形成冻结缘区及可视的分凝冰,而砂土则无冻结缘及分凝冰的形成。冻融循环过程中土体内部的孔隙水压力变化受温度、冻结速率、冻融循环以及土质等因素的影响。孔隙水压力随温度的循环变化而经历周期性变化:冻结过程中,孔隙水压力不断下降,吸力不断增加;融化过程中,孔隙水压力增大。而冻结速率、冻融循环及土质主要对孔隙水压力降的幅值变化产生影响。此外,冻结锋面位置附近孔隙水压力的下降、吸力的增加,正是水分由未冻区向冻结区迁移的主要驱动力。根据以上试验结果及其理论分析发现,所研制的孔隙水压力探头具有一定的实用性。
The freeze-thaw cycle has an important influence on the structure and physico-mechanical properties of soil, and its change is closely related to the change of pore-water pressure during the freeze-thaw cycle. However, the test of pore water pressure in frozen soil has always been a technical problem in the geotechnical test of frozen soil. In response to this challenge, a probe suitable for the pore water pressure test of frozen soil was developed. The development of pore water pressure during the freeze-thaw cycle of sand and silty clay was monitored in real time. Cylindrical test Changes of pore water pressure at different depths during the freeze-thaw cycles. During the freezing process, the silty clay forms the frozen margin and the visible condensate ice, while the sand does not have the frozen edge and the formation of freezing ice. The pore water pressure inside the soil during the freeze-thaw cycles is affected by factors such as temperature, freezing rate, freeze-thaw cycles and soil quality. Pore water pressure undergoes cyclical changes with the cyclic changes in temperature. During the freezing process, the pore water pressure continuously decreases and the suction force increases continuously. During the melting process, the pore water pressure increases. The freezing rate, freeze-thaw cycle and soil quality have an impact on the amplitude change of pore water pressure drop. In addition, the reduction of pore water pressure near the front of the frost and the increase of the suction force are the main driving forces for the migration of water from the unfrozen area to the frozen area. According to the above test results and theoretical analysis, it is found that the developed pore water pressure probe has some practicality.