Application Of Compound Deep Cement Mixed Walls For Retaining Structures In Excavations

Deep cement mixed (DCM) columns are widely used as retaining structures to support deep excavations due to low cost and their ability in reducing seepage. However, the tensile strength of DCM walls is very low. Hence, large wall sections are necessary to avoid development of high tensile stresses when DCM walls are used to support deep excavations. In this paper application of compound DCM walls, which integrate DCM walls and bored piles, to support deep excavations are investigated aiming to develop resilient design methods for compound DCM walls. Three- dimensional finite element modelling is used in simulating the wall behaviour during deep excavations, considering the full geometry of the compound DCM wall. Numerical model is validated using a case study of a compound DCM wall constructed in Shanghai, China. Finally the use of arched DCM walls with different curvatures in between bored piles is investigated. Results of this study clearly demonstrates the advantages and limitations of increased curvature of compound DCM walls with respect to both ground deformations surrounding the excavation and tensile stresses developed in the compound DCM wall.