Pressure tunnel in the Urugua-i dam (Misiones, Argentina)

This paper includes, in a synthetic manner, the experience acquired from the design and subsequent loading operation of the pressure tunnel in the Urugua-i hydro-development, with scarce rock overburden on the lower section. This is a description of the approach used to check, in an economic and rapid manner, that at least within the range of pressures tested, the hydrofracturation phenomenom exists. The design of the lining is centered on satisfying the requirements of durability and control of water flow, related to the technology of the material used and the surrounding rock mass. Reference is made to the behaviour after the first pressure tests and the influence on the drainage system of the rock mass, which provide interesting orientative data, since the lower section of the tunnel is a media not free from the risk of hydrofracturation, although structurally significant for the resistance to internal pressures.