Ground Support Design
Know Your Ground Support
Geotechnical Engineers across the world rely on effective ground support designs to ensure the stability of excavations. Ground support design can be separated into two categories; gravity- (quasi‑static) and seismic- (dynamic) designs.
Designing for gravity, as the name implies, is primarily focused on removing gravity-induced failures, and if required strengthening the rockmass. This type of ground support design is theoretically well understood, and failure is generally due to a lack of information on the condition of the rockmass or possible wedge formations.
Compared to a quasi‑static design, dynamic design is a much more complex process. Current understanding of the theoretical driving forces of rockbursts is ambiguous, which makes these designs generally ineffective. This is especially concerning as dynamic ground support is considered one of the most important control measures for seismically active mines (See the SRMP post for context).
The general practice for most seismically active mines is to follow the Canadian Rockburst Research Methodology (CRR); an updated version of this document can be found here.
This is a theoretical approach to dynamic support design, which is a reasonable methodology when you don’t have any in-depth information about the rockmass conditions. In more recent times it has been suggested (see Kaiser 2018) that dynamic ground support should be designed based on the expected/measured rockmass deformation, instead of the expected ground motion (see CRR) , but this is not widely practised.
For an increasing number of mines, these theoretical methods do not prevent rockburst damage. Most mines are forced to adopt the “if it fails, replace it” strategy. This is generally an informal process, which essentially comes down to if a component of the ground support system fails, replace it with something that can absorb more energy.
There are, however, several papers with empirical ground support methodologies to formalise this process more. I list a few of them for those who want to know a bit more:
From Mikula and Gebremedhin (2017)
From Morrisette and Hadjigeorgiou (2017
In recent years, the implementation of a probabilistic ground support design methodology has gained more traction as it becomes clear that current deterministic and empirical methods are deficient. Probabilistic ground support designs aim to describe the probable dynamic ground support performance based on the variability of the rockmass, the variation of ground support unit performances, the variability in stress conditions and the stochastic nature of seismicity.
At IGM Geotechnical we can provide you with expertise and experience in all aspects of ground support design. We also offer Dynamic Ground Support Testing Services if you have concerns about dynamic ground support performance. Contact us for all your underground geotechnical needs.