Rock Mechanics and Rock Engineering

, Volume 46, Issue 3, pp 515–526 | Cite as

Perforation of Flexible Rockfall Barriers by Normal Block Impact

  • J. P. HambletonEmail author
  • O. Buzzi
  • A. Giacomini
  • M. Spadari
  • S. W. Sloan
Original Paper


Flexible rockfall barriers are a common form of protection against falling blocks of rock and rock fragments (rockfall). These barriers consist of a system of cables, posts, and a mesh, and their capacity is typically quantified in terms of the threshold of impact (kinetic) energy at which the barrier fails. This threshold, referred to here as the “critical energy,” is often regarded as a constant. However, several studies have pointed out that there is no single representative value of critical energy for a given barrier. Instead, the critical energy decreases as the block size decreases, a phenomenon referred to as the “bullet effect.” In this paper, we present a simple analytical model for determining the critical energy of a flexible barrier. The model considers a block that impacts normally and centrally on the wire mesh, and rather than incorporate the structural details of the cables and posts explicitly, the supporting elements are replaced by springs of representative stiffness. The analysis reveals the dependence of the critical energy on the block size, as well as other relevant variables, and it provides physical insight into the impact problem. For example, it is shown that bending of the wire mesh during impact reduces the axial force that can be sustained within the wires, thus reducing the energy that can be absorbed. The formulas derived in the paper are straightforward to use, and the analytical predictions compare favorably with data available in the literature.


Rockfall barrier Impact Kinetic energy Bullet effect Finite element Analytical 



Financial support provided by the ARC Centre of Excellence for Geotechnical Science and Engineering (grant number CE110001009) is gratefully acknowledged. The first and last authors would also like to acknowledge support provided by the ARC Laureate Fellowship entitled “Failure Analysis of Geotechnical Infrastructure” (grant number FL0992039).


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Copyright information

© Springer-Verlag Wien 2012

Authors and Affiliations

  • J. P. Hambleton
    • 1
    • 2
    Email author
  • O. Buzzi
    • 2
  • A. Giacomini
    • 2
  • M. Spadari
    • 2
  • S. W. Sloan
    • 1
    • 2
  1. 1.ARC Centre of Excellence for Geotechnical Science and EngineeringThe University of NewcastleCallaghanAustralia
  2. 2.Priority Research Centre for Geotechnical and Materials ModellingThe University of NewcastleCallaghanAustralia

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