Support technology for weakly cemented roof roadways under alkaline water infiltration

Alkaline water infiltration accelerates the softening of weakly cemented surrounding rock and degrades the anchorage performance of support members, thereby promoting roof separation and persistent roadway deformation. Taking the north-wing transportation roadway of the No. 7 coal seam in Dananhu No. 7 Coal Mine, Xinjiang, as a case study, this study proposes a staged control strategy consisting of strengthened primary support, dynamic monitoring, and secondary reinforcement. Numerical simulation, field monitoring, and cable pull-out tests were conducted to evaluate surrounding-rock deformation, roof-separation evolution, and anchorage performance under the original, optimized primary, and reinforced support conditions. Under the original support system, roadway deformation was dominated by roof subsidence, shallow roof separation was more pronounced than deep separation, and cable anchorage capacity deteriorated under water infiltration. Strengthened primary support substantially reduced roadway deformation and limited the development of the plastic zone. Secondary reinforcement effectively restrained incremental deformation in unstable sections and confined the further development of roof separation mainly to the shallow zone. Cable pull-out tests confirmed that the optimized support schemes maintained the anchorage capacity required for roadway stability. These results demonstrate that the proposed staged strategy provides a practical approach for the long-term stability control of weakly cemented roadways subjected to alkaline water infiltration.