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Abstract The proposed hydropower station which is located on lower reaches of Jinsha River is characterized by the large scale and complex arrangement. The height of cylindrical throttled surge chamber is about 100 m，and the diameter reaches 50 m. The stability and supporting measures of chamber arch are the noteworthy factors needed to be considered. In order to analyze potential stress-type failure，deformation and collapse caused by structure planes of tailrace surge chamber arch crowns under complex geological conditions，engineering geological analysis and three-dimensional numerical simulation(3DEC) are adopted to study the stress concentration arrange，stress concentration degree and risk of high stress failure，and the effects of interlayer fault zones on stability of surrounding rock are demonstrated. The results show that the overall stability of cavern satisfies the engineering requirements，and the relatively stress concentration degree(30–44 MPa) of arch crown doesn?t cause prominent issue of high stress failure. However，bedding fault zones reduce the stability of surrounding rock distinctly，thus large sliding deformation occurred along the bedding fault zones and shear yield occurred in NNE direction from surface to 7 m superficial zone. After strengthened reinforcements including system supporting and concrete replace are adopted，sliding deformation of bedding fault zones is reduce obviously，and interlaminar band security reserve is improved.
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Received: 12 April 2012
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2012, Vol. 31 
