Criteria of Rock Bursts for Longwall Muting

Zorychta, A.; ElECZEK, Z.; Cyrul, T.

doi:10.1016/b978-0-08-035894-9.50093-7

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“…The underlying assumption made at the stage of model development was that rock strata surrounding the face entry should exhibit the equivalent bending rigidity taking into account the floor and main roof parameters. Old excavations were treated as a linearly deformable medium, the coal seam viewed as a nonlinearly deformable medium, its stress-strain characteristics approximated by straight line sections in accordance with the energy equivalence criteria (Zorychta et al, 1986;Mróz & Nawrocki, 1989;Baryakh & Gegin, 1997;Lin'kov, 2001). The equivalent roof deflection was assumed to be induced by the bending moment whilst the working zone interactions were governed by normalised values of the powered support capacity.…”

Section: Conceptual and Theoretical Backgrounds Of The Stress State D...mentioning

confidence: 99%

Archives of Mining Sciences

Chlebowski

Burtan

Zorychta

2018

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Recalling the body of experience gathered in the collieries of the Upper Silesian Coal Basin, the increased risk of seismicity and rockburst occurrences in confined conditions including the exploitation of remnants were identified. This study investigates geomechanical aspects of longwall mining in the areas affected by old excavations aimed at relaxation of a multi-bed deposits within a thick coal seam or a group of seams. It is assumed that high-energy seismicity is another factor determining the rockburst hazard alongside the state of stress. A case study is recalled, describing a colliery where mining-induced seismic activity of a de-stressed coal seam remained at the level comparable to or higher than it was experienced in the de-stressed seam operations. An analytical model was used to study the stress state and potential loss of structural continuity of an undisturbed rock body surrounding the longwall panel being mined beneath or over the abandoned workings. Recalling the developed model of the system involving nonlinear functions demonstrating the existence of abandoned mine workings within the rock strata, computer simulations were performed to evaluate the rockburst hazards along the face area. Discussions of results are based on observations of immediate roof convergence and the vertical stress concentration factor at the longwall face zone. Computational data of the modelled mining situations demonstrates that despite using the de-stressing method of mining, the occurrence of events impacting on mine working beneath and over abandoned workings cannot be precluded. Here the scale of rockburst hazards is determined by local mining and geological conditions, such as the type and extent of abandoned workings, their age and vertical distance between them and the coal seam currently mined.

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Section: Conceptual and Theoretical Backgrounds Of The Stress State D...mentioning

confidence: 99%