New simple method for calculating impact force on flexible barrier considering partial muddy debris flow passing through

Abstract

Flexible barriers trap large particles and boulders in debris flow but allow slurry and small particles to pass through. Field tests and real cases indicate that a certain amount of slurry and small particles in debris flow passes through a flexible barrier with residual velocities. In the design of flexible barriers for debris flow mitigation, accurate determination of the impact force is the key issue. Nevertheless, a few of the current simple methods have quantified the effect of passing through on the impact force reduction. Without considering the passing through of slurry, impact loading can be tremendously overestimated. In this study, a new simple method considering the passing through of slurry is proposed based on a two-phase flow model. This method is verified by the measured impact forces of two large-scale physical modeling tests. In the tests, debris flows with different water contents in mass (89.4% and 61.1%) were initiated to affect a flexible barrier. The volume of the retained debris and the velocity loss of the passing slurry in the two tests were measured. Furthermore, this proposed simple method is validated by the data from well-documented laboratory tests in the literature. Comparisons and validations lead to the conclusion that the proposed simple method provides an accurate and creative way to predict the dynamic impact force of muddy debris flow on a flexible barrier.