Long-term mechanical and hydraulic interaction and leakage evaluation of segmented tunnels

With regard to tunnel design, the presence of water requires that consideration be given to leakage from and pore water pressure on the lining. A segmented tunnel is generally constructed as a watertight tunnel with a certain amount of allowable leakage. It has been reported that the leakage from watertight tunnels increases with time due to lining deterioration. The deterioration of joints and/or grouts in segmented linings changes the hydraulic boundary conditions, which results in long-term hydraulic and mechanical interaction, and consequently, an increase in leakage. In this paper, the coupled mechanical and hydraulic interaction between the segment lining and the surrounding ground is investigated using the numerical modeling method. It is identified that hydraulic deterioration causes significant changes in pore water pressure and structural behavior, and accelerates leakage. It is shown that design requirements for joint contact pressure are not sufficient for controlling long-term leakage, as they do not consider hydraulic deterioration. A strain requirement, controlling leakage, and a leakage evaluation method, considering hydraulic deterioration, are proposed in this paper.