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Influence of longwall mining on the stability of gas wells in chain pillars

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International Journal of Mining Science and Technology 2020年第1期30卷 3-9页

作者： Peter Zhang heather dougherty Daniel Su Jack Trackemas Berk Tulu CDC NIOSH Pittsburgh Mining Research Division(PMRD)PittsburghPA 15236USA Department of Mining Engineering West Virginia UniversityMorgantownWV 26505USA

Longwall mining has a significant influence on gas wells located within longwall chain *** subsidence and abutment pressure induced by longwall mining can cause excessive stresses and deformations in gas well *** the gas well casings are compromised or ruptured,natural gas could migrate into the mine workings,potentially causing a fire or *** the current safety regulations,the gas wells in the chain pillars have to be either plugged or protected by adequate coal *** current regulations for gas well pillar design are based on the 1957 Pennsylvania gas well pillar *** study provided guidelines for gas well pillars by considering their support area and overburden depth as well as the location of the gas wells within the *** the guidelines were developed for room-andpillar mining under shallow cover,they are no longer applicable to modern longwall coal mining,particularly,under deep *** well casing of failures have occurred even though the chain pillars for the gas wells met the requirements by the 1957 *** study,conducted by the National Institute for Occupational Safety and Health(NIOSH),presents seven cases of conventional gas wells penetrating through longwall chain pillars in the Pittsburgh Coal *** study results indicate that overburden depth and pillar size are not the only determining factors for gas well *** other important factors include subsurface ground movement,overburden geology,weak floor,as well as the type of the construction of gas *** modeling was used to model abutment pressure,subsurface deformations,and the response of gas well *** study demonstrated that numerical models are able to predict with reasonable accuracy the subsurface deformations in the overburden above,within,and below the chain pillars,and the potential location and modes of gas well failures,thereby providing a more quantifiable approach to assess the stability of the gas wells in l

关键词： Longwall mining Gas well Chain pillar Casing stability

Analysis of gateroad stability at two longwall mines based on field monitoring results and numerical model analysis

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International Journal of Mining Science and Technology 2019年第1期29卷 35-43页

作者： Gabriel S.Esterhuizen David F.Gearhart Ted Klemetti heather dougherty Mark van Dyke National Institute for Occupational Safety and Health

Coal mine longwall gateroads are subject to changing loading conditions induced by the advancing longwall face. The ground response and support requirements are closely related to the magnitude and orientation of the stress changes, as well as the local geology. This paper presents the monitoring results of gateroad response and support performance at two longwall mines at a 180-m and 600-m depth of *** the first mine, a three-entry gateroad layout was used. The second mine used a four-entry, yieldabutment-yield gateroad pillar system. Local ground deformation and support response were monitored at both sites. The monitoring period started during the development stage and continued during first panel retreat and up to second panel retreat. The two data sets were used to compare the response of the entries in two very different geotechnical settings and different gateroad layouts. The monitoring results were used to validate numerical models that simulate the loading conditions and entry response for these widely differing conditions. The validated models were used to compare the load path and ground response at the two mines. This paper demonstrates the potential for numerical models to assist mine engineers in optimizing longwall layouts and gateroad support systems.

关键词： Coal mining Longwall Gateroad Support Numerical models

Assessing support alternatives for longwall gateroads subject to changing stress

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International Journal of Mining Science and Technology 2021年第1期31卷 103-110页

作者： Gabriel S.Esterhuizen I.Berk Tulu Dave F.Gearhart heather dougherty Mark Van Dyke National Institute for Occupational Safety and Health Pittsburgh Mining Research DivisionPittsburghPA 15236USA West Virginia University MorgantownWV 26506USA

Longwall gateroad entries are subject to changing horizontal and vertical stress induced by redistribution of loads around the extracted *** stress changes can result in significant deformation of the entries that may include roof sag,rib dilation,and floor *** operators install different types of supports to control the ground response and maintain safe access and ventilation of the longwall *** paper describes recent research aimed at quantifying the effect of longwall-induced stress changes on ground stability and using the information to assess support *** research included monitoring of ground and support interaction at several operating longwall mines in the U.S.,analysis and calibration of numerical models that adequately represent the bedded rock mass,and observation of the support systems and their response to changes in *** models were then used to investigate the impact of geology and stress conditions on ground deformation and support response for various depths of cover and geologic *** research results were summarized in two regression equations that can be used to estimate the likely roof deformation and height of roof yield due to longwall-induced stress *** information is then used to assess the ability of support systems to maintain the stability of the *** application of the method is demonstrated with a retrospective analysis of the support performance at an operating longwall mine that experienced a headgate roof *** method is shown to produce realistic estimates of gateroad entry stability and support performance,allowing alternative support systems to be assessed during the design and planning stage of longwall operations.

关键词： Longwall Gateroad Support design Coal Standing support