Lessons From Compared Design of Underground Power Houses and Storage Rock Caverns

Lessons From Compared Design of Underground Power Houses and Storage Rock Caverns

Underground power houses of hydropower plants and caverns for storage of oil, gas or other substances are often considered similar, although quite important differences exist both in design and construction. By comparing their design and construction methods

the authors (each one a specialist in each type of cavern) intend to provide guidelines to designers of future large caverns, now being contemplated also for different other purposes, like waste storage, nuclear power plants, etc. The design methodology to be applied for both types of cavern is presented and compared, with focus on the most critical items, groundwater control, determination of rock mass properties and associated support to be placed. This, in our knowledge unprecedented, direct comparison between two different design methodologies proved to be quite worthy. The main outcome is that selection of location, characteristics and design of any type of cavern closely depends upon the final requirements for its use.Hydroelectric power houses and crude oil storage cavities are the two major types of large underground caverns. This paper exposes the deep differences that actually exist between the two types of cavern, despite their similarity in shape. Requirements dictated by the unlike conditions of future operation of each type of cavern directly influence methodologies for design, construction and maintenance.The cavern geometry will have to cope with the geological conditions and other external constraints such as the in-situ stress regime. But it shall also suit the final utilisation to be made of the cavern.Underground power houses shall provide the necessary volume suitable for turbines installation and maintenance. The geometry mainly depends upon the type, number and size of turbines. Often, smaller caverns of non-negligible size are excavated nearby, such as a transformer cavern or a downstream surge chamber (where water level is to vary rapidly during transient conditions). All different caverns of an underground hydroelectric power plant will be referred in the following to the "power house complex". The final arrangement is often a compromise between civil engineers, hydromechanical and electrical engineers.

2016-08-29

Vibert, C.

Vaskou, P.

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