A Dynamic Design Method for Rockfall Protection Galleries

Galleries are common structures to protect roads and railways from rockfall hazards. The design concepts in recent guidelines are based on the application of a static equivalent impact force. This approach is simple to use for practicing engineers. However, the dynamic behavior of the structure is not adequately taken into consideration. An analytical model based on a system of multiple degrees of freedom is proposed, which enables predicting shear and bending failure of the gallery due to the impact of a falling block of rock. Several simplifications allow numerically solving the basic equations by means of a spreadsheet. In large-scale tests reinforced concrete slabs, measuring 3,5 m × 4,5 m and with two different thicknesses, were subjected to increasing impact loads up to failure. The measured decelerations in the block and the reaction forces at the supports provide the required data to verify the analytical model. The evaluation of an existing structure shows that for dimensions of average Swiss galleries failure is governed by punching shear.