SUBSIDENCE OF THE FOUNDATION GROUND PREVIOUSLY INDUCED INTERNAL EROSION

Abstract

Levees and the beneath foundation ground sometimes cause consolidation settlements. When the consolidation estimation is underestimated in advance, the structures and residents are damaged by consolidation. In addition, levees are subjected to piping and boiling with heavy rainfalls, which often have coarse permeable layers. The seepage is concentrated through coarse permeable layers. Owing to the repetition of regular rainfall and the changes in water levels, internal erosion occurs between a permeable and a finer soil layer. This study aims to reveal the effect of internal erosion on consolidation. Clay, including granular soil, is used to simulate both internal erosion and consolidation. First, long-term seepage is imposed on a soil specimen with a coarse layer. Then, clayey soil samples are obtained from the specimen subjected to seepage, and a consolidation test is conducted. The soil properties related to consolidation are revealed in several experimental cases. A numerical analysis is conducted using the experimentally obtained parameters to simulate the consolidation for embankment construction. Finally, the influence of internal erosion on consolidation is discussed. The soil consolidation behavior is similar to that of the clayey material when the specimen is loosely compacted. However, the behavior of the dense material appears to be sandy; consolidation is rapidly completed. The loosening caused by internal erosion is dissipated, and the consolidation properties approach those of the soil sample with a similar initial compaction degree. Finally, a practical application method for the internal erosion effect is proposed.