竖向渗透分层取样技术在液塑限联合测定试验中的应用

Application of Vertical Penetration Stratified Sampling Technique in Liquid-Plastic Limit Combined Testing

岩土工程实践中,一般通过测定黏性土的液塑性指数来确定其具体分类,并据此判断土体的基本工程性质。但目前《土工试验方法标准》(GB/T 50123—2019)中推荐的液塑限联合测定试验法存在一定的缺陷,制作出的土样干密度差异明显,使得试验过程中得到的数据点在双对数坐标轴上离散性很大。通过对国标中推荐的液塑限联合测定法进行改进,得到了一种新的联合测定法——竖向渗透分层取样液塑限联合测定法,这种测定法在制作土样时流程更为严密,使得数据在双对数坐标轴上呈现出很好的线性关系。对网纹红土、棕钙土、淤泥质土和潮土4种土样的界限含水率进行室内测试,验证了所制备试样干密度均匀、含水率分布层次丰富;将实施改进的试验方法与国标推荐法进行对比分析,并结合十字板剪切试验结果,进一步验证了改进方法的合理性。

In geotechnical engineering practice,the specific classification of a clay soil is generally determined by measuring its liquidity and plasticity index,and the basic engineering properties of the soil are determined accordingly.However,the liquid-plasticity limit(LPL)method recommended in the Standard for Geotechnical Test Methods(GB/T 50123—2019)has some shortcomings as the soil samples produced by the method differ significantly in dry density,which makes the data points obtained during the test discrete in the double logarithmic coordinate axis.In this paper,a new test method,the vertical penetration stratified sampling liquid-plastic limit joint test method,is developed by improving the liquid-plastic limit joint test method recommended in the national standard.The proposed method is more rigorous in the preparation of soil samples and shows a good linear relationship on the double logarithmic axis.The boundary moisture content of four soil samples,namely,reticulated red soil,brown caliche,silt loam and tidal soil,is tested in house to verify the uniformity of dry density and the richness of moisture content distribution levels of the prepared samples.Comparison between the proposed method and standard-recommended method as well as plate shear test result further verify the rationality of the present method.