Design criteria for plain concrete lining in water and power tunnels

Abstract Plain concrete lining is used in the construction of many power tunnels in rock masses having good and fair qualities under internal pressure ( p ). This type of concrete is susceptible to cracking and jointing as a result of the construction process. The average crack opening ( 2u ) is estimated to be approximately equal to (1 + ν) t(f t + p)/E , where E and ν are the modulus of deformation and Poisson's ratio of rock mass, respectively; and t and f t are, respectively, the thickness and ultimate tensile strength of the concrete lining. In order to ensure that the crack will close over time, this opening ( 2u ) should not be allowed to exceed a permissible limit. Case histories are included to obtain the permissible limits for crack opening and spacing.