This paper analyzes the structural response of a group of masonry buildings subjected to real ground movements experienced during the construction of the L9 Metro tunnel in Barcelona, bored by a Tunnel Boring Machine (TBM) -Earth Pressure Balance Machine (EPB). The studied one-storey small dwellings represent a common building typology frequently used in those days in Barcelona's outskirts (more than 1000 were erected). Real settlement profiles are compared with the ones provided by empirical methods, which estimate the shape and the area of the trough according to the ground properties and the volume loss (inherent to the tunneling construction method). The first aim of the paper is to evaluate the effectiveness of two techniques used to predict damages in buildings resulting from tunneling subsidence: 1) the 'equivalent beam' and its subsequent refinements, and 2) the appliance of a non-linear Finite Element macro-model. The real structural damage presented in the buildings is compared with the predictions given by this two methods. Main model parameters have been determined by means of characterization experiments developed on the site and in the laboratory, thus giving a much higher significance to the analysis. The obtained predictions present a high correspondence with the actual damage registered, particularly in crack pattern and in crack widths.
Tunnel construction entails the generation of ground settlements, which can endanger the adjacent buildings. The prediction of damages in buildings is usually based on the classical Gaussian profiles for the approximation of the subsidence trough and the equivalent beam method for modeling the response of building walls. Current available expressions refer to walls aligned transversally with respect to the tunnel axis, which usually represents the worst-case scenario. However, approximations must be done for other building alignments, since no analytical expressions are available for these cases. We propose a novel equation for the determination of the horizontal ground strain, which departs from the equations of the classical Gaussian settlement profiles. The novel formulation allows the application of the equivalent beam method in 3D and the modeling of the tunnel advance. The results show significant variations of the estimated damage depending on the wall position with respect to the tunnel axis. The paper reviews also certain relevant aspects of building damage predictions, such as the influence area of settlements and the possible contribution of ground horizontal strain to damage reduction. A parametric analysis is further performed to create a non-linear regression model that allows direct estimation of the maximum tensile strain in a building wall according to input values of geological conditions and wall and tunnel geometries.Peer ReviewedPostprint (author's final draft
Tunnel construction commonly causes deformations of the surrounding ground, which can endanger buildings and other structures located in the vicinity of the tunnel. The prediction of these deformations and damages to buildings is difficult, due to limited knowledge of geotechnical conditions and due to uncertainty in predicting the response of the structures to the settlements. This motivates the development of a probabilistic model for the prediction of tunneling-induced damage to buildings. We propose such a model, based on the classical Gaussian profiles for the approximation of the subsidence trough and the equivalent beam method for modeling the response of the building walls. In practice, settlements are commonly monitored through deformation measurements. To account for this, we present a Bayesian method for updating the predicted settlements when measurements are available. Finally, we show how maximum allowable settlements, which are used as threshold values for monitoring of the construction process, can be determined based on reliability-based criteria in combination with measurements. The proposed methodology is applied to a group of masonry buildings affected by the construction of the L9 metro line tunnel in Barcelona.
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