Study on interval rupture mechanism and support optimization of layered roof

Abstract

In view of the practical engineering problem that the layered roof of deep roadway is easy to deform and destroy but difficult to support, the mechanical model of deformation and failure of roof rock beam under the combined action of vertical stratum load and horizontal load is established by using the theory of material mechanics and structural mechanics. The analytical solution of internal force at the end and midspan of rock beam and the extreme stress at the upper and lower edges of rock beam midspan are discussed. Based on the equivalent calculation model of physical and mechanical parameters of layered roof, the failure criterion of layered roof is proposed. According to the static equilibrium equation of the rock beam in the horizontal direction, the position of the stress neutral layer and the height of the tensile region of the rock beam under the conditions of fixed support and simple support are analyzed. The results show that the tensile zone height of rock beam is positively correlated with vertical stratum load and horizontal lateral pressure, and negatively correlated with elastic modulus and thickness-span ratio of rock beam. Under the same span condition, when the fixed rock beam is transformed into a simply supported rock beam, the stress neutral layer will move down and the height of the tensile region will decrease. However, after the instability of the rock mass in the roadway sidewall leads to the increase of the effective span, the stress neutral layer of the roof rock beam will move up and the height of the tensile region will increase. Based on the neutral layer distribution characteristics of layered roof and self-stable invisible arch theory, the invisible equilibrium arch distribution law of each rock beam in layered roof is analyzed. Finally, the rationality of the above view is verified by an example of a working face.