Abstract
Underground space is vulnerable to large deformation influenced by the abnormal stress induced by the bearing coal pillar. A numerical simulation model was established to determine the redistribution of the abnormal stress induced by the mining activities. The double-yield model, the strain softening model, the interface model, and the Mohr–Coulomb model were determined to simulate the gob compaction effect, the pillar strength reduction effect, the structure plane discontinuity effect, and the rock mechanical behavior, respectively. This numerical simulation model is reliable to predict the abnormal stress under the bearing coal pillar by the comparison of the abutment stress from this model and the existing theoretical model as well as the entry roof surface displacement from this model and the field measuring method. The results from the validated numerical model indicate that the abnormal stress including stress concentration coefficient, stress gradient, and lateral pressure coefficient will redistribute to another state that the stress concentration coefficient and stress gradient increase gradually and then decrease, and the lateral pressure coefficient decreases gradually, then increases, and finally decreases sharply with the approach of the mining working face. Their maximum increasing rates are calculated as 121.05%, 198.56%, and 236.82%, respectively. This predicted mining-induced redistribution of the abnormal stress is available for designing the underground entry layout in the determination of the entry position, determination of the driving operation time, mining disturbing range warning, and the prediction of the strengthening support area.
Highlights
Coal as one of the widely used energy resources in recent years will be used to accelerate the social development for a long time in the future
E precious achievements mainly concentrate on the stress distribution under the bearing coal pillar, which ignore the abnormal characteristics especially for the disturbing effect of the mining operation [4,5,6,7]. e CVISC rheological constitutive model was used to simulate the long-term creep behavior of the entry rock under bearing coal pillar and revealed that the stress concentration was not Advances in Civil Engineering large enough to damage this creep behavior rock under shallow-buried conditions [8]. e numerical simulation model with the Mohr–Coulomb criterion was used to reveal the distribution of the abutment stress around the mining working face near the bearing coal pillar and design the entry position for a special case [9]
Stress Concentration Coefficient. e mining-induced redistribution of the stress concentration coefficient presents typical differences at different positions in front of the mining working face (Figure 5). It increases gradually with the approach of the mining working face, and its peak reaches 3.43 increasing by 50.44% compared with the starting value 2.28 in the point below the bearing coal pillar when the distance to the mining working face is less than 80 m
Summary
Coal as one of the widely used energy resources in recent years will be used to accelerate the social development for a long time in the future. E numerical simulation model with the Mohr–Coulomb criterion was used to reveal the distribution of the abutment stress around the mining working face near the bearing coal pillar and design the entry position for a special case [9]. This achievement just concentrates on the mining operation in one thick coal seam, which did not consider the lithology difference, gob compaction effect, and the pillar strength reduction effect. This deviatoric stress ignores the volumetric strain of rock materials, which did not agree with the reality
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