Back analysis of the original design predictions by using tunnel face mapping, in-situ measurements and numerical modelling - A1 Lugoj-Deva motorway tunnels

Summary

Abstract

In order to predict the stability of the future excavated tunnels in the project of LOT2 Lugoj-Deva motorway tunnels project, this paper integrates geotechnical information with the results of numerical simulations. The numerical modelling of the tunnel excavation with the primary lining is based on a finite element numerical simulation approach. The objective of the present study goal was to verify the current design and recommend new tunnel support systems that would make excavation safer, more economical, and more efficient. The objectives encompassed the incorporation of additional input parameters update and the re-examination of previously accessible data. The constitutive model of the hardening soil and the input parameter list utilized by the designer during the initial design were both accepted. In addition to the hardening soil model, a classical sophisticated constitutive law, elastic-perfectly plastic model was incorporated. A series of modifications were made to the input material parameters for this reason. Ultimately, it became evident during the excavation of the tunnels that they had traversed a significantly weak rock mass, which was in direct opposition to the predicted overconsolidated soil mass. The following section will provide a synopsis of the advanced numerical modelling of the finally proposed tunnel support systems in both two-dimensional (2D) and three-dimensional (3D) formats. Furthermore, a range of innovative tunnel support types were implemented throughout the excavation process, based on the “design as you go” philosophy and in-situ experiences. The present study provides a comprehensive overview of the tunnel mapping, the geotechnical monitoring system, and the preliminary findings.