冻融循环作用下土体结构演化规律及其工程性质改变机理

寒区工程被破坏的最主要原因之一就是冻融循环作用，冻融循环过程可导致土的工程性质发生较大的变化，进而导致寒区工程设施产生变形，甚至失稳。对冻融循环作用下土的结构、基本物理性质以及力学性质进行了分析和总结。研究发现：冻融循环作用后土颗粒之间的原有结构被破坏，从而形成新的结构，土中团粒会发生分裂和团聚作用，团粒粒径向均一性趋势发展，并且在不同的内部及外部条件下，土会产生不同的构造；冻融循环后，土的渗透性增大，塑性指数减小。松散土和密实土的密度以及孔隙比具有不同的变化趋势，并且可使无湿陷性的黄土状土中大孔隙增加并产生湿陷性。土的力学性质变化趋势不一，一方面这与土的构造变化直接相关，另一方面冻融循环试验方法的不同也是引起研究结果差异性较大的重要原因。因此，需要建立冻融循环作用下土工程性质变异性的判定方法、评价及预测体系，而这些也可能成为未来研究工作的方向。

Structure Evolution and Mechanism of Engineering Properties Change of Soils Under Effect of Freeze-Thaw Cycle

Freeze-thaw cycle effect is one of the most important reasons that cause engineering problems in cold zone. Freeze-thaw cycles may lead to great changes of soil engineering properties, and subsequently cause unacceptable deformation or failure of engineering facilities. The research achievements of the soil engineering change caused by freeze-thaw cycles were analyzed and summarized from structure, basic physical properties and mechanical properties of soil. After freeze-thaw cycles, initial soil fabric was destroyed and reformed, in which clayey aggregates experienced fragmentation and recombination and formed a more uniform structure. Under different internal and external conditions, soil may form different structure. After the action of freeze thaw cycle, the permeability of soil increases, plastic index decreases, porosity and density of loose and dense soils have different change trend. Soil mechanics properties show different trends in various test results. On one hand it is relate to the changes of soil structure, and on another hand different method of freeze-thaw cycle test can lead to different research results. Therefore, we need to establish the method of judgments, evaluation and prediction system for variation of soil engineering properties under the freeze thaw cycle effect, which can be become the direction of future research work.