An Innovative Earth Retaining Supported for Deep Excavation

Abstract

The U-shape wall is an innovative application of a composite buttress-cross wall to reduce excessive movements induced by excavation. The performance and mechanism of the U-shape wall in controlling the deformations were examined by three-dimension finite element analysis. The examination includes the buttress part treatment of the U-shape wall (i.e., demolished or maintained), the length of the buttress part, the depth of the cross part, and the deformation control mechanism of the U-shape wall. Results revealed that the buttress part treatment of the U-shape wall was insignificant. Moreover, the normalized depth of the cross part to final excavation depth ratio was 0.15–0.2 that can yield optimum performance. Also, the design of the length of the buttress part relies on the target value of the reduction. For example, with a 5m length of the buttress part, the deformations could be reduced by 60–80% from the case of without U-shape wall. The deformation control mechanism of the Ushape wall was notably contributed to the combined stiffness between the U-shape wall and the diaphragm wall.