Evaluation of seepage resistance performance of river levees using fragility curves incorporating piping damage history

Abstract

During the heavy rainfall in northern Kyushu in July 2012, the Yabe River levee breached due to piping that occurred in a locally present sandy soil layer within the foundation ground. Ground surveys for river levees involve uncertainties due to the selection of survey cross-sections and survey density. This study proposes a method to reduce uncertainties in ground surveys by utilizing damage history and to construct fragility curves that reflect the actual seepage resistance performance of river levees. Specifically, seepage flow analyses are repeatedly conducted using statistically processed permeability, and their compatibility with damage history is verified. By excluding incompatible combinations of permeability and repeating calculations, the accuracy of seepage resistance performance evaluation for river levees is improved. The proposed method was applied to actual river levees and confirmed to adequately represent the damage history.