Large Scale Experimental Settlement Tests to Evaluate Structural Models for Tunnelling-Induced Damage Analysis (original) (raw)
Related papers
Case Study of Damage on Masonry Buildings Produced by Tunneling Induced Settlements
International Journal of Architectural Heritage, 2014
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.
Experimental analysis of a masonry façade subject to tunnelling-induced settlement
Engineering Structures, 2012
The increase of tunnel excavations in urban areas calls for improved methods to assess the risk of damage on existing buildings. Laboratory tests performed in a controlled environment provide a better insight of the parameters governing the structural response and can be used as validation of computational models. This paper presents an experiment carried out on a 1/10th scaled masonry façade subject to tunnel induced settlement. The results demonstrate the determinant effects of soil structure interaction, presence of openings and brittle masonry cracking on the final damage, with crack width up to 6.3 mm for a maximum applied settlement of 10 mm.
Géotechnique
Heritage masonry structures require detailed monitoring during nearby underground construction, to address the concerns of building owners and mitigate uncertainties relating to the soil–structure system. This paper discusses innovative displacement and strain monitoring of a listed masonry church undergoing ground movements due to nearby tunnelling in London Clay. In addition to conventional surveying and tilt monitoring, laser scan displacement monitoring and fibre optic strain sensing was conducted. Prior to construction, point clouds of the structure were used to map pre-existing geometric distortions in the structure. During construction, detailed monitoring of displacements and strains was conducted across the building facades and the tower. The same techniques were also used to monitor the painted dome of the church where conventional displacement monitoring was not feasible. With a focus on the new engineering insight provided by the innovative monitoring techniques, the imp...
2021
The development of urban mobility implies the construction of tunnels, often interacting with valuable historical structures. It is thus necessary to develop rational and reliable procedures to estimate the potential excavation-induced damage, dealing with complex soil-structure interaction problems. Classical approaches are often characterised by relatively simple schematisations for either one or both components of the problem, as, for example, springs for the soil or equivalent plates for the structure. Such simplified assumptions prove to be appropriate for simple soil-foundation cases, while show several limitations when tackling more complex problems, as those involving the excavation in the vicinity or beneath historical masonry structure. In such cases, the need for reliable prediction of the potential damage on surface structures induced by construction activities justifies the adoption of advanced numerical approaches. These need to be based on realistic constitutive assumptions for both soils and masonry elements and require the definition of the three-dimensional geometry as well as an accurate modelling schematisation of the excavation process. In this paper a 3D Finite Element approach is proposed to model in detail the excavation of twin tunnels, accounting for the strongly non-linear soil behaviour, interacting with monumental masonry structures, carefully modelling their geometry and non-linear anisotropic mechanical behaviour. The work focuses on a specific case-study related to the ongoing construction of the line C of Rome underground.
Tunnelling-induced deformation and damage on historical masonry structures
Géotechnique, 2014
The analysis of deformation and damage mechanisms induced by shallow tunnelling on masonry structures is carried out using an integrated, geotechnical and structural, numerical approach based on two-dimensional finite-element analyses. The masonry construction, schematised as a block structure with periodic texture, is regarded at a macroscopic scale as a homogenised anisotropic medium. The overall mechanical properties display anisotropy and singularities in the yield surface, arising from the discrete nature of the block structure and the geometrical arrangement of the blocks. The soil is modelled by means of a linear elastic-perfectly plastic model. The numerical analyses are performed assuming plane strain and plane stress conditions for the soil and the masonry structure, respectively. A displacement-controlled technique is adopted to simulate the tunnel construction, which produces settlement troughs in agreement with the empirical Gaussian predictions at different volume losses under free-field conditions. In order to test the numerical approach, a preliminary set of parametric analyses is carried out considering a simple masonry wall, characterised by different geometrical and mechanical properties, founded on a clayey deposit. Then, the case study of the Felice aqueduct in Rome (Italy), undercrossed by two tunnels of a new metro line, is considered. Significant differences are observed between the uncoupled analysis, where displacements predicted under free-field conditions are simply applied at the foundation level of the structure, and the interaction-based one, the latter being characterised by a reduced amount of tensile plastic strain. Numerical results in terms of vertical displacements at the ground level and on the structure are found to be in good agreement with monitoring data, thus validating the numerical model for this class of soil-structure interaction problems.
IEEE Transactions on Consumer Electronics - IEEE TRANS CONSUM ELECTRON, 2012
The assessment of settlement induced damage on buildings during the preliminary phase of tunnel excavation projects, is nowadays receiving greater attention. Analyses at different levels of detail are performed on the surface building in proximity to the tunnel, to evaluate the risk of structural damage and the need of mitigation measures. In this paper, the possibility to define a correlation between the main parameters that influence the structural response to settlement and the potential damage is investigated through numerical analysis. The adopted 3D finite element model allows to take into account important features that are neglected in more simplified approaches, like the soil-structure interaction, the nonlinear behaviour of the building, the three dimensional effect of the tunnelling induced settlement trough and the influence of openings in the structure. Aim of this approach is the development of an improved classification system taking into account the intrinsic vulnerability of the structure, which could have a relevant effect on the final damage assessment. Parametrical analyses are performed, focusing on the effect of the orientation and the position of the structure with respect to the tunnel. The obtained results in terms of damage are compared with the Building Risk Assessment (BRA) procedure. This method was developed by Geodata Engineering (GDE) on the basis of empirical observations and building monitoring and applied during the construction of different metro lines in urban environment. The comparison shows a substantial agreement between the two procedures on the influence of the analyzed parameters. The finite element analyses suggest a refinement of the BRA procedure for pure sagging conditions.
3D analytical prediction of building damage due to ground subsidence produced by tunneling
Tunnelling and Underground Space Technology, 2015
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.
Assessment of Excavation-Induced Building Damage
Earth Retention Conference 3, 2010
Ground movements during excavation have the potential for major impact on nearby buildings, utilities and streets. Increasingly ground movements are controlled at the source. They are assessed by linking the ground loss at the excavation wall to the volume change and displacements in the soil mass, and then to the lateral strains and angular distortion in structural bays or units, and are related to damage using a damage criterion based on the state of strain at a point. Numerical and physical models of excavation-induced building damage were used to vary parameters and develop procedures for assessing distortion and damage. Examples of building distortion and damage are presented for brick bearing wall structures of the 1800's and early 1900's, as well as later frame structures, that illustrate how geometry, era of construction, stiffness, and condition influence building response to ground movement.
Impact of the Crossrail tunnelling project on masonry buildings with shallow foundations
Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, 2019
Building monitoring and protection are important components of underground projects in urban areas. Typically the procedures applied for the assessment of settlement-induced damage to buildings are based on simplified assumptions that do not take into account soil–structure interaction. Assessment methods based on the relative stiffness between the structure and the soil exist, but they are rarely applied in practice due to concerns about the accuracy and reliability. The primary aim of this work is to use the large amount of monitoring data provided by the Crossrail project in London to improve understanding of building performance and existing damage assessment methods. The paper gives an initial overview of the available monitoring data by presenting four representative case studies for load-bearing masonry buildings on shallow foundations. Structural data are then used to evaluate the consistency of predictions produced by different relative stiffness formulations. The results s...