Displacement prediction of tunnels based on a generalised Kelvin constitutive model and its application in a subsea tunnel

• A tunnel lining displacement analytical expression with a time variable is derived.
• The final displacement of tunnel lining was forecast and analysed.
• A new method which can locate the monitoring cross-section of tunnel is proposed.

Soft rock has the characteristic of time dependency, namely, creep or rheology. When the tunnel is located in weak surrounding rock, due to the rheology properties of surrounding rock, the load on the tunnel support and the displacement of tunnel lining may continue to increase. If the tunnel does not receive timely reinforcement and repair, these problems may threaten the safe operation of the tunnel. For tunnel repair and maintenance, we want to install some displacement monitoring sections in the appropriate position. However, tunnels are linear underground structures, and it is challenging to determine the location of the monitoring section and the displacement monitoring standards. In this study, based on the state equation of the generalised Kelvin constitutive model, a tunnel lining displacement analytical expression with a time variable was derived. Using actual data obtained during the construction of a subsea tunnel in Xiamen City and the theoretical research results presented in this paper, the final displacement of the subsea tunnel lining was forecasted and analysed. According to the results of the prediction and when considering the geological conditions along the longitudinal axis of the tunnel, the location of monitoring cross sections and monitoring standards was given. In the end, the measured data and the prediction result were compared, which proves that the conclusion is reliable. This study provides a useful reference for the maintenance and repair of tunnels in rheology rock mass.