基于综合变异系数的地基承载力可靠性分析

采用一次二阶矩法，考虑岩土参量变异系数的试验及历史数据，提出了基于综合变异系数的地基承载力简化可靠性与风险分析方法。利用提出的简化可靠性与风险分析方法，可在传统确定性分析的基础上，采用合理的变异系数，分别得到与地基承载力有关的可靠度、破坏概率和平均期望损失的最可能值及其变化范围，为提出优化的地基基础设计方案和工程决策奠定基础；相对于土重度和黏聚力，地基承载力可靠度对于内摩擦角的变化更加敏感；设计时可以综合考虑所需的安全系数、可靠度和破坏概率，确定合适的基础宽度或基底面积。当地基土的场地勘察统计结果的变异系数权重逐渐增加时，综合变异系数不断减小，其相应的地基承载力的可靠度逐渐增加，而相应的破坏概率逐渐减少。

Reliability analysis of foundation bearing capacity based on combined coefficients of variation

A simplified reliability and risk analysis method of foundation bearing capacity based on combined coefficients of variation of random variables is proposed using first order second moment technique. The laboratory results and historical published ones of coefficients of variation are taken into consideration as the combined coefficients of variation, which are adopted as the calculated coefficients of variation. The most likely values and their possible ranges of degrees of reliability, probabilities of failure and average expected losses can be obtained using suitable coefficients of variation besides the conventional deterministic analysis. This enables to make optimal design scheme and engineering decision. It has shown that the degrees of reliability of foundation bearing capacity are more sensitive to the internal friction angle compared with the unit weight and the cohesion. The width or area of foundation can be decided upon in terms of the required factor of safety, degree of reliability and probability of failure. Moreover, the combined coefficients of variation of random variables will gradually decrease with the weights increasing of coefficients of variation based on the in-situ investigation results; the corresponding degrees of reliability will increase and the probabilities of failure decrease due to that decrease of combined coefficients of variation.