界限含水率试验——液塑限联合测定法两点法研究

Two-Point Method of Liquid and Plastic Limit Water Content Joint Measurement

液塑限联合测定法的试验原理是在双对数坐标上,锥入深度与含水率呈线性关系。为确保结果准确或判断异常,规范要求分取三份不同含水率的均匀试样测锥入深度,计算液限、塑限和其它塑性指数。根据液塑限试验经验,大部分土类直线性非常好。对两点法进一步研究发现了两点最佳取值范围。采用重复试验法比较三点法与两点法的优劣,发现两点法结果精密度更高,超差率更低,更容易满足规范质量要求。用理论推导得到两点取值范围,用试验验证理论推导。

The principle of liquid and plastic limits water content joint measurement method is that the depth measured by a cone penetration of a cohesive soil is linear with its water content in the double logarithmic coordinate system.In order to en-sure the accuracy of these results or to judge abnormalities,it is needed to measure three different depths of one uniform cohe-sive soil samples in different water contents to calculate the liquid limit water content and the plastic limit water content.The author's years'experience in the liquid and the plastic limits analysis has shown that most types of soil have excellent linearity.Based on the mathematical theorem that two points determine the line,any two points can obtain the line.Further study of the two-point method,the ideal depth range was found.It is shown that the two-point method can ensure the quality better and the lower out-of-tolerance rate by the repeated test to three-point method.In this paper,ideal depth range of the two-point method is obtained by the theoretical deduction and is verified by experiments.