Abstract
This paper presents a benchmark of a rate-dependent constitutive model for soft soils, implemented in a 2D finite element code, against the response of an instrumented excavation in sensitive clay: Göta Tunnel in Gothenburg. The monitoring data, which comprise time-series of pore water pressures, displacements, earth pressures and strut forces, provide valuable insights of the time-dependent response during the construction period. The long-term response, in terms of the ongoing settlement rates, is assessed using remote sensing data. The results of the numerical simulations demonstrate that the constitutive model, Creep-SCLAY1S, is capable of capturing the observed response. The trends of vertical and horizontal displacements are captured well until the stage of dewatering, and the evolution of pore pressures and earth pressures is computed with high accuracy, excluding peaks in the measurement values arising from pile and rock anchor installation. Most importantly, the results demonstrate that the rate-dependent model enables to model the complete service life of the tunnel, from construction of the excavation to the tunnel operation, with one unified model parameter set. Furthermore, the comparisons highlight the importance of assessing installation effects both in the choice of construction methods and modelling.
Highlights
The increasing demand for infrastructure systems in urban areas, such as railway tunnels, underground water retention systems and deep basements, requires accurate predictions of earth pressures and de formations of retaining structures to facilitate a safe and optimised design
For the stage after the pile installation, any differences between the measurements and computed results are considered to be an effect of the simplified modelling of the pile installation process by prescribing volumetric strains
This clearly is an over simplification, as the results indicate that the “smearing” in the 2Dmodel underestimate the stiffness response of the clay that in the field can partially arch around the cavities
Summary
The increasing demand for infrastructure systems in urban areas, such as railway tunnels, underground water retention systems and deep basements, requires accurate predictions of earth pressures and de formations of retaining structures to facilitate a safe and optimised design. Optimisation is desirable both for economic reasons, as well as essential in minimising the environmental impact of the construction and the permanent structure itself. The long-term performance is assessed by exploiting remote sensing data from recent InSAR satellite measurements
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