Optimised anchor-grouting support system for inclined composite roofs in deep coal mine roadways

Stabilising inclined composite roofs in coal mine roadways has long been a critical challenge in mining engineering. Traditional support systems often fail to prevent interlayer shear deformation, leading to cable shear failure, large roof deformations, and even collapse. To address these issues, this study proposes a spatially optimised anchor-grouting combined support system integrating space-interlaced anchoring and open grouting method for inclined composite roofs. Steel sleeves are configured on cables to improve the shear resistance. And a spatially sequential layout of variable-length cables is adopted, which enables anchoring into different rock strata to improve stress distribution. In addition, grouting capsules are employed to achieve efficient grouting and simplified construction without shotcreting. Through mechanical analysis and field implementation in a deep experimental roadway, the proposed support system is validated. Monitoring results show that the maximum roof displacement is reduced from 315 mm (traditional support) to below 105 mm (optimised support), and no cable shear failure occurs.