Possible Damages in Diaphragm Wall During Braced Excavation

Reinforced concrete diaphragm walls are widely used in underground constructions as temporary or permanent earth retaining structures. In the design and analysis of braced excavations, the diaphragm wall is normally assumed as linear elastic material, considering that the deformation is small during the construction process. However, limited field measurements suggested that the concrete wall could be damaged during the construction process due to large curvature of the deformation. Reduced elastic stiffness has been used to consider this effect, but this approach is too empirical and neglects the detailed physical mechanism. In this paper, the mechanical behavior of the reinforced concrete diaphragm wall panel is modelled in details in the braced excavation analysis. The concrete is represented by the damaged concrete plasticity model to consider the possible damage caused by both compression and tension under large deformation. Detailed finite element analyses are then conducted to investigate possible damages in the diaphragm wall during braced excavation process. Computed results clearly identify the location and magnitude of the damages in the diaphragm wall during every stage of the construction process. Comparison with the conventional elastic wall analysis demonstrates the advantage of the proposed approach. This study suggests that damages in the concrete structures should be considered carefully in the design and analysis of some critical projects.

Keywords: Diaphragm wall, Damages, Braced excavation.