Design approach for rockfall protections with simple drapery systems

Abstract

Simple drapery systems are composed of a steel mesh held by a top longitudinal cable fixed with an anchoring system. They are simple, fast and cost effective rockfall protection remediation. Moreover, they can be used on any kind of slope. Their main use is on rocky slope with a steep gradient (higher than 45º). The goal of these interventions is to control the falls of the rocks, which are driven toward to the toe of the slope with slow velocity and low energy. The falling blocks, generally with a diameter up to 1.0 m, are then collected and pile up into a trench (or into a “pocket of mesh”). Because of the highly variable nature of rockfall behaviour these structures cannot be standardized, but they have to be analyzed and designed for each case. Maccaferri has developed a new calculation procedure (MacRO 2) as a practical tool to define the mesh and the related supporting structure composed by up-slope cable and anchors. This paper analyses the theoretical aspects at the base of the analysis for a simple drapery installation, the main steps used for the calculations, and presents a case study in Québec (CAN).