基于极差理论的基桩承载力可靠性分析

Reliability Analysis of Bearing Capacity of Pile Based on Range Theory

由于经济和工期原因,基桩的静载荷试验数据往往很少,并且数据的离散性很大,大大增加了承载力可靠度分析的难度。本文利用数理统计中的极差理论,根据静载试验结果,计算出总体样本的均值和方差。并利用一次二阶矩法,给出了基桩竖向承载力服从对数正态分布时的可靠度计算方法。最后,根据国内外相关规范和文献资料,选取目标可靠度指标3.2作为基桩承载力的目标可靠度指标,以此衡量桩基的质量是否满足工程需要。算例分析表明,该方法的计算精度满足工程需要,可为桩基设计人员根据实测结果确定设计值提供参考,同时也为相关规范的修订提供参考。

Due to cost and construction period of a project,the data from static load test of pile are insufficient and the dispersion degree is very large,which brings more difficulties to reliability analysis of bearing capacity.In this paper,the mean and variance of population sample are calculated based on the concept of range extremity difference and the result from static load test.Meanwhile,based on the first order second moment method,the calculation formula of reliability is presented under the condition that the bearing capacity of pile follows lognormal distribution.After that,according to worldwide specifications,codes and papers,a target reliability index of 3.2 is proposed as the target reliability index of the bearing capacity of pile to evaluate whether the quality of pile foundation meets the requirements of the project.The results from case studies show that the calculation accuracy is satisfactory and it is valuable for designers to determine the design parameters according to testing piles,and it can also be used as a reference for further revisions of relevant standards.