基于Casagrande法数学分析确定先期固结压力

Determining preconsolidation pressure by mathematic analysis based on casagrande method

Casagrande经验作图法是国际上通用的确定先期固结压力的方法,但其存在以下缺点:曲线绘制繁琐、若绘图比例不合适,则最小曲率半径点不易确定、人为判断误差较大。而工程中所采用的土工试验数据处理商用软件计算先期固结压力,其算法、精度分析是黑匣子,结果精度值得商榷。在总结以往研究成果基础上,结合理论研究和工程实践要求,依据《土工试验方法标准》[1],采用3次多项式和最小二乘法回归拟合压缩曲线,并考虑绘图比例影响,编写程序确定先期固结压力,最后通过具体工程土工试验数据验证了程序求解不仅能避免经验作图法的缺陷,而且结果直观清晰。

Casagrande graphing method is worldwide adopted to determine the preconsolidation pressure; but this empirical method has some drawbacks such as difficult to plot the curve and personal errors to determine the point with minimum radius of curvature when drawing scale is inappropriate. Both algorithm and accuracy analysis are unknown in these commercial software which adopted in practical projects. On the basis of previous research achievements about Casagrande method and combining theoretical study with engineering requirement, and conforming to the standard for soil test method, the paper adopts cubic polynomial and least square method to fit the compression curve; influence of drawing scale is also considered to determine the preconsolidation pressure by program. Finally, the results can not only avoid drawbacks in Casgrande method, but also exhibit results visually by the results of experimental data of practical engineering testified.