Photogrammetric Record 1 Published as: Nuttens, T., Stal, C., De Backer, H., Schotte, K., Van Bogaert, P., Detry, P., De Wulf, A., 2014. Terrestrial laser scanning as a key element in the integrated monitoring of tidal influences on a twin-tube concrete tunnel. The Photogrammetric Record, Vol. 29 (148), pp. 402-416, December 2014, DOI: 10.1111/phor.12080. Photogrammetric Record TERRESTRIAL LASER SCANNING AS A KEY ELEMENT IN THE INTEGRATED MONITORING OF TIDAL INFLUENCES ON A TWIN-TUBE CONCRETE TUNNEL TIMOTHY NUTTENS (Timothy.Nuttens@gmail.com) CORNELIS STAL (Cornelis.Stal@UGent.be), Department of Geography, Ghent University, Belgium HANS DE BACKER (Hans.DeBacker@UGent.be) KEN SCHOTTE (Ken.Schotte@UGent.be) PHILIPPE VAN BOGAERT (Philippe.VanBogaert@UGent.be), Department of Civil Engineering, Ghent University, Belgium PIERRE DETRY (Pierre.Detry@tucrail.be) Lines & Environment Unit, Topografie cel, TUC RAIL, Brussels, Belgium ALAIN DE WULF (Alain.DeWulf@UGent.be) Department of Geography, Ghent University, Belgium Abstract In 2012, for the first time in Belgium, integrated monitoring was carried out to assess the deformations of a twin-tube tunnel below the River Scheldt in Antwerp under the influence of estuarine tides. Levelling measurements during a tide cycle showed a variation in the height of levelling bolts of up to 10 mm between low and high tide. Simultaneous strain-gauge measurements also showed a significant difference in strains. A deformation of the tunnel section during each twice-daily tide cycle, resulting in an eccentric ‘egg’ or ‘pumpkin’ shape, could hold large risks for the strength and durability of the tunnel structure. However, laser scanning results showed that there were no significant