Installation of lattice girders with Toussaint–Heintzmann yielding elements in poor ground conditions

Authors: Belov, O; Roberts, T; Ma, KJ; Ooi, J; Baasanjav, B Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2325_46

Cite As:
Belov, O, Roberts, T, Ma, KJ, Ooi, J & Baasanjav, B 2023, 'Installation of lattice girders with Toussaint–Heintzmann yielding elements in poor ground conditions', in J Wesseloo (ed.), Ground Support 2023: Proceedings of the 10th International Conference on Ground Support in Mining, Australian Centre for Geomechanics, Perth, pp. 667-682, https://doi.org/10.36487/ACG_repo/2325_46



Abstract:
In block cave mines, the permanent life of mine tunnels are required to withstand multiple changes in ground stresses and remain functional for up to several decades. In block cave mines, in general, the changes in ground stresses originate from initial induced stresses during tunnels and chamber excavations. Following this is an increase in abutment stresses due to undercut front advancement phase. Further increase in abutment stresses occurs due to cave growth and upward propagation. Then, the abutment stress reduction takes place due to the cave breakthrough to the surface. It should be noted that at some mines, the ground stresses may increase due to cave material re-compaction or due to remnant pillar loading if undercutting was not carried out properly. As a matter of good practice, the key requirement for a block cave mine permanent infrastructure, such as an ore handling system, is to have it excavated and fitted out before the start of the undercutting phase. Multiple changes in ground stresses are likely to cause large deformations in the tunnels and pose challenges to ground support designs with the choice of ground support/reinforcement types/systems/elements, particularly if the permanent infrastructure is situated in the poor ground due to the presence of large weak structures. At Oyu Tolgoi mine, the tunnel stability of the haulage level is very important for the uninterrupted movement of payload trucks delivering ore from truck chutes to crusher chambers. Affected by changes in abutment stresses and poor ground conditions in certain sections of the tunnels, excessive drive deformations are expected throughout the several decades of mine life in the haulage level requiring innovative ground support/reinforcement design involving installation of fibrecrete embedded lattice girders with yielding elements.

Keywords: steel arch, lattice girders, yielding elements, poor ground, innovative design, block cave, permanent tunnelling infrastructure

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