Numerical Study on Pile Load Behavior During the Construction of an Underground Passage in Singapore Soft Clay Applying Piled Grout Slab

Abstract

This paper presents a numerical study on design considerations concerned with the axial loads of piles plugged in grouted slab, which are applied to the construction of a cut-and-cover tunnel in Singapore soft clay deposits. The main purpose of this study is to verify the effects of the deformation and current consolidation characteristics of Singapore Marine Clay on the numerical evaluation of pile load as well as the ground response. Two-dimensional finite element analyses were carried out on the basis of the effective stress principle; construction procedures were simulated in a short-term manner, and the subsequent consolidation of the ground was modeled as a long-term behavior. Results of numerical simulation indicated that the piled grout slab significantly enhanced the basal stability during the excavation, and the axial behavior of pile varies with the construction phases by exerting tension during excavation and compression in subsequent construction phases. Related to the tension load estimation, undrained elastic behavior of Marine Clay in unloading-reloading stage was found to be significant due to the dominant unloading stress-path of soil near the piles at the passive side of the excavation. In addition, the on-going consolidation state of Marine Clay that presumed based on the modified Cam-Clay model exhibited significant effects on predicting the long-term compressive behavior of piles because of dissipation of inherent excessive pore water pressure in the Marine Clay.