| The generic term for forms of the earth's surface and underground which were formed by the water with corrosion strength carrying on soluble rock is the karst. How the karst influences hydroelectric projects relates to its scale and relative position to hydroelectric projects, which involves many aspects such as the safety of construction and operation period, project quality, construction progress and construction cost etc. Numerical simulation combing the project situation and mathematics model need to be carried on to analysize the impact of karst on stability of surrounding rock mass of underground caverns. And the measure to deal with the karst should be choosed by techno-economic comparison according to computation results, considering the project quality, progress, safety and cost etc..The W24 that disclosed pipelines and swallet wells nearby the powerhouses reaching above 15 strips, the spreaded horizontal length surpassing 420 meters, the whole length amounting to more than 1,000 meters and the elevation difference over 100 meters, constructs the biggest scale karst system at the Goupitan Hydropower Station underground powerhouse, and pass through entire large-scaled cavities which take the main generator room, the main transformer room and the tailrace surge room as represents.The paper described the growth and distribution of the W24 karst pipelines (caverns) in detail. Using three-dimensional Lagrange and the two-dimensional plane finite element numerical computational method, the paper analyzed influence of the W24 karst system on stability of surrounding rock mass of Goupitan Hydropower Station underground caverns. It is concluded that this influence is less, but this karst system can lead regional rock moving, plasticarea accretion and strain-stress condition worsening nearby the W24 karst pipes. Based on the above results, a plan is brought forward that backfill ranges is apart from in the upstream and downstream frontier walls of caverns contour interval 15 meters scopes, vault vertically stretching 20 meters. Through being analyzed and compared, it is considered that completing the concrete backfill construction before excavating the third layer of the main generator rooms can satisfy stability request of surrounding rock mass of the underground cavities. Combining security of the construction period and operation period, the concrete measures and advices of disposing caverns are also proposed. The whole study provides the theory basis for the design and the construction of Goupitan Hydropower Station underground power station caverns. Its research and the analysis methods have the model significance to other similar projects.
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