Stability of excavations supported by diaphragm walls

• Main Author: Lim, Zheng En
• Other Authors: Goh Teck Chee, Anthony
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/74517
• Institution: Nanyang Technological University

With the constant demand and scarcity of land in Singapore, developments have been going deep underground. Braced excavation is a commonly used engineering technique to ensure that the excavation holds up as construction underground continues. There is a need to ensure accuracy and reliability in the computation of excavation stability so that the bracing supports can be adequately designed for. Different methods of calculating excavation stability has been developed over the years, with traditional methods like Bjerrum & Eide (1956). These methods, however, make many assumptions, some of which has significant effects on excavation stability. More sophisticated finite element methods have also been developed, to assess basal heave stability. The Hardening Soil (HS) Model was utilised in this study. The HS model has the ability to simulate the non-linear stress strain behaviour of soil and it considers the stiffness of soil. Using the HS model in PLAXIS 2D, the Basal Heave Factor of Safety was calculated, and the trends were analysed in this study to understand the effects of various parameters that affected the excavation stability. The parameters that were studied were the wall embedment depth D, excavation width B, wall interface ratio α-interface and wall stiffness EI. The Eide, Aas & Josang (1972) method was also compared with the Hardening Soil model to compare the differences in both methods. An equation was also developed to provide a faster way of computation using the FSEide values to bring it to closer agreement with the values obtained from the finite element model.