Impact of Granular Masses on Sheltering Structures: Definition of the Initial Conditions for the Assessment of Impact Forces

In the engineering practice, in the design of sheltering structures against flow-like landslides, empirical formulas are still commonly employed to estimate the maximum force transmitted by the impacting mass to the structure. In recent years, the development of robust numerical codes, capable of dealing with large displacements, have allowed to simulate the dynamic interaction between flowing granular masses and obstacles and to derive new formulas for a more rational design of protective structures. Nowadays, the propagation phase and the impact are analyzed separately and the initial conditions (initial Froude Number and porosity) for the numerical simulation of the impact are the result of a previous propagation analysis. In this work, a theoretical discussion about such initial conditions is done, taking advantage of what predicted by a simplified rheology for dry granular materials, taking into consideration the role of porosity in affecting the maximum impact force transmitted to the sheltering structure to be designed.