| Tunnels that have suffered severe damage from earthquakes, ground swelling or ground squeezing can be repairedby installing an additional concrete lining according to the degree of their damage. However, the design of the additional lining isbased on an empirical approach that does not consider the remaining strength of the original permanent lining. To solve theproblem, two series of laboratory loading tests were performed. The first series consisted of continuous loading on both thedamaged permanent lining and a new additional concrete lining to simulate the swelling or squeezing of the ground. The secondseries entailed loading and unloading of the permanent lining, installing the additional lining after that, and then re-loading bothlinings to simulate earthquake conditions. The results indicated that the damaged permanent lining had a remaining strength thatwas effective in load-bearing capacity in combination with the additional lining, depending on the degree of the damage of thepermanent lining. Also, the total load-bearing capacity of the two linings was greater than that of each independent concrete lining,even in the case when the permanent lining was significantly damaged. These results aid in the rational design of an additionallining by considering the remaining load-bearing capacity of the already-damaged permanent lining. |
