Xu, Z, Xu, H & Tun, D 2026, 'Assessment of temporary yielding slender sandstone pillars using staged FLAC3D modelling', in D Cumming-Potvin & J Wesseloo (eds), Ground Support 2026: Proceedings of the 11th International Conference on Ground Support in Mining, Australian Centre for Geomechanics, Perth, pp. 1-9, https://doi.org/10.36487/ACG_repo/2625_13
(https://papers.acg.uwa.edu.au/p/2625_13_Xu/)
Abstract: The design of slender rock pillars (width-to-height ratio <1.0) and their associated rockbolt support systems remains challenging because of reduced confinement, elevated stress concentrations and sensitivity to geological variability. This paper builds upon a previously published case study on the design of a temporary yielding pillar in massive sandstone by advancing the numerical assessment from a general stability evaluation to a detailed staged FLAC3D model that explicitly simulates the excavation sequence and installation of pattern glass-fibre rockbolts. The case study involves a temporary slender pillar located at the base of a shaft excavation approximately 100 m below ground level, where controlled yielding was adopted as the design philosophy to maintain excavation stability during construction. 
The staged numerical model provides improved insight into the progressive development of pillar deformation, stress redistribution, plastic strain localisation and bolt load mobilisation throughout the excavation sequence. Unlike the previous study, the modelling framework explicitly captures the interaction between the yielding pillar and the installed support, enabling assessment of bolt capacity utilisation and support performance under realistic construction conditions. The results identify localised zones of elevated strain and evaluate the effectiveness of the installed rockbolts in providing confinement and enhancing the residual load-bearing capacity of the temporary pillar. Based on these findings, the support layout is optimised to improve pillar performance and maximise the efficiency of the ground support system.

Keywords: slender pillar, yielding pillar, glass-fibre bolt, FLAC3D