Underground Singapore 2011 The interaction between the excavation and temporary retaining system is to be carried out using PLAXIS version 9.02. PLAXIS is a geotechnical finite element program intended for two-dimensional deformation and stability analysis. PLAXIS uses fully automated calculation procedures based on robust numerical methods. The program is able to model soil-structure interaction for excavations in a realistic simulation that closely follows the actual construction sequence. It allows the application of surcharge loads, point loads and also models changes in ground water pressures.
Figure 6 Result of analyses for wall bending moment
The soil behavior was modeled using Mohr- Coulomb Model, which is an elastic-perfectly plastic constitutive model. Tension cut-off option was activated to cut off all possible developed tension points in the soil elements. The CBP wall was modeled as beam elements with the corresponding axial and bending stiffness. Figure 5 show the typical model of the PLAXIS analyses. The result of analyses for wall bending moment and deflection are shown in Figures 6 and 7 respectively. In this project, the wall deflection for south wall is controlled by a limit of 50mm from LTA contractual requirement to limit movement of viaduct structure as shown in Figure 3. However the allowable deflection at north wall is greater, which is 140mm or 0.7% of total excavation depth as required by BCA.
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