条形基础下砂黏土双层地基极限承载力预测模型的不确定性分析

实际工程中常见砂—黏土双层地基,在这种分层地基的极限承载力问题上传统的太沙基承载力公式不再适用.工程中常用的条形基础下,砂—黏土双层地基极限承载力半经验计算方法可能会提供不可靠的预测.文中采用一种基于极限分析上限解的方法——不连续布局优化(DLO)对砂—黏土双层地基的极限承载力进行了计算.在传统地基承载力公式的基础上引入了承载力折减系数,给出了不同工况下该系数的设计图表.基于DLO的计算结果,提出了一个可适用于取值范围广泛的几何和土体强度参数的多项式回归公式.基于文献中条形基础下,砂—黏土双层地基极限承载力计算结果对所提出的简化公式进行了验证和不确定性分析.

Analysis of the model uncertainty for predicting the ultimate bearing capacity of strip footings on sand overlying clay

A sand layer overlying clay is common in practice. The conventional Terzaghi''s bearing capacity theory is unavailable in this type of nonhomogeneous soil. The semi-empirical methods toward addressing the bearing capacity of strip footings on sand overlying clay, which are widely used in geotechnical engineering, may yield unreliable solutions. In this paper, the bearing capacity of footings on sand overlying clay is evaluated using discontinuity layout optimization (DLO), which is a rigorously upper bound limit analysis method. A bearing capacity reduction factor is developed based on the conventional Terzaghi''s bearing capacity theory, and a set of design charts of this factor for various scenarios is illustrated. Subsequently, a simplified regression-based approach, relevant to a wide range of geometric and strength parameters, is proposed. Based on a database of the bearing capacity of footings on sand overlying clay from prior literatures, the model uncertainty for the proposed method is validated and characterized.