Mechanical properties of cellular diaphragm wall in deep excavations considering nonlinear contact between wall and soil

Cellular diaphragm (CD) wall, as a new kind of excavation supporting structure without internal bracing system, has not been well studied, despite its successful applications in many engineering practices. By incorporating the hyperbolic contact model into a commercial finite element software through FRIC subroutine, the finite element analysis of the mechanical properties of CD wall in sand is performed. Two contact models, i.e., the Mohr-Coulomb linear and hyperbolic nonlinear models, are adopted. The stress-strain behavior of sand is simulated using the user-defined hypoplastic model through UMAT subroutine. By comparing with that of the existing centrifuge test results, the performance of the proposed numerical model is validated. The results indicate that the nonlinear contact model adopted is superior to the linear contact model in capturing the performance of the CD wall during excavation. This is because that the nonlinear contact model has an ability to account for the nonuniform distribution of interfacial shear stress between the wall bottom and the surrounding soil as well as the stress concentration phenomenon in the critical part of the wall. The lateral earth pressure on the wall has not reached its ultimate state, and an obvious spatial distribution feature of the lateral earth pressure can be observed. The mode of the horizontal displacement of the wall is cantilever, while the mode of the vertical displacement at wall top can be regarded as integral rotation with the front-wall settling and the back-wall uplifting. The distributions of the bending moment in the middle of the back- and front-walls are similar. The results obtained are helpful for the design optimization of CD wall for supporting excavation.