Modelling Internal Erosion with the Material Point Method

Internal erosion is a general term referring to the mechanism of detachment and movement of soil grains due to water flow through a porous media. It includes many different processes such as piping, soil contact erosion, or suffusion. The study and prediction of these complex phenomena is a recurrent topic in many different fields such as geotechnics, hydraulic and hydrocarbon engineering. This is because internal erosion is one of the main causes of failure of water retaining structures such as dikes and dams. This process also controls the amount of sand production in oil-producing wells. In many cases, such instabilities are related to large deformation of the material involved. The goal of this study is to present a first approach using the Material Point Method to model internal erosion process that occurs in bimodal internally unstable soils. These type of soils consist of a mixture of coarse and fine grains, in which the coarse fraction forms the stable skeleton of the soil, whilst fine grains can be eroded and are able to move freely as a result of seepage flow. The results of a simple numerical test consisting of a soil column subjected to a vertical flow of water are presented. It can be seen that fine fraction is eroded from the solid skeleton depending on the erosion law, and it transported as fluidised material through the saturated porous media.