Principle and engineering application of "bolt-U typed steel support-filling" synergetic control for deep rockburst roadways

To address the challenge of managing surrounding rock deformation in deep rockburst roadways, this study utilizes the 402101 working face of a coal mine as the engineering background. Through a combination of field investigation, theoretical analyses, numerical simulations and industrial tests, the instability characteristics of the roadway, identifies the primary controlling factors was examined, and the stress transfer mechanisms under static-dynamic loading conditions was elucidated. A novel "bolt-U typed steel support-filling (BUF)" synergetic control technology is proposed and subsequently validated through practical engineering applications. The results show that the principal factors contributing to surrounding rock instability include the interaction of high static-dynamic loads, the inadequate impact resistance of support materials and the poor synergy within the support system. The BUF system establishes a composite bearing structure by employing pre-stressed anchor cables (to control crack propagation), the yielding of U-typed steel supports (to facilitate energy conversion), and the uniform energy dissipation provided by the filling layer. In accordance with the theory of surrounding rock structure stratification, the surrounding rock of the roadway is categorized into three layers: the support layer, the anchoring layer and the original rock layer. The compressive stress of the support layer is influenced by the rockburst failure coefficient k_b, the dimensions of the roadway, the physical properties of the surrounding rock and the support resistance provided by bolts and cables. An impact risk assessment methodology is developed, focusing on the relationship between the compressive stress and the strength of the support layer. Computational examples reveal that the BUF system can decrease the compressive stress of the support layer by 18.5% to 42.1% and withstand dynamic load disturbances at k_b=2.0. Numerical simulation results indicate that in comparison to conventional support systems, the BUF system reduces the plastic zone by 79.1%, decreases the displacement of the roof and sidewalls by nearly 90%, fully activates the passive bearing capacity of the supports, and optimizes the energy field distribution. In practical engineering applications, the maximum displacement of the surrounding rock controlled by the BUF system is 43 mm, and the maximum stress on the supports is 0.34 MPa. The structure remains stable, thereby effectively ensuring safe and efficient mining operations.