Computational Analysis of Cyclic Fracture of Elastic Foundation Beam Under the Multifactor Effect

This study established a mechanical model of an elastic foundation beam for hard roofs in stopes, considering the support rigidity system in the cyclic fracture movement of basic roofs. The characteristic functions of the deflection and bending moment of a three-section hard roof (front of rock beam wall, roof controlling zone, and cantilever zone) were obtained. The action rules of failure characteristics and coal body elasticity modulus k(c) of the hard roof, rigidity k(s) of the support system in the roof controlling zone, elasticity modulus E of the basic roof, and roof load q on the roof fracture and coal wall deformation were explored. Results were shown that: the end fracture of cyclic rock beam movement occurred in front of the coal wall. With the k(c) value decreased, the maximum bending moment of rock beam moved toward the deep part of the coal body. The larger the k(s), the lower the maximum bending moment of the rock beam, and the lower the vertical displacement of the coal body and the deformation of the hydraulic support. When the E increased, the maximum bending moment value of the rock beam and the lead of the peak position of bending moment increased, and the vertical displacement of the coal body at the coal wall decreased significantly. E only influenced the change rate of the subsidence curve of the rock beam within a certain range at the rear portion of the coal wall. The maximum bending moment of rock beam and the vertical displacement of coal body at the coal wall increased proportionally as the load q increased.