Abstract

Very often the situation is presented in which the instability causes landslides of rocky blocks in areas that get in the access path of access to the orebody, which is almost impossible to stabilize. Then there is no more way out than to allow the rockfall to occur, of course, looking for possible solutions for their containment and / or reduction, as the fragments that generally fall can reach high speeds and kinetic energy, which makes the phenomenon extremely dangerous and complex to face. Mining operations are increasingly faced with achieving the operational safety ideal of zero harm, while at the same time increasing productivity. The implementation of approved mitigation measures against rockfall in opencast mines is becoming very common, due to the fast installation and cost-effectiveness of such measures. According to the guidelines for rockfall barriers, mines can rely on the approval issued by the EOTA (European Organisation for Technical Assessment). Liability insurance is issued by the suppliers, who guarantee the function of their rockfall barrier systems. In many cases the pit design can be optimized by increasing the slope inclination or reducing the berm width. The solution at Mandai Quarry located at Mandai District in the northern part of Singapore, will be presented in this paper, as a case study.

1.
Introduction
1.1
Rockfall barriers

Rockfall belongs to gravitative natural hazard processes and endanger frequently human life, infra-structure and settlements. One of the last rockfall events happened some month ago at a main road from Austria to Italy at the Reschenpass causing a fatality as the car was hit (see figure 1).

The rockfall event was much larger than the existing rockfall barrier capacity, thus the barrier could not stop the block and it got severely damaged. It was a small rockslide with an estimated volume of around 80 m3 according to the analysis of the geologist experts. The specialist responsible of taking protective measures face, the following problems:

  • Difficulties in predicting the possible areas from which the landslides originate and the possible trajectories of the fragments

  • The dimensions of the type block, as well as the energy with which they can reach the access path or the area where they are intended to brake blocks.

  • The influence that may be exerted by the material from which the own slope, on which the detachment occurs and which will obviously influence the speed trajectory of the rocks.

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