3D numerical back-analysis of an instrumented underpass road

Abstract

Purpose This paper aims to focus on three-dimensional (3D) numerical simulation of a monitored urban underground road consisting of diaphragm walls supported by one row of temporary steel struts and a cover slab in the central area. In addition to the lateral wall displacements, the analysis focuses on the load development in the struts and the evolution of the total stresses at the soil–wall interface, and highlights the 3D effect on the behavior of the structure. Design/methodology/approach Computation by back-analysis has become an important contribution to the understanding of observed phenomena. In this context, this paper investigates a full 3D numerical back-analysis of diaphragm wall deformation using the finite difference code FLAC3D. Findings The instrumentation allows a deep understanding of the ground response and the soil-structure interaction phenomena. It also provides an opportunity to validate numerical models. Using a soil model with simple failure criteria, the wall displacements are strongly influenced by the soil deformation modulus. The strut stiffness considerably influences the wall behavior. The geometrical effects have a significant impact on the induced wall displacements. Originality/value In the present study, the main soil geotechnical characteristics were deduced from laboratory and in situ tests. However, Young’s modulus of the soil has been adjusted to take account of the unloading effect. In the same context, the non-linearity of the elastic characteristics of the steel struts has been taken into account by modeling the struts using their experimental stiffness instead of their theoretical rigidity.

3D numerical analysis of pile response due to soil movements induced by an adjacent deep excavation

“…At the final phase of excavation, the maximum axial load and normalized pile settlement of the 2 D analysis overestimates the 3 D results by about 38 and 36%, respectively, respectively. These differences may be due on the one hand to the fact that the multipropped deep excavations are in nature threedimensional problems (Wang et al, 2010;Hong et al, 2015;Houhou et al, 2019Houhou et al, , 2021, and on the other hand to the simulation of the pile itself. Indeed in the plane strain model, it is not possible to represent the 3 D effect of a pile because of the difficulty in selecting adequate pile parameters.…”