Gibson地基模型参数的一种实用确定方法

A practical method for determining parameters of Gibson's soil model

Gibson地基在理论上可以考虑土体模量沿深度的变化,但工程应用中一直存在相关参数难以确定的问题。基于压缩试验成果和魏汝龙割线模量法双曲线模型,探讨提出确定单层和成层Gibson地基参数的实用新方法。该方法对压缩性状服从双曲线模型的土体较为适用。通过对浙江沿海地区若干典型工程的试验结果分析,结果初步表明地表处剪切模量为零的狭义Gibson地基在实际工程中几乎不存在。结合真空堆载联合预压加固软基的工程实例,对比分析了成层Gibson地基模型在沉降分析中的应用。新方法确定的成层Gibson地基模型不仅应用简便,而且可以显著地提高地基沉降预测结果的精度。在地基有效加固深度不是特别深厚的情况下,Gibson地基模型能较好地改进不能考虑模量随埋深变化的传统模型。

Although the variation of shear modulus with depth can be considered in Gibson＇s soil model,it has always been a problem for engineering practice to determine the parameters in the model.Based on both oedometer test results of soils and a hyperbolic model using the secant modulus method by Wei Rulong（1980）,a method for determining the parameters in Gibson soils is proposed for both the single-layered and the multi-layered cases.The method can be applied to soils whose stress-strain behaviors of compression obey the hyperbolic model using the secant modulus method.The results of analyzing several representative project sites in coastal regions of Zhejiang Province,China show that the special Gibson soils with a value of zero for shear modulus at ground surface keep nearly non-existent.Through the case study of a foundation treatment project using surcharge combined with the vacuum preloading technology,the multi-layered Gibson soil model with parameters calculated by means of the proposed method is thoroughly compared with other models with respect to the settlement prediction.The multi-layered Gibson soil model can give a settlement prediction with remarkably higher precision,and is also convenient in engineering applications.In the case that the effective reinforcement depth of ground is in the normal range,the Gibson soil model is recommended instead of the traditional models which ignore the variation of shear modulus of soils with depth.