Verification of the performance of the precast concrete lining in the Diabolo Tunnel and Liefkenshoek Rail Tunnel

During construction of the Diabolo tunnel and the Liefkenshoek railway tunnel in Belgium, strains were monitored in several cross-sections of the precast concrete segmental lining. The obtained measurement data allow evaluating the in situ behaviour of the concrete lining under numerous loading conditions during and after tunnel drive works. The gradual development of strains in the initial stage after ring erection is discussed in relation to the grout loading, hydraulic jack forces and transferred soil and water pressures. Measurement sections below the River Scheldt show that the water level variation, linked to the tides of the North Sea, is clearly depicted in the strain results as a half-daily fluctuation. Results show that despite the rough site conditions, strain monitoring proves a useful verification of tunnel lining performance and an important addition to tunnel design practice.