封闭系统条件下膨润土改性黏土的冻融特性研究

Study on frost heaving and thawing settlement characteristics of clayey soil modified by bentonite under closed system

为了探索膨润土改性黏土在寒冷地区作为防渗材料的可行性,以干密度、饱和度、膨润土掺量和冻融循环次数为因素,试验研究了膨润土改性黏土在封闭系统条件下的冻胀和融沉特性,分析了冻融变形变化的规律,因素影响的显著性和作用机理。结果表明:封闭系统条件下,膨润土改性黏土的冻胀融沉变形随冻融循环次数的增加而增大,二者呈双曲线关系;达到基本稳定所需的冻融循环次数较少,约为7次;冻融循环引起的冻胀率最大增量为0.49,融沉系数最大增量为0.34。饱和度的增加使土体的冻胀融沉变形增大,干密度和膨润土掺量的增加使土体的冻胀融沉变形减小;饱和度对冻胀率和融沉系数的影响显著,冻胀率和融沉系数的最大极差达1.12%和0.72%;干密度对冻胀率和融沉系数的影响显著,冻胀率和融沉系数的最大极差达0.68%和0.50%;膨润土掺量对冻融变形的影响不显著,冻胀率和融沉系数的最大极差仅0.41%和0.25%。防水、排水和隔水设计是减小膨润土改性黏土冻融变形的重要措施,膨润土改性黏土作为季节性冻土区的防渗材料是可行的。

In order to explore the possibility of clayey soil modified by bentonite as a landfill materials in cold region, the frost heaving and thawing settlement characteristics of the modified clayey soil in a closed system were studied by taking dry density, saturation, bentonite content and freeze-thaw cycle times as consideration factors.Meanwhile, the law of freeze-thaw deformation change, the significance and the action mechanism of factors were analyzed.The results showed that in a closed system, the frost heaving and thawing settlement deformation of the modified clayey soil increased with the increasing freeze-thaw cycles, which was a hyperbolic relationship and stabilized after about 7 freeze-thaw cycles.The maximum increase of frost heaving ratio and thawing settlement coefficient caused by freeze-thaw cycles was 0.49 and 0.34 respectively.The increase of saturation could boost deformation of frost heaving and thawing settlement, the increase of while dry density and bentonite content had a reverse effect.Saturation had a significant impact on frost heaving ratio and thawing settlement coefficient, and the maximum range of frost heaving ratio and thawing settlement coefficient was 1.12 % and 0.72 %.The effect of dry density on frost heaving ratio and thawing settlement coefficient was generally significant, the maximum range of frost heaving ratio and thaw settlement coefficient was 0.68 % and 0.50 %.The effect of bentonite content on freeze-thaw deformation was not significant, and the maximum range of frost heave ratio and thaw settlement coefficient was only 0.41 % and 0.25 %.Waterproof, drainage and water separation design are important measures to reduce the freeze-thaw deformation of bentonite modified clayey soil, which is feasible as the landfill materials in seasonal frozen soil region.