Abstract: In view of the insufficient bearing capacity of the dam foundation during the heightening and expansion of a tailings pond, vibro-replacement gravel pile was used to strengthen the foundation to improve the bearing capacity of the dam foundation. According to the engineering geological conditions, the pile length, pile diameter, pile layout and pile spacing were determined. Vibro-replacement gravel piles were arranged in two areas, with a total of 297 piles; 11 pile bodies and 12 inter-pile soil detection points were selected to test the reinforcement effect. The results show that the gravel pile is dense and the construction quality meets the requirements. After treatment of soil between piles in zone I, it is in medium dense state, and the degree of compaction is obviously improved, and the average blow count is increased from 8.0 to 18.2. After the treatment of soil between piles in zone Ⅱ, the overall state is medium dense and partial state is slightly dense, the degree of compaction is obviously improved, the average blow count is increased from 8.0 to 15.6, and the characteristic values of bearing capacity of foundation soil in zone I and zone Ⅱ meet the design requirements.