| Summary: |
Excavations in urban developed areas were commonly supported by diaphragm walls with
internal braces or tieback anchors. There are still required the necessary civil works to serve the
demands and also to solve the environmental problems. Wales and cross-lot struts are by far the
predominant method for wall support, the large working space inside the excavation provided
by a tieback anchor system has a significant construction advantage. This paper aims to evaluate
the soil stiffness parameters of the alluvial Taipei soil for tie-back diaphragm wall based on
back analysis of case study. The case histories of the Taipei County Administration Centre
(TCAC) and NTU Hospital (NTUH) were studied in this paper. The deformation analysis was
carried out by available finite element analysis tool using PLAXIS. In the analysis, beam
element method together with an elastic perfect plastic soil model was used to design the
diaphragm wall and the tieback anchor system. The soil was modelled as Mohr-Coulomb
model. According to the basic design, the clay deposits are modelled as undrained behaviour
while silty-sand behaves in drained condition. The simulation results show that the maximum
horizontal movement occurred at around the bottom of wall. At the final stage of construction,
the root mean square deviation (RSMD) between measured and calculated the wall movement
was 4% and 7% respectively at TCAC and NTUH sites. It was concluded that tied-back
diaphragm wall can be satisfactorily modelled using elasto-plastic Mohr-Coulomb soil model.
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