Meitan xuebao (May 2023)
Shock failure mechanism of roadway in extra thick coal seam and full anchor cable support technology
Abstract
In view of the serious shock failure of roadway in extra thick coal seam, based on elastic mechanics and shock dynamics, this paper studies the shock failure mechanism of roadway in extra-thick coal seam, reveals the main influencing factors of roof coal failure, analyzes the propagation process of dynamic load stress wave and the dynamic response characteristics of roadway surrounding rock and support system, and determines the effective anti-impact support technology of roadway surrounding rock in extra thick coal seam. It is found that the impact damage degree of the roadway roof is directly proportional to the static concentrated stress, the intensity of the shock source and the length of the roof coal rock beam, and inversely proportional to the propagation distance of the stress wave, the thickness and strength of the roof coal rock beam. The stress wave propagation process under shock dynamic load can be divided into stress initial vibration period, stress fluctuation period and stress adjustment period. During the stress initial vibration period, the particles on the surrounding rock surface of the roadway begin to vibrate, the pretension of the anchor cables is reduced. During the stress fluctuation period, the surrounding rock of the roadway becomes more damaged, the anchor cable appears to be damaged. During the stress adjustment period, the surrounding rock of the roadway tends to be stable, and the axial force of the anchor cable also tends to be stable. With the increase of shock dynamic load strength, the particle vibration velocity, displacement increment and acceleration of surrounding rock increase exponentially. The critical shock energy of roadway surrounding rock is 105 J, above which the damage to the roadway surrounding rock and anchor cable is aggravated. By adopting the full anchor cable multi-length yielding support technology, the roadway can form a shallow deep anchor high prestress layer and a deep multi-length yielding support layer, which can enhance the strength and thickness of the roof coal rock beam, reduce the dynamic load damage value of the anchor cable, and improve the impact resistance of the roadway surrounding rock. The engineering application shows that the development depth of cracks in the surrounding rock of the roadway is reduced by 50.47%−55.42%, the deformation is reduced by 52.89%−68.78%, the damage value of the anchor cable is reduced, and the stability of the surrounding rock of the roadway is significantly improved by using the full anchor cable multi-length yielding support technology.
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