Using 3D Slope Stability Analysis in an Open-cut Coal Strip Mine: A Case Study

DOI

10.2991/978-94-6463-900-1_50How to use a DOI?

Keywords

3D Slope Stability analysis; Softwall; Open-cut Coal Mining

Abstract

The softwall method for highwall stabilization is a widely adopted form of wall control in Australian open-cut coal mining. The softwall method typically involves blasting the overburden with the intention to fragment, rotate and disrupt discontinuities within the rockmass, and then digging it at a 45° batter to buttress the in-situ rock mass. This method was implemented in a pit with historical highwall instabilities, where a seam split, analogous to a monocline with the fold axis striking sub-parallel to the highwall, results in a section of coal to become pitward dipping. Coupled with unfavourable jointing, this has resulted in past toppling failures. A 45° softwall was implemented in the subsequent strip, which also failed due to weaker than expected strength of a weak layer within the coal seam, which could not be disrupted alongside the overburden due to the severe damage and dilution it would cause. The softwall batter angle was reduced even further from 45° until an acceptable factor of safety was calculated. However, data from production drilling of the subsequent strip revelated steeper coal dip than expected. 2D slope stability analysis resulted in an unacceptably low factor of safety and suggested that another redesign of the wall was required. Due to the 3D nature of the coal seam however, the 2D factor of safety was expected to be conservative. This was confirmed by undertaking 3D slope stability analysis, which confirmed that the 3D factor of safety is 25% higher than in 2D. Based on this, the initially planned softwall design was implemented, and verified to have performed well.

Copyright

© 2025 The Author(s)

Open Access

Open Access This chapter is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License (http://creativecommons.org/licenses/by-nc/4.0/), which permits any noncommercial use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made.

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TY  - CONF
AU  - Jiwoo Ahn
PY  - 2025
DA  - 2025/12/07
TI  - Using 3D Slope Stability Analysis in an Open-cut Coal Strip Mine: A Case Study
BT  - Proceedings of the Rocscience International Conference 2025 (RIC 2025)
PB  - Atlantis Press
SP  - 505
EP  - 512
SN  - 2589-4943
UR  - https://doi.org/10.2991/978-94-6463-900-1_50
DO  - 10.2991/978-94-6463-900-1_50
ID  - Ahn2025
ER  -