Performance of Buttress Wall in a Deep Excavation in Soft Ground

Diaphragm wall strengthened with buttress panels has frequently been adopted for reducing the wall deflections and the adjacent ground surface settlements caused by deep excavations. A case history on top-down construction with the excavation depth of 32 m is reviewed to study the effect of the buttresses on reduction in wall deflections. The excavation was supported by perimeter diaphragm walls of 1.5 m in thickness, 52 m in length and stiffened with buttresses spacing at 8.75 m. Two-Dimensional numerical analyses using the nonlinear Hardening-Soil with Small-Strain Stiffness constitutive soil model have been conducted. Five sets of wall stiffnesses with different interface reduction factors have been adopted to simulate buttresses with various spacing. Close matching between the computed wall deflections with those observed in the inclinometers validated the set of the soil stiffness parameters for the Hardening-Soil with Small-Strain Stiffness model. The effectiveness of the buttresses was assessed by comparing the computed wall deflections with and without the buttress panels.