Author(s)

C. MARTINEZ, R. GARCIA-MARTINEZ & F. MIRALLES-WILHELM

Abstract

We present a quasi three-dimensional numerical model to simulate debris flows that considers a con-tinuum non-Newtonian fluid phase for water and fine sediments, and a non-continuum phase for large particles such as boulders. Particles are treated in a Lagrangian frame of reference using the 3D Discrete Element Method. The fluid phase is implemented in the RiverFLO-2D model, which solves the 2D depth-averaged shallow water equations with the Finite Element Method on a triangular non-structured mesh. The model considers particle–particle and wall–particle collisions, taking into account that particles are immersed in a fluid and subject to gravity, friction and drag forces. Bingham and Cross rheological models are used for the continuum phase providing very stable results, even in the range of very low shear rates. Results show that Bingham formulation proves better able to simulate the stopping of the fluid when the applied shear stresses are low. Comparing numerical results with analytical solutions and data from flume-experiments demonstrates that the model is capable of replicating the motion of large particles moving in the fluid flow. An application to simulate debris flows that occurred in Northern Venezuela in 1999 shows that the model can replicate the main boulder accumulation reported for that event.

Keywords

boulder accumulation, debris flow, discrete element method, finite element method, Lagrang-ian formulation