Evaluation of the wall deflections of a deep excavation in Central Jakarta using three-dimensional modeling

Abstract

This paper presents a case study and numerical simulations regarding a large-scale deep excavation in Central Jakarta, Indonesia, and its three-dimensional (3D) effects on wall deformation. The soil profile in Central Jakarta is generally soft to firm alluvial clay overlying stiff to hard alluvial and diluvial clay. In this study, the geotechnical engineering properties of soil (i.e., undrained shear strength and modulus) were established using data from a site investigation, in situ and laboratory tests, and empirical correlations with standard penetration numbers (SPT-N). A summary of simplified soil input properties for subsurface soil in Central Jakarta was provided. To analyze the deep excavation case, a 3D finite element model was developed by considering a top-down construction method, a supporting system of concrete slabs, and the influence of the soil modulus. The numerical results indicated that the hardening soil model with the soil modulus obtained from in situ pressuremeter tests yields reasonable predictions for excavation-induced wall deformation. The applicability of 3D finite element analyses to capturing the 3D corner effect on the wall deformation was validated. According to the parametric study, the plane strain ratio (PSR) was determined for the excavations in Jakarta clay. Compared with the PSR developed for Taipei clay, this study revealed that the PSR value was influenced not only by the 3D corner effect but also by the stiffness of the subsurface soil. In addition to PSR, the wall deflection path was also affected by the 3D corner effect and soil modulus.