Design of the Vienna metro shaft: probabilistic analysis and settlement forecasting of the soil-structure system via Monte Carlo simulation

Abstract

Reliability and safety assessments require optimizing decision-making throughout the lifecycle of systems such as the “soil mass – underground structure” system. Changes in the engineering-geological environment cause various geohazards that must be identified and evaluated during the project development stage, taking into account both natural and anthropogenic factors related to subway construction and operation in dense urban environments. This article presents an analysis of shaft structures for the proposed Vienna metro line using numerical and probabilistic modeling, with particular emphasis on the quality of input data, their probabilistic variability, and their influence on the stress-strain state of the structures. Finite element modeling was performed using the PLAXIS software package, employing advanced elastoplastic Hardening Soil (HS) and Hardening Soil Small (HSS) ground models. By repeatedly varying initial soil parameters surrounding reinforced concrete tunnel structures, variation coefficients for key loads and deformations in both the structures and soil mass were obtained, which can inform the design of similar structures in the future. A methodology and algorithm for assessing the reliability of the “soil mass – underground structure” system were proposed, based on the Monte Carlo statistical method. The evaluation criterion is the probability of exceeding threshold values of additional vertical settlement after tunnel excavation in unfinished sections of the Vienna metro. This approach enables the prediction of additional deformations affecting the foundations of existing buildings impacted by tunneling. Finally, regression analysis was conducted to assess the influence of varying factors on stress-strain parameters derived from FEM calculations, using both linear and multivariate models.