基于BCS-KL方法的地层边界不确定性研究

Uncertainty analysis on stratigraphic boundary based on BCS-KL method

在工程建设中获取的现场钻孔数据有限,利用钻孔数据解释地下地层不可避免地存在不确定性,进而影响桩基础等工程设计的可靠性。对此,提出了从有限钻孔数据中量化地层边界不确定性的方法,并研究地层边界不确定性对单桩竖向承载力特征值的影响。首先依据钻孔数据,通过贝叶斯压缩采样-KL展开(BCS-KL)方法重建地层边界,并生成大量随机场数据量化地层边界的统计不确定性;然后依据地层边界数据,对单桩竖向承载力特征值进行不确定性分析。分析结果表明:BCS-KL方法生成的大量随机场数据能很好地表征地层边界的不确定性;在钻孔间距较大时,单桩竖向承载力特征值在95%置信区间内相差4 660.88 kN,差距较大。通过BSC-KL方法科学评估地层边界不确定性对单桩竖向承载力的影响,对确保工程设计可靠性具有重要意义。

Due to the limited borehole data obtained during constructions,it is inevitable to interpret the underground stratigraphic boundary with uncertainty,which affects the design reliability of pile foundation and other engineering projects.In this paper,a method was proposed to quantify the uncertainty of stratigraphic boundary with limited borehole data,and the influence on the characteristic value of the vertical bearing capacity of a single pile was discussed.Firstly,based on the borehole data from a power plant,the stratigraphic boundary was reconstructed and a large number of random field data was generated to quantify the statistical uncertainty of the stratigraphic boundary by Bayesian compressive sampling-KL expansion(BCS-KL)method;then,according to the stratigraphic boundary data,the uncertainty analysis on the characteristic value of vertical bearing capacity of a single pile was carried out.The results showed that a large amount of random field data generated by the BCS-KL method can well characterize the uncertainty of the stratigraphic boundary;when the borehole spacing was sparse,the characteristic value of vertical bearing capacity of single pile has difference of 4660.88 kN in the 95%confidence interval,showing great difference.It is of great significance to evaluate the influence of stratigraphic boundary uncertainty on the characteristic value of the vertical bearing capacity of a single pile for engineering design by BSC-KL method.