Abstract: The underground pump station for the water replenishing project from Niulan River to Dianchi lake in Yunnan Province is located in strong karst area, with large-scale karst carves, funnels and underground rivers exposed on the surface as well as underground river pipeline, karst caves and strong dissolution belt developed underground. To avoid the karst development zone and take effective measures to solve the karst water burst and collapse is one of the technical problems in the construction. By analyzing the karst features and development regularities, we adopted three measures for the construction (1) the long-span underground main power house is built in weak karst area to avoid underground river and strong corroded groove, and the bottom boundary of anti-seepage curtain for the underground main power house is determined 10-20m below the 1 695m elevation of micro-karst area; (2) forepoling is employed for large strong karst area before the excavation of underground caverns; (3) areas of safety monitoring for the power house’s operation are decided.

Key words: underground pump station, karst problem, forepoling, seepage-proofing bottom boundary, safety monitoring