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The concept of design block size – A critical review of ONR 24810 “Technical Protection against Rockfall”
Author(s) -
Illeditsch Mariella,
Preh Alexander
Publication year - 2020
Publication title -
geomechanics and tunnelling
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.317
H-Index - 18
eISSN - 1865-7389
pISSN - 1865-7362
DOI - 10.1002/geot.202000021
Subject(s) - block size , rockfall , block (permutation group theory) , eurocode , computer science , geology , mathematics , engineering , landslide , structural engineering , geotechnical engineering , geometry , computer security , key (lock)
In Austria, the Guideline for “Technical Protection against Rockfall”, named ONR 24810 provides guidance to assess rockfall hazard (at object scale) by determining a so‐called design block size. The aim of this article is to critically review the concept of design block size and to suggest alternatives. The design block size is derived from a block size distribution and event frequency, both of which may be very uncertain. Modelling a single “constant” design block may result in trajectories far away from reality. The design approaches of ONR 24810 and Eurocode 7 are compared. A case study is presented and discussed. Reducing input parameters at the beginning of the design approach results in apparent characteristic energy levels and bounce heights, which are not characteristic, as defined by EC7. By disregarding all small and the biggest blocks, valuable information of maximum energy levels and bounce heights is lost. The entire block size distribution should be used for rockfall simulations, rather than a single block size. Fragmentation should be considered, if applicable.