The appearance of mud islands, termed mudlumps, is well known in the Mississippi River delta mouths. A similar phenomenon occurred at the mouth of the Iinashi River in 1991. Although several theories have been proposed to explain the formation processes of these phenomena, there are many unclear points in the deformation behavior of soft ground from the accumulation of sandy sediments during the formation of mudlumps. However, due to advances in both constitutive equations which can explain mechanical behavior of soil and reasonable soil parameters, as well as advent of new generations of powerful computers, it has become possible to predict the deformation behavior of soft ground using finite element method.
This paper presents finite element analysis of mudlump formation caused by sand accumulation using an elastoviscoplastic model. The formation process of mudlumps is explained quantitatively by comparing results of finite element analysis with information based on sedimentary environments such as key layers. Finally, this study demonstrates the importance of integrated studies of sedimentary environments and geotechnical engineering of natural phenomenon where little information on deformation behavior exists.