| 摘要 |
PURPOSE:To reduce a construction cost, by a method wherein cavities, communicated to the open air, are bored in bedrock facing a reservoir in a manner to be positioned between the maximum water level and the minimum water level of the availlable water depth of the reservoir, and water in the reservoir is introduced to the cavity through a head-race through which a water level in the reservoir is lowered to a lower most value. CONSTITUTION:Plural cavities 4, each having a bottom located in a level eqal to a lowermost water level of an available depth (h) of a reservoir 2, a height eqal to or slightly higher than the water dept (h), and communicated with the open air through a ventilating hole 8, are formed in partallel to each other in bedrock 3 facing a reservoir 2 up a flow from a dam 1. Water in the reservoir 2 is introduced to each cavity 4 through a headrace 5 having a bottom located in the same level as the lowermost water level of a water depth (h). The headrace 5 is shut off by a regulating gate 6, where necessary, and sand accumulated in the cavity 4 is discharged through a sand discharge vertical shaft 7. |
