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针对饱和土一维冻结过程中出现的冰透镜体,从水热耦合的角度建立了描述其生长过程的模型。利用固体表面水膜的热力学理论分析了冻土中未冻水膜厚度及其流动的控制因素,引入等效压力的概念,指出主动区内的水流可以看作等效压力控制下的达西流,并以此为基础建立了主动区内的新水热耦合模型;透镜体的生长表现为主动区水热耦合过程中透镜体底端在分离压力作用下的抬升及负等效压力作用下的吸水,对这两种作用的分析表明,冻结缘的存在是非高胶质性土壤在无压补水条件下活动透镜体生长的必要前提。分别进行了冻胀敏感性土的连续冻结及控制冻深的间歇冻结试验,以两组试验中末透镜体的生长过程验证了模型及计算的正确性。结果表明:模型很好的反应了两组试验中末透镜体的生长过程;间歇冻结模式在间歇阶段锋面退化,冻结缘消失导致末透镜体生长停止,其生长曲线呈台阶型,冻胀由于末透镜体发育较差而受到一定抑制。最后对冻结模式的优化设计以控制冻胀的技术问题进行了进一步的探讨。
In view of the ice lens body appearing in the one-dimensional freezing process of saturated soil, a model describing its growth process is established from the perspective of hydrothermal coupling. Based on the thermodynamics theory of solid surface water film, the thickness of unfrozen water film in frozen soil and its controlling factors are analyzed. The concept of equivalent pressure is introduced. It is pointed out that the water flow in active area can be regarded as Darcy flow under equivalent pressure control , And based on this, a new hydrothermal coupling model was established in the active zone. The growth of the lens body was manifested by the uplift of the bottom of the lens body under the action of separation pressure and the negative equivalent pressure during the hydrothermal coupling of the active zone Water absorption. The analysis of these two effects shows that the existence of frozen edge is a necessary prerequisite for the growth of non-gummy soil under the condition of non-pressure water supply. The frozen freezing-sweeping soil and the freezing-freezing intermittent freezing test were carried out separately. The correctness of the model and the calculation were verified by the growth of the lens-free body in the two experiments. The results show that the model well reflects the growth of the lens system in both groups. The intermittent freezing mode degenerates in the intermittent phase, and the disappearance of the frozen edge leads to the termination of the growth of the lens. The growth curve of the lens system is stepwise. Lens development is poor and subject to certain inhibition. Finally, the technical problems of frost heave control in the optimized design of freezing mode are further discussed.