饱和土冻结透镜体生长过程水热耦合分析  

Ice lens growth process involving coupled moisture and heat transfer during freezing of saturated soil

作　　者：周扬[1,2] 周国庆[1,2] 周金生[1,2] 王建州[1,2] 

机构地区：[1]中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221008 [2]中国矿业大学建筑工程学院,江苏徐州221008

出　　处：《岩土工程学报》2010年第4期578-585,共8页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金重点项目(50534040);国家自然科学基金项目(40471021);国家科技计划重点项目(2006BAB16B01)

摘　　要：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。A model is developed to describe one-dimensional growth process of ice lens during freezing of saturated soil.Main factors controlling thickness and movement of unfrozen liquid film in frozen soil are analyzed by use of the thermodynamic theory for the liquid layer near a substratum.Water movement in the active zone is dealt with as Darcy flows controlled by a new concept called equivalent pressure,and a new model of coupled moisture and heat transfer is constructed based on it.The mechanism of ice lens growth process is studied,and the concurrence of uplifting effect caused by disjoining pressure and suction effect controlled by equivalent pressure during coupled process in active zone is indicated.The existence of frozen fringe is regarded as the indispensable condition for active lens growth in non-highly-colloidal soil with no pressure in supply water.Tests on continuous freezing and intermittent freezing are conducted for frost susceptive soil,and experimental results of final ice lens growth in both tests are used to testify the model and computation.The study shows that the calculated results are in agreement with the observation;and for the intermittent freezing,the disappearance of frozen fringe during the intermittent stage prevents the growth of final lens,thus the frost heave is partially controlled because of the deficient growth of final lens.Finally,problems about optimizing cold end temperature in order to control the frost heave are discussed.

关 键 词：冻结技术 冻胀 冰透镜体 水热耦合 间歇冻结 冻胀控制 

分 类 号：TU445[建筑科学—岩土工程]