Abstract:The mined-out areas of a metallic mine, complemented by karst caves, made the construction of the pile foundations of a bridge above very difficult and resulted in poor piles. To ensure file construction quality, it was proposed to inject concrete into the mined-out areas and the karst caves in question, and to use steel sleeve pipes to ensure the quality of foundation bore holes. After these measures were taken, foundation quality tests showed that all the piles were of Class I, hence very successful. This attempt thus brings useful experience to operations under similar circumstance.