This paper presents a rock-fall impact calculation of a flexible barrier used in an open pit mine. The design of this barrier is based on the barrier prototypes tested according to the European Standards (ETAG 027 guidelines). These prototypes have successfully met the guidelines and now have official ETA approval and CE marking. A series of quasi-static tests on flexible chain-link net specimens and small-scale impact tests were carried out to check the material model assumptions and to calibrate the input data. Furthermore, a prototype of one of the ETA barriers was numerically simulated. The calculations are performed with Abaqus/Explicit 6.12. The rock-fall barrier model accounts for many complex physical processes that occur during the rock-fall stopping process: high-speed impact, contact with sliding friction and strain-rate dependent material behavior. The match between the simulation results and the test results allowed us to assess numerically a rock-fall barrier prototype specially developed for mining applications.

1 Introduction

Flexible steel wire-net rock-fall protection systems main components are: ultra-high strength (UHS) steel wire nets supported by spiral rope steel cables with inelastic brake elements and steel posts. They are used to stop falling rocks in mountain regions in order to protect people and infrastructure.

The rock-fall system investigated in this paper has been tested according to the European Standards (ETAG027, 2008).The fulfillment of the standards has allowed the manufacturer to obtain the CE marking of the product. This paper presents results of a FE simulation of the kinetic maximum energy level (MEL) test carried out in Walenstadt (SG, Switzerland).The MEL to which the barrier prototype was tested is equal to 502 kJ, which corresponds to a 1590 kg impactor with 25.12 m/s velocity at contact.

The numerical results are compared to the test data. The agreement of the simulation results allowed us to adapt the system for a mining application in Sishen, South Africa. Rock-fall events in open-pit mines occur mainly on steep pit walls without berms. However, in order to increase the profitability of the mines, the berm width can be decreased when installing rock-fall protection barriers on the berms (Balg et al. 2012).

The investigated prototype intercepting structure consists of a chain-link net, composed of wire bundles which are in contact to each other. The mechanical behavior of these nets has been studied by performing quasi-static tensile tests and impact tests (Von Boetticher 2012). The numerical approach used on this paper relies on the general contact algorithm of the FE Abaqus/explicit code (Abaqus Analysis User's Manual).

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