分散性土及工程应用的研究进展

Advances in Research and Engineering Applicaitons of Dispersive Soil

分散性土在世界各地特别是干旱半干旱地区分布广泛,属于一种水敏性的特殊土,抗水蚀能力很低,容易形成管涌、洞穴、冲沟等破坏,对建筑物的安全性造成严重威胁。对分散性土的定义与内涵、分散机理、鉴定方法、改性应用进行了分析、总结与展望。分散性土是一种在水力坡降很低条件下由于土颗粒间的排斥力超过吸引力而导致土体产生分散流失的黏性土。分散性土的形成机理在于土体中的胶结物质特别是黏粒含量低或土体中含有较多的钠离子和酸碱度呈碱性。一般采用双比重计、碎块、针孔、孔隙水可溶性阳离子和交换钠离子百分比等室内试验结果来综合鉴定土样的分散性,野外调查和经验模型等方法可作为辅助鉴定手段。采用物理保护、化学改性或综合处治提高分散性土的水稳性,其中化学改性是最根本的方法。在未来的研究中,应重视与加强研究土粒间斥力与引力关系、探索分散性土渗透破坏特别是土体裂缝演变规律、研发经济高效环保的改性材料等方面工作。

Dispersive soil is widely distributed all over the world, especially in arid and semi-arid areas. It is a kind of special soil with water sensitivity. Its water erosion resistance is very low. It is easy to cause piping, caves, gullies and other damages, which poses a serious threat to the safety of buildings. In this paper, the definition, dispersive mechanism, identification methods and modification application of dispersive soil were analyzed, summarized and prospected. Dispersive soil is a kind of cohesive soil prone to loss, which soil particles will disperse under very low hydraulic gradient when the repulsion force between soil particles exceeds the attraction force in low salinity or pure water. The formation mechanism of dispersive soil is that the content of cementing substance in soil, especially clay particles is low or the soil contains more sodium ions and is alkaline. In general, laboratory tests such as double hydrometer test, crumb test, pinhole test, soluble cations in pore water test and exchangeable sodium percent test are used to synthetically judge the dispersion of soil samples. Field investigation and empirical model can be used as auxiliary means. In dispersive soil engineering applications, the water stability of dispersive soil can be improved by physical protection, chemical modification or comprehensive treatment, among which chemical modification is the most fundamental method. In future researches, the relationship between repulsion and attraction of soil particles, the seepage damage of dispersive soil, especially the evolution law of soil cracks, and cost-effective, efficient and clean modified materials should been payed more attention.