膨胀土的自由膨胀比试验研究

自由膨胀率是膨胀土判别与分类的一项重要指标,由于自由膨胀率的测试人为干扰因素较多,自由膨胀率的科学性和可靠性被广泛质疑,因此,寻求一种人为干扰因素少,又能反映膨胀土本质的合理而适用的指标具有重要意义。为此,引进了一种新的试验方法即自由膨胀比试验,膨胀比是10g烘干土样分别在盛有蒸馏水和煤油(或CCl4)的标准量筒(通常为50mL)中沉积稳定时的体积之比。阐述该指标的意义和试验方法,系统开展自由膨胀比试验和膨胀土物理力学指标试验,试验表明:相对自由膨胀率而言,自由膨胀比与阳离子交换量、比表面积、蒙脱石含量具有更好的相关性,能较好反映膨胀土的胀缩特性;将自由膨胀比与公路规范中常用的指标液限、塑性指数、标准吸湿含水量进行对比分析,发现自由膨胀比作为膨胀土判别与分类指标具有更高的可信度,同时自由膨胀比与这些指标相关关系也较好,可将其结合起来用于膨胀土的判别分类中。

TESTING STUDY ON RELATIVE FREE SWELLING RATIO FOR EXPANSIVE SOIL

Free swelling ratio is an important index for identification and classification of expansive soil.In the process of its tests many artificial factors exist,and its scientific and reliability are widely doubted,so searching an adequate and applicable index with fewer artificial factors and representing the nature of expansive soil is of significance.A new kind of testing measure is introduced.That is relative free swelling ratio test.The relative free swelling ratio is defined as the ratio of the equilibrium sediment volume of 10 g oven-dried soil in distilled water to that in coal soil(or CCl4).The significance of the index and the testing measure are described.Relative free swelling ratio and physical and mechanical properties tests for expansive soil are conducted systematically.From the tests it is found out that when compared to free swelling ratio,relative free swelling ratio shows better correlation with cation exchange capacity,specific surface and montmorillonite content,so it is concluded that relative free swelling ratio is consistent with the index which exhibits the nature of expansive soil.The credence is compared with the indices suggested by specifications for highways including liquid limit,plastic index and standard moisture absorption water content and the results indicate that the former shows a higher credence and possesses more feasibility,meanwhile the correlations between the relative free swelling ratio and other indices are good,so these indices should be considered together for identification and classification of expansive soil.