Numerical Modelling of Seismic Activity at Tabular Orebody Mines in South Africa using the Boundary Element Method

The deep gold mines that extract the tabular orebodies of the Witwatersrand Basin in South Africa are generally considered to have the highest seismic hazard in the world, and large seismic events at these mines often produce strong ground vibrations that pose risks of damage to mining excavations, injury to mineworkers and even loss of life. Although most underground mines in South Africa have seismic monitoring systems with sufficient accuracy and sensitivity, prediction of large seismic events is still not possible, and therefore forecasting of seismic activity and management of the corresponding risks can probably only be facilitated through appropriate applications of numerical modelling. However, the recent efforts to develop and implement these methodologies have been particularly limited in South Africa. This dissertation develops and implements a novel and robust methodology for numerical modelling of seismic activity using the Boundary Element Method and presents several applications at tabular orebody mines in South Africa, including a comprehensive case study of the shaft pillar extraction at Bambanani Mine that spans more than ten years. In these numerical models, the mining excavations and the weaknesses in the surrounding rockmass that correspond to possible seismic sources are represented by displacement discontinuity elements, and the corresponding failure thresholds are evaluated using the Limit Equilibrium Method and Coulomb-friction, Hoek-Brown and Mohr-Coulomb strength criteria. Unlike other methodologies that only accommodate fault-slip seismic events on geological features, the proposed methodology also accommodates crush and shear seismic events ahead of the mining face, including Ortleppshears that are particularly common at the deep gold mines in South Africa. The rockmass deformation associated with these seismic sources is expressed as seismic potency in the numerical models which facilitates adequate calibration of the input parameters using the seismic source parameters of seismic events recorded by seismic monitoring systems. This dissertation demonstrates that the proposed methodology is generally appropriate for numerical modelling of seismic activity at underground mines that extract the tabular orebodies of the Carletonville, Klerksdorp and Welkom gold fields and provides some quantification of the computational errors associated with practical applications at these mines. Although the computational errors for medium- and long-term forecasting of seismic hazard are demonstrated to be acceptably low, short-term forecasting of seismic hazard is not addressed in this dissertation and therefore not recommended. The novel contributions in this dissertation provide opportunities for further efforts to develop and implement numerical modelling methodologies that reduce the risks of damage, injury and loss of life at underground mines in South Africa.

Grantor dc:publisher

Stellenbosch : Stellenbosch University

Year dc:date.issued

2026

Author dc:creator

• Gerber, Jacques Dewald

Advisor dc:contributor.advisor

• De Koker, Nico

Language dc:language.iso

en

Repository record dc:identifier.uri

https://scholar.sun.ac.za/handle/10019.1/136011

OAI identifier oai:identifier

oai:scholar.sun.ac.za:10019.1/136011