基于贝叶斯更新和信息量分析的边坡钻孔布置方案优化设计方法

为在节省岩土工程勘察成本的前提下获得最有价值的现场试验数据,通常需要事先设计最优的工程勘察方案。提出了基于贝叶斯更新和信息量分析的边坡钻孔布置方案优化设计方法,其中采用贝叶斯方法更新空间变异土体参数统计特征和计算边坡后验失效概率,在此基础上进行场地信息量分析确定边坡最优钻孔位置和最佳钻孔间距。此外,为更加准确地表征土体参数的先验信息,发展了非平稳随机场模型以表征土体参数均值和标准差随埋深逐渐增加的特性。最后通过一个不排水饱和黏土边坡算例验证了提出方法的有效性。结果表明:所提出的方法能够在现场勘察试验之前仅利用现有的土体参数先验信息有效确定边坡最优钻孔位置和最佳钻孔间距。对了解边坡稳定性能所需的试验数据,并不是钻孔间距越小所获得的信息量越大。

Optimization design approach for layout scheme of slope boreholes based on Bayesian updating and value of information analysis

To obtain more valuable site-specific test data with the minimal site exploration effort, it is of great significance to design an optimal site exploration program before geotechnical site investigation. This paper aims to propose an optimization design approach for layout scheme of slope boreholes based on the Bayesian updating and value of information analysis. The BUS (Bayesian updating with structural method) with subset simulation is employed to update the posterior statistical properties of spatially varying soil properties and to estimate the posterior probability of slope failure. Then, the value of information analysis is used to determine the most optimal borehole locations and separation distances between two boreholes. Additionally, to accurately characterize the prior information of soil parameters, a non-stationary random field model is developed wherein the depth-dependent nature of soil parameters is addressed. Finally, a clay slope example under undrained conditions is investigated to demonstrate the effectiveness of the proposed approach. The results indicate that the proposed approach can effectively determine the most optimal borehole locations and separation distances between two boreholes prior to performing site investigation tests based on the prior information of soil parameters. To design a separation distance between two boreholes as small as possible during geotechnical site investigation is not necessarily the best choice to understand the performance of the slope.