Study on deformation mechanism and roof pre-splitting control technology of gob-side entry in thick hard main roof full-mechanized longwall caving panel

This paper explores the deformation mechanism and control technology of roof pre-splitting for gob-side entries in hard roof full-mechanized longwall caving panel (LTCC). The investigation utilizes a comprehensive approach that integrates field monitoring, theoretical analysis, and numerical simulation. Theoretical analysis has illuminated the influence of the length of the lateral cantilever beam of the main roof (LCBM) above the roadway on the stability of the gob-side entry behind the panel. Numerical simulations have further revealed that the longer LCBM results in heightened vertical stress within the coal pillar, developed cracks around the roadway, and more pronounced damage to the roadway. Moreover, numerical simulations also demonstrate the potential of roof pre-splitting technology in optimizing the fracture position of the hard roof. This technology significantly reduces the length of the LCBM, thereby alleviating stress concentration in the coal pillars and integrated coal rib while minimizing the destruction of the gob-side entry. Therefore, this manuscript first proposes the use of roof pre-splitting technology to control roadway deformation, and automatically retain the entry within a hard roof LTCC panel. Field implementation has demonstrated that the proposed automatically retained entry by roof pre-splitting technology effectively reduces gob-side entry deformation and achieves automatically retained entry.