Characteristics of diaphragm wall lateral deformations and ground surface settlements: Case study in Iran-Ahwaz metro

The effect of deep excavation on lateral deformation of diaphragm walls and on the ground surface settlement adjacent to the excavation in five metro stations in the southwestern section of the Ahwaz metro was evaluated. In one of these stations (Kargar Square Station) the ground surface settlement around the station and the lateral deformation of the top of the diaphragm wall were measured in three stages during excavation to a depth of 5 m. After construction work was suspended in this section of the metro, numerical methods were used to predict the ground surface settlement and the lateral wall deformation that would be caused by excavation at depths between 5 m and 17.2 m. The measured data were used to back calculate soil parameters required for this analysis. The ground surface settlement and the lateral deformation of the wall in all these stations that would result from excavation to a final depth of 17.2 m below ground were predicted using the back calculated parameters. The relationship between the maximum ground surface settlement and the distance to the wall for all five stations of the Ahwaz metro was predicted. The predictions were found to fall in zones I and II of the Peck chart. The surface settlement and the lateral wall deformation and their influence on adjacent buildings were predicted and compared with similar projects around the world. The effect of settlement on adjacent buildings in one of these stations was predicted to cause at most superficial damage, unlikely to have structural significance.

► Effects of excavation on the lateral deformation and surface settlement are studied.
► The back analysis method was used to obtain improved estimates of model parameters.
► The research was conducted in order to document the field behavior of Ahwaz geology.
► Maximum settlements of the ground fall in the regions I and II of the Peck diagram.
► Surface settlement is generally inferior to the lateral deformation in soft soils.