Numerical modelling of the Ivens shaft construction in Lisbon, Portugal

Abstract

The traditional use of shafts is that of simple geotechnical structures, built to provide direct access to the subsoil to either access existing facilities, or to provide a launch chamber for new excavations. More recently, shafts have been constructed with complex geometries and directly incorporated as part of a permanent basement or metro station. One such complex structure is the Ivens shaft in Lisbon, Portugal, which is yet to be built. The construction of this shaft represents a geotechnical challenge due to its complex shape and location in central Lisbon, surrounded by several historic buildings and having in its close vicinity the Baixa-Chiado metro station. This paper presents a sophisticated 3D numerical simulation of the Ivens shaft construction, with a focus on assessing its effect on the existing buildings and the metro station and on the structural forces induced in its lining. The importance of integrating in the analysis the appropriate constitutive modelling of the different formations, the realistic initialisation of the ground conditions and the stiffness of the buildings, is discussed in detail. Although this is a class A prediction of a specific case study, it provides an insight into the general soil-structure interaction of a complex underground excavation.

Assessing the Sustainability of Alternative Shaft Construction Methods

“…Prior to the construction of the ring beam (Figure 4a,b), the shaft deflected, almost like a cantilever, with its rotating point below the base of the excavation, suggesting that the panels might have deformed, at least to some extent, independently. After the construction of the ring beam (Figure 4c,d), it is possible to observe some bulging in the middle and lower portions of the diaphragm wall, while the displacements in the upper part remained approximately constant, which is typical of this type of structure [53].…”

Displacement Analyses of Diaphragm Wall in Small-Scale Deep Excavation Considering Joints between Panels

“…Schwamb et al [22] conducted numerical analyses to investigate the performance of a circular shaft during construction. Pedro et al [23] evaluated the impact of an elliptical deep excavation on the surrounding buildings using 3D finite element analysis. However, the majority of the previous studies did not concentrate on the small-scale deep excavations mentioned above.…”

“…However, the modelling process is relatively time-consuming, and structural forces of diaphragm walls have to be calculated from the stresses at element integration points, which makes the whole process cumbersome in a practical design situation. For the aforementioned reasons, the joints between panels were typically disregarded in numerical modelling [16][17][18][19][20][21][22][23].…”