The influence of the combined action of powerhouse and dam on sliding stability of gravity dam is a key problem in hydropower projects. In this paper

the problem is analyzed and discussed by means of application of elastic-plastic FEM and calculation of sliding stability safety factor of dam foundation in Jin’an qiao Hydropower Project. The results show that the combined action of powerhouse and dam could effectively improve the sliding stability of superficial dam foundation

but not helpful to the deep dam foundation of Jin’an qiao hydropower station riverbed dam section with the traditional method

overload method and safety factor of strength reserve . Moreover

under the combined action of powerhouse and dam

the maximal compression and tension stress in dam body are decreased effectively to make the stress distribution more uniform. At the same time

the deflection curve of power penstock becomes more smooth to decrease the additional stress caused by the deflection break

which is so as to benefit safe operation of the penstocks.