Received 18 July 2011 The design of Three Gorges Hydropower Station Zhou Shuda, Xie Hongbing (Changjiang Institute of Survey, Planning, Design and Research, Changjiang Water Resources Commission, Wuhan 430010, China ) Abstract:Using physical model and numerical simulation techniques, some technical problems were studied systemati- cally, including layout of power station, measures of sediment and floating debris discharging, types of intake, embed- ded types of spiral case, layout of underground powerhouse tunnel group and block reinforcement.It was optimal in technique and economy with the arrangement of powerhouse at the dam- toe of both banks +underground powerhouse in the right bank, as well as the intake with a single and small orifice. The sediment and debris problems could be solved with disperse sediment ejection and floating debris discharging holes. With the adoption of techniques for spiral cases such as heat and pressure preservation, cushion layer and combined embedding, the stable operation of generating units can be guaranteed. The arrangement of tailrace tunnel with sloping ceiling was better than that of tailrace surge tank. The technical requirements related to the embedding type of spiral case were proposed. The reinforcement of huge unfa- vorable blocks was discussed and the new idea for block reinforcement using anti- sliding piles and normal compressive stress of structural plane was put forward. Key words: Three Gorges Power Station; layout; sediment and floating debris discharging; spiral case embedding; shallow embedment; block reinforcement 1 Introduction The general layout of Three Gorges Project ( TGP) is as follow: flood discharge dam monolith in the middle of river bed, powerhouse at dam- toe and powerhouse monolith on two sides of the river channel , ship lift and ship lock on the left bank, and underground powerhouse in the right bank.The powerhouse structure is one of the three biggest structures of the Three Gorges Project , and is equipped with 32 turbine generator units with a unit capacity of 700 MW and a total capacity of 22 400 MW. It is the biggest hydropower station in the world with annual utilization hours of installing capac - ity of about 4 000 h and average annual energy out - put of 880×10 8 kW· h. Its construction has obvious significance for increasing clean energy proportion and promoting social and economic development for China . 2 General layout of power station structure At the dam site of TGP, the river valley is open, and the river bed and overbank can meet the layout re- quirements of flood discharge monolith, powerhouse monolith and powerhouse at dam- toe.The bedrock of the constructions is complete and strong, which is favor- able to dam construction.In the demonstration stage , comparison of 3 general layout schemes of power station structures was researched: namely, powerhouse at dam- toe at two banks +underground powerhouse in the right bank; powerhouse at dam- toe of the left bank, overflow powerhouse and underground powerhouse in the right bank; powerhouse at dam- toe of the left bank + two- row powerhouse of the right bank. For the 3 schemes, comprehensive technical and economic comparison was conducted in aspects of lay- out coordination, flood discharge safety , staged con- struction condition, powerhouse complexity , construc- tion difficulty , operation condition, construction period and investment.Finally the scheme of powerhouse at dam- toe of two banks + underground powerhouse in the right bank was adopted ( Fig. 1). 1) Power station at dam- toe. The powerhouse struc- ture of the two banks consists of dam- type intake, pres- sure penstock, main powerhouse, upstream and down- stream auxiliary powerhouses, tail channel and front area of the plant.14 generators units are installed in the left power station with dimension of 634. 7 m ×68 m ( upper part 39 m)×94. 3 m ( length ×width × height ); corre- spondingly, 12 generator units are installed in the right power station with dimension of 567. 1 m ×68 m ( upper part 39 m) ×94. 3 m ( length × width × height ). The 6 6 Engineering Sciences