Transfer of anchoring load in layered roadway roof under different lithological sequences

• DOI: 10.1007/s12517-018-4163-5
• Publication Date: 2018-12-27T10:25:19Z
• Authors: Zenghui Zhao; Wei Sun; Shaojie Chen; Qing Ma; Xiaojie Gao; Mingzhong Zhang
• Keywords: 0211 other engineering and technologies; 02 engineering and technology

Roadway roofs of coal measures strata mainly occur in layered structures. Due to high frequency of shearing or bending failures of rockbolt induced by layer separation or interlayer sliding of roadway roofs during the tunneling process, this study presents an intensive analysis of load distributions of rockbolts in layered roofs under different lithological sequences based on numerical simulations. First, numerical simulation models of cross-layer anchoring roofs of four different lithologic sequences (including hard-hard, soft-hard, hard-soft, and soft-soft) with effects of bedding planes taken into consideration were established. Then, the distributions of axial forces, shear forces, and shear stresses on rockbolts in different locations in each model were investigated. Finally, loading mechanisms and failure modes of rockbolts in layered roofs of different lithological sequences were elaborated based on the results of finite element analysis. Results indicate that cross-layer rockbolt is easy to produce combined deformation of tension and bending near the bedding plane. In this area, three internal forces of axial force, shear force, and bending moment exit on the cross-sections of rockbolt, meaning that the rockbolt is in a complicated stress state. In this case, the lithological sequence, thickness, and stress level of soft strata, as well as location of the bedding plane, have a significant effect on tension-bending failure of rockbolt.