Debris flow hazard mitigation: a simplified analytical model for the design of flexible barriers

A channelized debris flow is usually represented by a mixture of solid particles of various sizes and water flowing along a laterally confined inclined channel-shaped region to an unconfined area where it slows down and spreads out into a flat-shaped mass. The assessment of the mechanical behavior of protection structures upon impact with a flow, as well as the energy associated to it, are necessary for the proper design of such structures which, in densely populated areas, can prevent victims and limit the destructive effects of such a phenomenon. In the present paper, a simplified analysis of the mechanics of the impact of a debris flow is considered in order to estimate the forces that develop on the main structural elements of a deformable retention barrier. For this purpose, a simplified structural model of cable-like retention barriers has been developed - on basis of the equation of equilibrium of wires under large displacement conditions, - and the restraining forces, cable stresses and dissipated energies have been estimated. The results obtained from parametric analyses and full-scale tests have then been analysed and compared with the proposed model.