A quarry facing a large-scale wedge failure risk needed to understand exactly how far the problem extended - and what it would cost them.
Project
A small quarry operating within a Greywacke deposit identified a potentially significant geotechnical risk. Numerous persistent discontinuities were present across the site, and a developing large-scale wedge failure was observed along one boundary. If failure occurred, it was expected to propagate beyond the site limits, potentially requiring the quarry to purchase neighbouring land at increased cost.
Data Acquired
A detailed structural mapping exercise was undertaken using a high-precision LiDAR unit. The high-resolution data allowed accurate identification of both large- and small-scale discontinuities. Each discontinuity set was assessed for its Factor of Safety, and where values fell below 1, or where the probability of failure was <2% for FoS <1 and 23% for FoS <1.5 (per Priest & Brown, 2006), these features were extrapolated to determine potential intersection points.
Analysis
The combined LiDAR and geotechnical assessment enabled a clear understanding of block geometries and the extent of possible wedge failures. The worst-case extent of a potential failure was mapped spatially, giving surveyors an accurate boundary for risk.
Conclusion
The improved understanding of failure geometry enabled the quarry to define the minimum amount of neighbouring land that would need to be purchased. This significantly reduced potential acquisition costs while maintaining site safety.
