ABSTRACT
The TBM excavation for the Eastern extension of the Warsaw line II metro has been completed in January 2018 by Astaldi/Gulermak joint venture. Excavation involved mainly fine and medium sands below water table which created a challenging environment for Earth Pressure Balance (EPB) TBM works. In order to reduce settlements at ground level for selected historical buildings, ground improvement was carried out through permeation grouting with the aim at reducing volume loss during excavation and inducing an initial heave of the buildings. Also, high-standard TBM performance was achieved with the use of bentonite and polymers, specific grout mix and controlled face and grout pressures. Extensive monitoring was carried out through manual and automatic measurements and results showed small movements of the buildings and very small damage. This paper is aimed at describing the challenges faced for the TBM excavation, the adopted solutions and the most relevant results.
