Derivation of model parameters for numerical analysis of the Ivens shaft excavation

Abstract

The prediction of induced ground movements and the potential damage to existing structures and services is paramount when building deep excavations in an urban environment. In order to obtain a reasonable prediction advanced constitutive models need to be employed, so that the behaviour of the soil can be adequately reproduced under different stress conditions. The calibration of such models is complex and often requires optimisation, as a large number of parameters need to be determined from the available ground investigation data, while also ensuring their consistency with the initial ground conditions. This paper presents the calibration process of advanced constitutive models employed to simulate the excavation of the Ivens shaft in Lisbon, Portugal. The data from both historic and new laboratory and field testing is employed in the calibration procedure. In order to assess and validate the suitability of the derived model parameters, a back-analysis of the nearby Baixa-Chiado metro station excavation is carried out and its results are presented and discussed

Integrating laboratory and field testing into advanced geotechnical design

“…= 875, would increase only the elastic shear modulus, without changing the degradation part of the shear stiffness, which is mainly driven by mobilised plasticity in the model. However, the effect of sample disturbance, as discussed by Tatsuoka & Shibuya (1991), or Pedro et al (2017), should be reflected at all strain levels, although at varying degrees. This was achieved by changing the parameters of the hardening modulus of the model, increasing the modelled stiffness to values given by the assumed variation with strain of the ratio 0 / 0 .…”

Dataset on the behaviour of the Areolas da Estefania formation in Lisbon and its modelling using a state-dependent soil model

“…The samples tested were extracted from two boreholes performed in the backyard of the Quintão building, Lisbon, Portugal [ 6 , 7 ] at depths of 8 m, 18 m and 21 m. At the indicated depths, a 76 mm-diameter thin-walled sampler with a PVC liner was used to retrieve intact samples. In order to characterize the particle size distribution, traditional sieving and sedimentation tests as set out in the standard BS 1377-2 [8] were undertaken.…”

Numerical modelling of the Ivens shaft construction in Lisbon, Portugal

“…The excavation of the West gallery of the Baixa-Chiado station is simulated with a slightly modified sequence, involving only a top heading and a bench, for simplicity. The actual excavation involved more stages in both the West and East galleries (top heading, side drifts and multiple benches), which were all simulated in the 2D FE validation analysis reported in Pedro et al (2017). Furthermore, the plane of symmetry along the axis between the two galleries in the current 3D FE analysis implies that these are excavated simultaneously, whereas the process was sequential in the 2D analysis and in the field (West gallery first).…”

“…Based on the interpretation of ground conditions by Pedro et al (2018), the choice of appropriate constitutive models and their calibration were presented and discussed in Pedro et al (2017). The same reference also shows a validation of the adopted constitutive modelling, employing a 2D finite element analysis in the case study of the Baixa-Chiado station construction which benefited from the field monitoring of ground movements during construction (both West and East galleries).…”

“…before the construction in the field takes place. The numerical study presented here builds on carefully performed site investigation and characterisation of the ground conditions, reported by the authors in Pedro et al (2017Pedro et al ( , 2018.…”