ABSTRACT
The Westerscheldetunnel is a twin tube TBM road tunnel built from 1997-2003. The segmented lining consists of seven segments and a keystone. The rings are interconnected with cams and pockets. The original design used Kaubit strips to evenly distribute jack forces, but during execution the Kaubit was replaced by plywood. During execution of repair works because of a leakage, a severe crack, locally measured at 10 mm width, was found behind the fireproof shotcrete layer, in the crown of the tunnel. Further inspection revealed a 30 m long zone with cracks directly before the connection to the reception shaft. The tunnel operator organisation started a program to analyze the causes of the damage, to monitor the development and to design repair measures. Based on inspections and analyses, a possible cause is a combination of a stiffer ring connection than originally designed, a concentrated soil load from a stiff soil improvement above the crown, an economical reinforcement design and cyclic loading from temperature and tide. A structural repair measure inside the tunnel proved the most effective. Attention has been paid to the need for as little disturbance of availability for traffic as possible. The paper gives an overview of the analysis program, the damage hypothesis, the design of the repair measures and the status of the execution.
