Research Needs in Regard to Design, Performance Criteria,Construction, Maintenance Assessment and Repair of Coal MineSeals

摘要

Legislation introduced for Queensland and New South Wales Coal minesrnprovides different levels of prescription regarding specification of minernseals – generally in relation to capacity to withstand overpressure.rnIn Queensland, the Coal Mining Safety and Health Regulation (2001),rnSection 341 (d) places a further onus on the statutory ventilation officer torn‘ensure all ventilation control devices at the mine are properlyrnconstructed and maintained’ and that the ventilation officer ‘must ensurerna ventilation control device mentioned in the regulation … and installedrnat the mine meets the design criteria stated’ for the ‘type of device’.rnThere is limited or no prescription in regard to:rn?standards and methods for design;rn?standards and methods for testing of seals in the ‘lab’ and relatingrnresults to field conditions (albeit limited recognised standard testrnfacilities exist);rn?standards and methods for testing of seals in the field;rn?requirement to consider specific product types in light of thernparticular application and specific locational environment;rn?site selection for the seal;rn?consideration of the operational environment of the seal;rn?consideration of potential water head applied to the seal;rn?control and state of the ground surrounding the seal;rn?testing/acceptance criteria for a given seal, identification of defects inrninstallation eg filling voids, etc (other than generic product tests inrnregard to overpressure/leakage, which may or may not bear relevancernto the specific coal mine application, environment and service duty);rn?seal leakage limits (although NSW uses the term ‘airtight’);rn?requirement for and systems to maintain the seal, whether at designrnrating or otherwise;rn?guidance in regard to criteria for decisions to repair or identify thernneed to replace seals;rn?acceptable and effective methods to complete repair of seals; andrn?need for methods to assess effectiveness of repair in regard to bothrnleakage and overpressure rating.rnBased on the experience of the author, it appears that risk managementrnand life cycle approach to seals has not been adopted to the same extentrnas for other aspects of operations. Further, because of the number ofrndisciplines and personnel involved that may influence various factorsrnaffecting seal integrity, the opportunity for oversight or unclear allocationrnof responsibility is considerable.rnWhile suppliers can provide explosion or design rated seals, thisrnshould only be a starting point for application of the product in a coalrnmine. Application is often considered by mine planning staff (taking intornconsideration mine environment parameters such as water, control of gas,rnspontaneous combustion risk, etc) in conjunction with the collieryrnventilation officer, and then construction completed by contractors underrnsupervision of operational staff. After construction, seals often arernmanaged by operational personnel with input from the ventilation officer.rnInput of the geotechnical engineer into pillar design, roadway openingrnsize, ground support specification and most stable seal location is alsornrequired. The need for a customised design approach for each seal site isrnproposed in order to take into account the many and variable factors thatrnmay influence a site so that improved seal performance reliability andrnpredictability can be developed.A program of quantitative as well as qualitative monitoring ofrnperformance and triggers for rectification or maintenance action isrnrequired, and would provide support to the aforementioned proposal.rnMany mines rely on visual/audible inspection and periodic bag samplingrnas the primary means of assessment. Other significant factors such as sealrnmaterial properties, rib degradation, convergence, floor heave, effects ofrnwater on both structural integrity of the seal as well as the air tightness ofrnthe seal do not generally receive the same level of attention.rnBased on the above observations, the author has compiled a referencernchecklist in regard to the above matters, including aspects of andrnapproaches to mine and pillar design, geotechnical modelling and datarncollection, civil engineering design, site evaluation and practical optionsrnavailable.rnIt is apparent that while some research has in isolation examined issuesrnsuch as overpressure resistance, leakage performance, seal materials, ribrnsealing, effects of longwall mining and assessment of seal constructionrnand integrity, further research may be required to deliver answers to manyrnof the issues identified above to assist the industry and service providersrndevelop and improve standards.