On the development of effective heave pressure in deep excavations

The processes and factors that underpin the development of effective heave pressure (EHP) at the base of deep excavations in soft soils have been numerically quantified for two idealised soil–structure systems, namely, a building unit cell and a tunnel geometry, using the finite-element method. Charts were developed exploiting dimensional analysis to estimate the impact of normalised time between the end of excavation and the completion of the restraining structure at the base, on the emerging magnitude of EHP for several scenarios where the excavation geometry, ground profile, relative stiffness and retaining wall length were varied. The results of the analyses were in good agreement with available data from physical model tests and the monitoring data of a deep excavation in Gothenburg, Sweden. Complementary analyses of site-specific background settlements and water table levels demonstrate that the charts developed are conservative. The results of this study can, within the limitations of the scenarios studied, readily be used for estimations of EHP in the preliminary design stage, and as a complement to detailed, project-specific analyses.