Underground Powerhouse Design And Wall Rock Stability Analysis Of Jiangkou Power Station

Jiang Kou power station is an engineering of comprehensive utilization and its main function is electric power supplyment.lt is the lowest level of exploring Lotus River. The location is 130km from urban area of ChongQing. The basin area controlled by dam site is 794 km2, long time average annual flow is 152m3/s, the normal runoff is 4,790,000,000 m3, the normal level of reservoir is 300m, the gross capacity of reservoir is 497,000,000 m3, installed capacity of hydropower plant is 300MW.The pivot belongs to the 2nd level engineering, and power generation of the first set was completed in December, 2002, which of the third set was in October, 2003.The underground powerhouse of JiangKou is composed of main house, auxiliary plant, omnibus bar hole, switch house of main transformer, high tension cable room, outgoing line well, mucking hole(aeration hole),traffic hole, unwatering gallery.The length of main house and auxiliary plant is 103.25m,the width is 19.20m, the height is 51.20m.Three sets of 100MW turbine generator are arranged in plant. There are three high pressure diversion bypass whose inside diameter is 5.6m in the upriver side wall of main house, which come into powerhouse and vertical to the axes of powerhouse. The space between three diversion bypass of high pressure is 17.50m. There are three tail branch pipes whose inside diameter is 5.02m in the downstream wall, which water out forward. The setting depth of underground powerhouse is 120m under ground in the body of ash rock and dolostone. All the grottoes located in the body of geologic structure which is short of crack and alteration.The main transformer cave room located in the downstream of main powerhouse. The parallel distance is 28m between main powerhouse and main transformer cave room. The length of switch house of main transformer is 72.20m, the width is 14.20m, the height is 25.60m. The height of outgoing linewell whose internal diameter is 9m ,is 113.50m, The well is connected with 220kV outgoing line field on the ground.There are three omnibus bar cave on the elevation of 186.95m between main power house and main transformer cave, whose section is 5.90m 6.75m. The distance between sketch of gate hole is 17.50m. The omnibus bar of each set is connected with main transformer through its omnibus bar cave. There is mucking hole as well as aeration hole on the right side of the two parallel cave room, whose section is 8 X 6.5m.There are two ply unwatering galleries whose section is 2.5 X 3m ,about 10m from side wall of the two cave rooms.The paper involves design principles and design keynote from the view of engineering in conjunction with Jiang Kou powerhouse. The author puts forward opinion on adoption of harnessing method of powerhouse, distinctive feature of arrangement of underground cavities, stability analysis of wall rock, choice of timbering method, and design method of runaway girder. The opinion and conclusion of the paper can be applied in other design of underground powerhouse.