基盤の地盤特性が異なる河川堤防の高水位の継続作用による漏水とパイピングの進行特性

抄録

A river levee of the Yabe River was breached due to piping failure induced by prolonged high water levels following heavy rains in Northern Kyushu in 2012. The piping failure was caused by water infiltration into the highly permeable sand and gravel foundation under the clay levee body. However, some levees with similar foundations were deformed but did not fail. This study used models to investigate the influences of the soil-stratum conditions on the properties of pore water pressure propagation and water leakage and the piping failure behavior. The test results revealed that the piping could not be viewed as a single homogeneous foundation ground with leakage of clean water, according to Darcy's law. Rather, the piping failure progressed with a large water leakage including sand in a two- layer foundation ground consisting of gravel below fine sand, even under a low hydraulic gradient. We propose a new criterion for piping based on the foundation ground strata configuration, average hydraulic gradient, and flow velocity.