Pipe piles and split-cables: reinforcing weak mine pits

To mitigate the instability problem of heavy equipment foundations in deep coal mine chambers under high geo-stress, this study proposes a combined reinforcement strategy for foundation pits, which are mainly composed of pipe piles and split-level vertical cables. The weak rock mass around the pit is reinforced using combined cables and grouting. The split-level-arranged cables with different lengths improve the tensional strength of the rock mass, whereas the pipe pile at the pit corner can enhance the shear strength. The overall performance of the structure in terms of bearing capacity can be significantly enhanced by pouring pipe piles to integrate them and the pump foundation to form a cohesive structure. Both the foundation integrity and foundation pit strength can be improved by stepwise support technology. Finally, an improved reinforcement strategy is implemented in a deep-pump chamber in the Huainan mining area. The monitoring results indicate that the foundation pit stability was successfully controlled and floor cracking and tilting of the pump foundation were avoided by using the improved support method.