Debris Flow Impact on Rigid Walls: Protection by Tree Trunks

Abstract

To mitigate debris flow disasters, most of the previous research has focused, mostly through experimental methods, on placing different rigid barriers as structural prevention against debris flow to dissipate its energy. However, there has been less research on simulating the debris flow resistance on the tree trunk patches. In the present work, analytical and numerical simulation of the peak impact pressure of debris flow on a vertical rigid wall has been analysed under the protection of a patch of tree trunks. Along the debris flow path, tree trunks with identical diameters have been arranged in linear and rectilinear configurations. The mathematical analysis employs the Reynolds Transport Theorem, while the numerical simulations use the Reynolds-Averaged-Navier-Stokes equations. The numerical simulation results have depicted that the rectilinear configuration of tree trunks in each spot area is more effective than other configurations and increasing density of tree trunks within a given spot area is 50% more protective than the increasing the number of rows of the tree trunks. Additionally, this study estimates a new dynamic coefficient (alpha) as a function of the Froude number and devises a new expression for the drag force coefficient for different tree trunk configurations.