Settlement behaviour and watertightness evaluation of immersion joints in immersed tunnel on soft soil: A case study of the Noordtunnel

¹ Directorate General of Highways, Ministry of Public Works, Jakarta, Indonesia
² Department of Geoscience and Engineering, Delft University of Technology, Delft, The Netherlands
³ Rijkswaterstaat, Ministry van Infrastructure en Waterstaat, Utrecht, The Netherlands
⁴ Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Abstract

Immersed tunnels are widely used to cross waterways and are typically constructed in deltaic regions where soft soil conditions prevail. Despite careful design, immersed tunnels founded on soft soil may experience excessive and differential settlements, which may lead to structural cracking or leakage during long-term operation. Understanding the settlement behaviour of immersed tunnels on soft soil therefore remains critical for ensuring tunnel structural safety and serviceability. This study investigates the settlement behaviour of the Noordtunnel, an immersed tunnel in the Netherlands that has been in operation for over three decades. Field settlement data were first compiled and analysed. Then, two-dimensional numerical models were developed using two soil constitutive models to simulate settlements from construction stage to long-term service conditions, including the effects of riverbed sedimentation above the tunnel roof. Model calibration and sensitivity analyses were conducted to verify predictive reliability. The findings indicate that the observed differential settlements are primarily attributed to the presence of soft subsoil layers and ongoing riverbed sedimentation. The implications of differential settlement for tunnel watertightness, particularly at immersion joints, are subsequently assessed.