Modelling coal pillar stability from mine survey plans in a geographic information system

Abstract

An underground bord-and-pillar coal mine can, over a lifetime of a few decades, result in several tens of thousands of pillars being left behind in its abandoned workings. For South Africa, the total number of coal pillars in abandoned workings is estimated to be in the region of 6 million (van der Merwe and Mathey, 2013a).Currently, there are 98 cases known in which isolated but large groups of pillars have collapsed (van der Merwe and Mathey, 2013b). Consequently, large subsidence troughs occur on surface, potentially endangering infrastructure, housing, and ultimately lives. The prediction of long-term instabilities in underground workings therefore becomes imperative for regional development planning, and is also compulsory for mining companies in order to obtain mine closure certificates.The challenge in assessing pillar stabilityrelated risk is to take into account the great number of pillars, their individual dimensions, geometries, and deterioration over time. One can imagine that an unfavourable combination of these factors may cause localized areas of weakness in the underground panels. Those areas can eventually trigger a collapse, which subsequently may spread towards stronger regions within the same panel. Such examples have been discussed in the literature (Mathey, 2010(Mathey, , 2013Mathey and Schulte, 2011).It is apparent that an extensive risk assessment for abandoned mine sites is required that allows fast and detailed access to spatial information. Furthermore, the longterm stability of underground panels needs to be analysed in high resolution, i.e. on an individual pillar-by-pillar basis. In this paper the use of a geographic information system to address issue is proposed.The principal methodology underlying the pillar stability analysis is to pick up mining dimensions, geometries, and dates from the original survey plans and process the data in a quasi-3D digital mine model, making use of a geographic information system (GIS). Within this model, individual safety factors are determined for each pillar in the underground workings.Empirical equations are implemented to predict pillar scaling, giving the expected deterioration of pillar size over time. Thus a dynamic risk assessment for pillar-related stability problems is obtained. All static and dynamic, measured and inferred information related to a pillar is stored in a relational database.Finally, the analytical results are projected back onto maps in order to facilitate the use of stability-related information by mine personnel. Surface structures can be included on these maps, so as to provide a comprehensive and detailed basis for assessing the risk involved with abandoned Modelling coal pillar stability from mine survey plans in a geographic information system by M. Mathey A practical method for analysing the individual stability of large numbers of pillars in bord-and-pillar workings based on mine survey plans is outlined. The procedure aims at modelling pillar safety factors and failure probabilities under tributary area loading as...

Effect of confining pressure strength on the characteristics of energy evolution and fatigue fracture of the coal‐rock structural body

“…The elastic energy index W ET is the ratio of elastic energy to dissipated energy, reflecting the ability to accumulate and dissipate energy. 32,33 Figure 11 shows the variation curve of the elastic energy index. When the confining pressure is constant, the elastic energy index decreases with the increase of the height ratio from 1:3 to 3:1.…”

“…The elastic energy index W ET is the ratio of elastic energy to dissipated energy, reflecting the ability to accumulate and dissipate energy 32,33 …”

Characteristics of Roof Ground Subsidence While Applying a Continuous Excavation Continuous Backfill Method in Longwall Mining

“…Geological and mining parameters to calculate roof sinking amount in CECB [27,30]. According to the Equations (15) and (17) as well as the parameters listed in the Tables 1 and 2, the maximum loads on the coal pillars and the filling bodies could be estimated. Figure 9a reveals the maximum loads and the strengths of the coal pillar while using filling materials with different water-solid ratios.…”

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Analysis the Characteristic of Energy and Damage of Coal-Rock Composite Structure Under Cycle Loading

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