Rock face stability is of major importance in quarrying. Temporary faces must have adequate short-term stability to allow safe working and ﬁnal faces must have long-term stability to allow safe access for restoration, landscaping or any future usage. Such requirements mean that temporary faces may have design lives varying from weeks to months and ﬁnal faces 100 years or more. Management of stability in both the short and longer term is extremely important.
ESP have extensive experience of investigation in advance of quarry-planning and/or extension. We commonly occupy the role of Geotechnical Specialist (Regulation 32 Quarries Regulations 1999) and perform Geotechnical Assessments for identified significant hazards (Regulation 32 HSE 2014).
Rock masses are notoriously variable and detailed information on the geotechnical conditions on which temporary and ﬁnal face design can be based can be diﬃcult and expensive to obtain.
The resultant face design is therefore a compromise that, although optimising stability in terms of predicted geotechnical conditions at depth, seldom guarantees face stability.
Stability is also a function of the method of excavation and can be reduced considerably where high explosives are used.
Initial face designs are therefore updated and improved during excavation as more information on the rock mass is obtained. Even then, geotechnical variability within the host rock often means that designed faces, particularly short-term working faces, can be locally unstable or develop instability with time (Matheson & Reeves, 2011).
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Quarries are inherently hazardous environments, requiring oversteepening of faces by excavation through emerging geotechnical conditions. Tip management is also extremely important to adequately manage stability in both the short and longer term. The Quarries Regulations and Approved Code of Practice provide guidance on design and management requirements, including roles and responsibilities for key persons, and the overall process.
G.D. Matheson and G.M. Reeves. 2011. The identification, appraisal and assessment of hazards on quarry rock faces in terms of the UK Quarries Regulations. Quarterly Journal of Engineering Geology and Hydrogeology 2011, v.44; p259-275.
Health and Safety at Quarries – Approved Code of Practice and Guidance. HSE, 2014.
Regulation 32 Quarries Regulations 1999. Health and safety at quarries. The Quarries Regulations 1999. Approved Code of Practice, 2013.