Analysis of Overlying Strata Movement Characteristics of Igneous Rock Roof Working Face Mining
With the increase of mining depth,there is igneous rock intrusion in some mining areas,forming hard and thick roof,which greatly increases the difficulty and danger of mining.Aiming at the prob-lem of strong rock pressure in the working face of igneous rock roof in a coal mine,the roof stress and failure characteristics in the mining process of igneous rock roof working face are studied by numerical simulation.The results show that the igneous rock roof plays a key role in a certain extent due to its large bearing capaci-ty,which makes the first weighting step of the working face larger,resulting in the roof stress concentration coefficient reaching 1.71 when the working face is first pressed,and the roof plastic zone expands rapidly.When the working face advances to a square,the igneous rock roof reaches the limit span,close to the ener-gy storage limit,and is in the limit stress state.The fracture of the igneous rock roof leads to the instanta-neous release of elastic energy,which is an important reason for inducing rock burst.After the working face is advanced to a square,because the igneous rock roof has been broken,the plastic zone continues to devel-op upward,and the failure mode of the fracture area is mainly tensile failure.According to the simulation,a reasonable roof cutting blasting area is determined.After the implementation of roof cutting pre-splitting blasting,through drilling and peeping,multiple vertical and horizontal cracks are generated inside the roof,especially the longitudinal cracks,and there is no punching phenomenon.The pressure relief effect is good and the cost is saved.
igneous rock roofoverlying strata movementvertical stressplastic zone
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