Coal pillar strength estimation from failed and stable cases

Sheorey, P.R.; Das, M.N.; Barat, D.; Prasad, Reshma; Singh, B.

doi:10.1016/0148-9062(87)92256-x

Cited by 64 publications

(12 citation statements)

References 3 publications

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“…A unique approach to pillar design at depth was pursued by Sheorey et al (1987) in India, in that a strength formula was proposed that accounts for the influence of virgin stress conditions on the load-bearing capacity of the pillar. The fundamental assumption behind coal pillar strength at depth was that a pillar may be able to retain some of the original horizontal confining stress existing in the coal prior to excavation, depending on its width-to-height ratio and its contact conditions with the surrounding strata.…”

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confidence: 99%

Critique of the South African squat coal pillar strength formula

Mathey

Merwe

2016

J. S. Afr. Inst. Min. Metall.

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The South African squat coal pillar strength formula, developed by researchers from the Chamber of Mines Research Organization in the 1980s, predicts an exponential increase in coal pillar strength once a critical width-to-height ratio of 5 is exceeded. The arguments that have been proposed in favour of this formula are discussed critically in this paper.Field experience with squat pillars in the USA and evidence from published physical, analytical, and numerical model pillar studies corroborate the fact that a squat effect is unlikely to occur in coal pillars at width-to-height ratios less than 10. Furthermore, an exponential increase in peak strength of coal pillars does not exist. An alternative design criterion for squat pillars in South Africa is therefore suggested. squat pillars, coal pillar strength, bord-and-pillar mining.

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confidence: 99%

Critique of the South African squat coal pillar strength formula

Mathey

Merwe

2016

J. S. Afr. Inst. Min. Metall.

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“…A century ago in the United States, the design of coal pillar dimensions depended heavily on intuition or established rules of thumb [12]. However, currently, various coal pillar design guidelines have been developed on the basis of indoor tests and theoretical analyses [13][14][15][16]. Sheorey et al [13] analysed 23 cases of pillar instability and 20 cases of safe and stable pillars and proposed a new pillar strength equation for practical values of the width-to-height ratio.…”

Section: Introductionmentioning

confidence: 99%

Width Design of Small Coal Pillar of Gob‐Side Entry Driving in Soft Rock Working Face and Its Application of Zaoquan Coal Mine

Ai¹

2021

Advances in Civil Engineering

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Reasonable width of gob-side coal pillar can reduce the waste of coal resources and is conducive to roadway stability. According to the distribution of internal and external stress fields at the working face, a method for determining the width of gob-side coal pillar was proposed. The coal pillar and roadway should be set within the internal stress field, and support is provided through the anchored part and the intact part of the coal pillar. The method was used in the design of the coal pillar at No. 130205 working face of Zaoquan Coal Mine. The calculation results indicated that the width of a coal pillar suitable for gob-side entry is 6.0 m. It is reasonable to arrange the roadway and coal pillar in the low-stress zone with a width of 11 m. During tunnelling of roadway and stoping of the working face, the deformation of the roadway increased with a reduction in the distance from the working face. Even during stoping of the working face, there was an approximately 1.5 m intact zone in the coal pillar. This indicates that the proposed method of designing small coal pillar of gob-side entry driving is reliable.

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“…Martin 20 carried out pillar case studies, and found that the pillar strength is directly related to the pillar width-to-height ratio. Sheorey 21 improved the calculation formula of coal pillar strength by introducing buried depth and width-to-height ratio. Ebrahim 22 reported that weathering and moisture greatly reduce the strength of coal pillars.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on granite acoustic emission and micro-fracture behavior with combined compression and shear loading: phenomenon and mechanism

Cao

Chen

et al. 2020

Sci Rep

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One element that is essential to consider in underground mining engineering applications is the possibility of pillar failure, which can result in deadly geological disasters, including earthquakes and surface subsidence. Pillars are commonly present under an inclined state and are significantly dependent upon combined compression and shear loading. However, many scholars regard the pure uniaxial compression strength (UCS) of rock as the main evaluation index of pillar strength, which is inconsistent with the field practice. Hence, the present study developed a novel combined compression and shear test (C-CAST) system, which was applied in the investigative acoustic emission (AE) experiments to characterize the failure mechanism and micro-fracture behavior of granite specimens at different inclination angles. The experimental results presented the exponential decrease of UCS of inclined specimens with increase in the shear stress component. Changes in the inclination angle with a range of 0°–10° produced a splitting-shear failure fracture mode from the initial splitting failure. In comparison, an increase in the inclination angle from 10° to 20° produced a single shear failure fracture mode from the initial combined splitting-shear failure. The specimens exhibited nonlinearly reduced microcrack initiation (CI) and damage (CD) thresholds following an increase in the inclination angle, suggesting the dependence of the microcrack initiation and propagation on the shear stress component. The ratio of CI and CD thresholds to inclined UCS varies within a certain range, indicating that the ratio may be an inherent property of granite specimens and is not affected by external load conditions. Additionally, the rock fracture behavior was largely dependent upon the mechanism of shear stress component, as validated by the microcrack initiation and growth. Finally, a modified empirical formula for pillar strength is proposed to investigate the actual strength of inclined pillar. Results of a case study show that the modified formula can be better used to evaluate the stability of inclined pillars.

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Coal pillar strength estimation from failed and stable cases

Cited by 64 publications

References 3 publications

Critique of the South African squat coal pillar strength formula

Critique of the South African squat coal pillar strength formula

Width Design of Small Coal Pillar of Gob‐Side Entry Driving in Soft Rock Working Face and Its Application of Zaoquan Coal Mine

Experimental study on granite acoustic emission and micro-fracture behavior with combined compression and shear loading: phenomenon and mechanism

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