Application of EPS to Mitigate Ground Movements Caused by Mechanized Tunneling

Tunnel excavation leads to ground settlement and may cause existing buildings to suffer damage due to excessive deformation. Researchers proposed and studied several protective measures to mitigate the risk of damage to above-ground structures. Concrete and steel diaphragm walls effectively reduce the foundation settlement and are considered successful in protecting nearby structures. Compressing compressible material has advantages as the cost and environmental issues are considered. This study aims to investigate the effectiveness of geofoam buffer in reducing surface movement by conducting two-dimensional numerical analyses. Following verification of finite-element analysis through instrumental readings of the Isfahan subway case, numerical models were developed to determine barrier characteristics' effectiveness on the ground deformation. Analysis results show that the pre-installation of the geofoam diaphragm adjacent to the buried tunnel significantly mitigates the ground surface settlement; however, some adverse effects may be developed in the zone behind the Expanded Polystyrene (EPS) diaphragm wall.