基于贝叶斯-粒子群优化算法的污染场地隔离墙阻隔效果CPTU原位评价方法

In-situ evaluation of barrier performance of cutoff wall based on Bayesian-Particle swarm optimization using piezocone penetration test

新建隔离墙投入使用前应进行质量检测以确保防渗性和均匀性。对其进行快速评价的难点在于高质量采样困难,室内试验耗时长。采用了孔压静力触探(CPTU)测试技术对新建隔离墙进行原位快速评价。通过对超孔隙水压力和水平渗透系数进行相关性分析,考虑参数空间变异性,应用随机场理论进行建模,模型参数定量描述了防渗缺陷层产生的原因。采用贝叶斯方法与粒子群算法相结合对模型参数进行求解,实现利用超孔隙水压力数据对新建隔离墙防渗缺陷层的快速识别和缺陷原因的定量评价。通过与传统的基于Robertson土体行为类别(SBT)分类方法的分层结果进行对比,指出传统土分类方法在隔离墙防渗评价中的不适用性。最后,结合CPTU孔压消散试验结果,评估新建隔离墙的连续水平渗透系数剖面。结果表明,提出的采用超孔隙水压力数据的CPTU原位评价方法可以正确识别新建隔离墙的防渗缺陷层并定量反映其原因。分析结果可为制定隔离墙修复计划提供指导信息。

Hydraulic impermeability and homogeneity should be ensured before the newly built cutoff walls put into operation.The difficulties of the rapid evaluation of the cutoff walls lie in the high-quality sampling and timeconsuming laboratory testing.In this study,piezocone penetration test(CPTU)is used to evaluate the barrier performance of a newly built cutoff wall.Based on the correlation analysis between excess pore water pressure and horizontal permeability coefficient,the random field theory is used for modeling,and the model parameters are defined to quantitatively describe the impermeability defects.Bayesian approach combined with particle swarm optimization is used to solve the model parameters,which realizes the rapid identification of impermeable defect layers and quantitative characterization.Comparing with the stratification results of traditional Robertson soil behavior type(SBT)method,the inapplicability of SBT method in evaluating the goodness of cutoff wall is pointed out.Finally,combined with the CPTU pore pressure dissipation test results,the continuous horizontal permeability coefficient profile of the cutoff wall is evaluated.Results show that the proposed CPTU in-situ evaluating method based on the excess pore water pressure can identify the impermeable defect layers and quantitively reflect its causes.The analysis results can be used as guiding information for making remediation plans.