Evaluation of soil constitutive model on braced excavation support behaviour

For this project, a two dimensional finite element analysis using PLAXIS was conducted to evaluate the performances of two types of soil stress-strain model, namely, Mohr-Coulomb model and the Hardening Soil model for excavations in clay. The results from these two models were compared in regards to the best fit E_u/C_u ratio, maximum wall deflection, ground settlement and strut forces. The best fit E_u/C_u ratio was plotted against various parameters such as Plasticity Index (PI), Undrained Shear Strength (Cu), Factor of Safety (Fs) as well as (Cu/(σ_v^' )) to obtain correlations. A total of seven case studies with complete soil data were used for analysis. In order to obtain the best fit E_u/C_u ratio for both the Mohr-Coulomb model and the Hardening Soil model, models were created by varying the Eu values from the available Cu data. The best fit E_u/C_u ratio model would have the one with the closest fit with the actual measured wall deflection. The results show that using the Mohr-Coulomb model for excavation analysis in clay tend to produce higher values for the best fit E_u/C_u ratio. Also, using the Mohr-Coulomb model tends to produce smaller initial settlement but larger final settlement. In addition, using the Mohr-Coulomb model tends to produce 10~30% more strut forces than using the Hardening Soil model. Lastly, there is a downward sloping trend when the best fit E_u/C_u ratio is plotted against (Cu/(σ_v^' )).Bachelor of Engineerin