New Design Software for Rockfall Simple Drapery Systems

Rockfall drapery systems are commonly used as simple, fast and economical measures to control rockfall trajectories on very steep slopes. The systems basically consist of a steel mesh attached at the slope crest with a longitudinal cable fixed by means of a suitable number of ground anchors. The effect of this kind of intervention is to control the trajectory of falling rocks, which then fall to the bottom of the slope with a slower velocity, or are stabilized in place. They can be used on any kind of slope to protect sensitive targets in the mining industry, roads and railways, and inhabited areas. The falling blocks, typically smaller than 0.6 - 1.0 m in diameter, pile up into a trench (or into a “pocket of mesh”) at the bottom. In comparison to other types of rockfall protection measures, the simple drapery is cheaper, and its maintenance is easier. On the other hand, it cannot be considered a remedy for shallow instability because it can only control the trajectories of falling rocks and facilitate their collection at the slope toe. The design of simple draperies requires the analysis of several factors such as slope features (height, gradient, morphology), the geological and dynamic features (nature of the ground or rock, type of instability, erosion problem, blocks size), the environmental condition (presence of vegetation, aesthetic concerns), the installation problem (access to the slope, safety for the workers, safety for the surrounding areas) and finally the performance required (temporary or permanent intervention, required maintenance, cost). Finally the most problematic design-step is the choice of a suitable mesh, the top longitudinal cable, and the top anchor type. Because of the highly variable nature of rockfall behavior, these structures cannot be standardized - they have to be analyzed and designed for each application. A new software application (MacRO 2) has been developed with a practical tool to define the mesh and the related supporting structure consisting of up-slope cables and anchors. The software allows designers to size the top longitudinal cable, the anchors, and select the appropriate mesh drapery and establish for maintenance procedures. Even if the method seems quite simple and rough, it is effective and lets the designer correctly select drape materials and the geometry to be used on the systems. This paper analyzes the conditions for a simple drapery installation, the main steps used for the calculations, and presents a case study at a mine in the U.S.. Nevertheless, even if the software allows for a quick and simple calculation approach, onsite observations are always recommended in order to achieve a good design, with the ultimate goal of protecting property and human lives.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: pp 376-393
  • Monograph Title: Proceedings of the 64th Highway Geology Symposium (HGS 2013)

Subject/Index Terms

Filing Info

  • Accession Number: 01644037
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Aug 14 2017 6:45PM