Newly developed pressure adaptable concrete lining for high pressure hydraulic tunnels

Abstract

A pressure adaptable concrete lining (PACL) for hydraulic tunnels with high water pressure and high groundwater pressure was developed based on the thick-walled cylinder theory. One of the functions of the designed lining structure is that it can transfer the tunnel water pressure to the lining outer wall such that the lining bears compressive stress only. Moreover, the groundwater around the lining can be discharged so that the compressive stress in the lining caused by the groundwater pressure will be reduced during the tunnel emptying period. A test system of hydraulic tunnel lining with 3 m in diameter was developed to evaluate the effectiveness of the PACL. The filling and emptying process of tunnel water were simulated and the lining radial and hoop stress in two conditions were recorded and analyzed. Comparing with concrete lining (CL), the PACL can be kept compressed during the period of water filling. It may effectively take advantage of the high compressive strength of concrete and avoid lining cracking caused by high tensile stress. During the period of water emptying, the groundwater pressure acting on the outer wall of the PACL could also be decreased effectively, therefore the damage to the concrete due to the high groundwater pressure could be avoided. The results of this study show the effectiveness of the PACL in solving the issues caused by high tunnel water pressure and groundwater pressure in hydraulic tunnels and its wide application prospects.