软黏土上覆砂层的条形基础承载力分析

Computation of bearing capacity of strip footing on sand overlying soft clay soil

【目的】对软黏土上覆砂层的条形基础承载力进行分析,为土层存在软弱下卧层情况下的浅基础设计提供理论参考。【方法】采用理论推导的方法,在扩散投影模型的基础上,根据基础下方砂土层微元体的受力分析,推导出砂层下卧黏土层时条形基础的极限承载力计算公式,并给出了参数取值建议。【结果】根据分析,基础宽度、砂土层厚度、砂土层强度、黏土层强度、荷载扩散角等因素都对浅基础的极限承载力有一定影响,在建立的模型中对这些因素均进行考虑。为验证该模型的有效性,对已有的离心机试验模型进行了计算,得出用推导的公式计算出的极限承载力与离心机试验数据十分接近,模型相对误差均小于10%。【结论】该公式可用于软黏土上覆砂层时的条形基础承载力计算。

[Objective] The analysis of the bearing capacity of a strip foundation under the circumstance of sand overlying soft clay can provide a reference to the design of shallow footing where weak subsoil exists. [ Method ] A theoretical derivation method is applied on the basis of the spread projection model, and the computation formula of strip footing bearing capacity on sand overlying clay soil is derived according to the stress analysis of the sand element beneath the footing. [ Result] For the convenience of calculation, the determined parameters in the formula are given. According to the analysis, factors such as footing width, the thickness of the sand layer, the shear strength of sand and clay and the spread angle of the load have an influence on the bearing capacity, and they are considered in the formula. To prove the effectiveness of the formula, the bearing capacities of centrifuge models in the classic articles are calculated by the derived formula. [ Conclusion]The comparison shows that the relative errors between the formula and centrifuge experimental tests are less than 10%, indicating that the formula can be applied in computing the bearing capacity of strip footing on sand overlying soft clay.