Comprehensive investigations of the strength and stability of workings of the powerhouse works of an underground hydroelectric station

The chamber workings of the powerhouse works (PHW) of the h y d r o e l e c t r i c s t a t i o n under c o n s i d e r a t i o n r e p r e s e n t a g e n e r a t o r room (58 m h igh , 19.5 m wide) and t r ans fo rmer room (15 m h igh , 13.5 m wide) . They a re in tended to house hydropower, power, and h y d r a u l i c equipment. The workings are located at a depth of 160 m from the surface and have a length of 280 m each. The distance along the axes of the underground generator and transformer rooms is 42.5 m. The total volume of rock excavation in these two workings is about 360,000 m s. The large size and importance of the structures impose high demands on a reliable estimation of their strength and stability. These problems were investigated on the basis of a combined method [i], including an engineering-geologic analysis of the construction conditions, static calculations, and experiments on models.