基于分散机理的细粒土分散性判别方法研究

Discrimination methods for dispersivity of fine-grained soils based on dispersive mechanisms

针孔、碎块、双密度计、孔隙水可溶性阳离子和交换性钠离子百分比等现有评价细粒土分散性的5种常规试验方法,操作过程繁琐,耗时耗力。基于细粒土分散机理,通过人工配制不同黏粒含量、不同碳酸钠质量分数的土样,研究细粒土分散性常规判别试验方法的适用性,提出快速准确评价细粒土分散性的方法。试验结果表明,分散土可分为物理性分散土(可称之为低凝聚性土)、化学性分散土、物理-化学复合型分散土,其中黏粒含量10%是细粒土产生物理性分散的界限。泥球、孔隙水可溶性阳离子和交换性钠离子百分比试验适用于所有细粒土,针孔和双密度计试验适用于黏粒含量不低于10%的细粒土。当黏粒含量低于10%时,采用泥球试验的判别结果作为判别依据;当黏粒含量不低于10%时,以泥球和针孔试验的判别结果作为综合判别依据,并且以最强的分散性判别结果为准。双密度计、孔隙水可溶性阳离子、交换性钠离子百分比和酸碱度试验仅作为细粒土分散机理的解释性试验,不参与综合判别。

The crumb tests, the pinhole tests, the double-hydrometer tests, the pore water soluble cation tests and the exchangeable sodium ion percentage tests are the common methods for identifying the dispersivity of the fine-grained soils,which are complex and time-consuming. Based on the dispersive mechanisms of the fine-grained soils, the soil samples with different clay contents and sodium carbonate mass fractions are prepared artificially to analyze the suitability of the conventional discrimination methods for dispersivity and to propose a rapid and accurate discrimination method. The results show that the dispersive soils can be divided into physical dispersive soils which can be called low cohesive soils, chemical dispersive soils and physical-chemical composite dispersive soils. It also can be found that 10% of the clay content is the upper limit of physical dispersivity of the fine-grained soils. The mud ball tests, the pore water soluble cation tests and the exchangeable sodium ion percentage tests can be applied to all fine-grained soils, and the pinhole tests and the double-hydrometer tests are suitable for the fine-grained soils with a clay content no lower than 10%. The results of the mud ball tests should be used as the discrimination criterion for dispersivity if the clay content is lower than 10%, otherwise the discrimination criterion for dispersivity should be the strongest dispersivity results of the mud ball tests and the pinhole tests.The double-hydrometer tests, the pore water soluble cation tests, the exchangeable sodium ion percentage tests, and the pH tests are used as the explanatory tests for the dispersive mechanisms of the fine-grained soils, which have no influences on the comprehensive discrimination.