基于Harris函数的2级加载固结试验方法及可靠性判别准则

Two-level-loading consolidation test based on Harris function and it's reliability criterion

为提高获取土体压缩模量和先期固结压力的土工试验测试效率,在采用Harris函数描述土体e-lgp曲线的基础上,提出2级加载确定土体压缩特性的固结试验方法,其在确定压缩模量Es和先期固结压力pc时的适用性得到了京沪高铁和京津城际铁路地基土样的验证。研究结果表明:由土体初始孔隙比e_0和2级加载稳定变形值可以准确计算压缩曲线的Harris函数表达式,除小于100 kPa时外,其余压力段压缩模量Es误差基本小于10%,平均误差仅为5.59%;利用Harris函数可得到压缩曲线最小曲率半径点坐标和直线段斜率解析值,所得先期固结压力的Casagrande法计算值与土体埋深呈明显正相关,且与上覆压力的比较结果和试验段实测分层沉降发展规律吻合;以压缩指数Cc为评价指标,通过概率模型建立固结试验可靠性判别准则,研究成果为简化固结试验方法,快速确定土体压缩参数提供了新途径。

This paper aims at improving the geotechnical test efficiency for obtaining modulus of compression and preconsolidation pressure. By utilizing the Harris function to depict the e-lgp curve, a consolidation test method of two-level-loading was proposed for measuring the compressibility of undisturbed soil. The applicability of this method on calculating modulus of compression Es and preconsolidation pressure pc was verified by the samples from Beijing-Shanghai high speed railway and Beijing-Tianjin intercity railway. The conclusions are made as follows： A compression curve expressed by the Harris function can be acquired through the soil initial void ratio e0 and the deformation values under two-levels load, and the error of compression modulus is mainly less than 10% except when the pressure section is less than 100 kPa. Moreover, the average error stays only 5.59%. The coordinate point of minimum curvature radius and the slope of straight line can be found accurately by using Harris function. There is a positive correlation between the preconsolidation pressure obtained by Casagrande method and soil depth, and the comparison with burden pressure fits settlement law of test sections well. By selecting compression index as evaluation indicator, the reliability criterion of consolidation test was established according to probability model. The research results provide new approach for simplifying consolidation test method and ascertaining soil compressible parameters rapidly.