Fast, safe, and fully mechanized installation of high-tensile chain-link mesh for underground support

Abstract

The ever-increasing depth of mineral extraction presents a challenging environment for hard-rock underground mines. High in situ stresses and associated seismicity with potential rockburst hazards are the major decisive factors contributing to the choice of a ground support regime. Conventional ground support systems, designed primarily for static loads, are not always capable of providing safe working conditions for underground personnel in seismically active mines. Systems specifically developed to resist dynamic loading and allowing for larger deformations are therefore preferred alternatives. High-tensile chain-link mesh has a proven record of successful use in open cut operations in various rockfall barrier installations due to its high energy absorption capacity. It has also been used in underground operations in various parts of the world. Its application in South African underground mining, however, is limited due to the high labour intensity. This paper describes a method of mechanized installation of a chain-link mesh as evaluation at Gold Fields' South Deep Gold Mine situated some 45 km south-west of Johannesburg. A purpose-built mechanized roll mesh handler, developed in Australia, was used in this trial. The handler is compatible with all standard multi-boom underground drill rigs and is operated utilizing the hydraulic circuit normally used for the feed arrangement. A number of key performance indicators have been specified as success criteria by Gold Fields: <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">A 30% faster installation compared to the conventional methodology <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">The mesh should sustain any blast damage when applied to the blasting face <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">No unravelling of the mesh when cut <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">No failure of mesh under normal conditions <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Reliability of the MESHA® installation handler (availability >90%) <img width=32 height=32 src="../../../../../img/revistas/jsaimm/v112n2/a05icone01.jpg">Compatibility of the MESHA® installation handler with AC 282 boomers. Although the energy-absorbing mesh combined with yielding rockbolts is a ground support system of choice for rockburst-prone conditions, the operational upsides recognized during the trial imply that this product can also be competitively used in less demanding ground conditions where weld mesh or shotcrete are customarily used as a primary surface support.