Document Type

Conference Paper

Publication Date


Publication Details

This conference paper was originally published as Gallagher, R, Research Needs in Regard to Design, Performance Criteria, Construction, Maintenance Assessment and Repair of Coal Mine Seals, in Aziz, N (ed), Coal 2005: Coal Operators' Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy, 2005, 307-314.


Legislation introduced for Queensland and New South Wales Coal mines provides different levels of prescription regarding specification of mine seals – generally in relation to capacity to withstand overpressure. In Queensland, the Coal Mining Safety and Health Regulation (2001), Section 341 (d) places a further onus on the statutory ventilation officer to ‘ensure all ventilation control devices at the mine are properly constructed and maintained’ and that the ventilation officer ‘must ensure a ventilation control device mentioned in the regulation … and installed at the mine meets the design criteria stated’ for the ‘type of device’. There is limited or no prescription in regard to: • standards and methods for design; • standards and methods for testing of seals in the ‘lab’ and relating results to field conditions (albeit limited recognised standard test facilities exist); • standards and methods for testing of seals in the field; • requirement to consider specific product types in light of the particular application and specific locational environment; • site selection for the seal; • consideration of the operational environment of the seal; • consideration of potential water head applied to the seal; • control and state of the ground surrounding the seal; • testing/acceptance criteria for a given seal, identification of defects in installation eg filling voids, etc (other than generic product tests in regard to overpressure/leakage, which may or may not bear relevance to the specific coal mine application, environment and service duty); • seal leakage limits (although NSW uses the term ‘airtight’); • requirement for and systems to maintain the seal, whether at design rating or otherwise; • guidance in regard to criteria for decisions to repair or identify the need to replace seals; • acceptable and effective methods to complete repair of seals; and • need for methods to assess effectiveness of repair in regard to both leakage and overpressure rating. Based on the experience of the author, it appears that risk management and life cycle approach to seals has not been adopted to the same extent as for other aspects of operations. Further, because of the number of disciplines and personnel involved that may influence various factors affecting seal integrity, the opportunity for oversight or unclear allocation of responsibility is considerable. While suppliers can provide explosion or design rated seals, this should only be a starting point for application of the product in a coal mine. Application is often considered by mine planning staff (taking into consideration mine environment parameters such as water, control of gas, spontaneous combustion risk, etc) in conjunction with the colliery ventilation officer, and then construction completed by contractors under supervision of operational staff. After construction, seals often are managed by operational personnel with input from the ventilation officer. Input of the geotechnical engineer into pillar design, roadway opening size, ground support specification and most stable seal location is also required. The need for a customised design approach for each seal site is proposed in order to take into account the many and variable factors that may influence a site so that improved seal performance reliability and predictability can be developed. A program of quantitative as well as qualitative monitoring of performance and triggers for rectification or maintenance action is required, and would provide support to the aforementioned proposal. Many mines rely on visual/audible inspection and periodic bag sampling as the primary means of assessment. Other significant factors such as seal material properties, rib degradation, convergence, floor heave, effects of water on both structural integrity of the seal as well as the air tightness of the seal do not generally receive the same level of attention. Based on the above observations, the author has compiled a reference checklist in regard to the above matters, including aspects of and approaches to mine and pillar design, geotechnical modelling and data collection, civil engineering design, site evaluation and practical options available. It is apparent that while some research has in isolation examined issues such as overpressure resistance, leakage performance, seal materials, rib sealing, effects of longwall mining and assessment of seal construction and integrity, further research may be required to deliver answers to many of the issues identified above to assist the industry and service providers develop and improve standards.