Real-time assessment of tunnelling-induced damage to structures within the building information modelling framework

During the initial design phases of complex multi-disciplinary systems such as urban tunnelling, the appraisal of different design alternatives can ensure optimal designs in terms of costs, construction time, and safety. To enable the evaluation of a large number of design scenarios and to find an optimal solution that minimises impact of tunnelling on existing structures, the design and assessment process must be efficient, yet provide a holistic view of soil-structure interaction effects. This paper proposes an integrated tunnel design tool for the initial design phases to predict the ground settlements induced by tunnelling and building damage using empirical and analytical solutions as well as simulation-based meta models. Furthermore, visualisation of ground settlements and building damage risk is enabled by integrating empirical and analytical models within our Building Information Modelling (BIM) framework for tunnelling. This approach allows for near real-time assessment of structural damage induced by settlements with consideration of soil-structure interaction and non-linear material behaviour. Furthermore, because this approach is implemented on a BIM platform for tunnelling, first, the design can be optimised directly in the design environment, thus eliminating errors in data exchange between designers and computational analysts. Secondly, the effect of tunnelling on existing structures can be effectively visualised within the BIM by producing risk-maps and visualising the scaled deformation field, which allows for a more intuitive understanding of design actions and for collaborative design. Having a fully parametric design model and real-time predictions therefore enables the assessment and visualisation of tunneling-induced damage for large tunnel sections and multiple structures in an effective and computationally efficient way

A Framework for Risk-Based Cost-Benefit Analysis for Decision Support on Hydrogeological Risks in Underground Construction

Construction below the ground surface and underneath the groundwater table is often associated with groundwater leakage and drawdowns in the surroundings which subsequently can result in a wide variety of risks. To avoid groundwater drawdown-associated damages, risk-reducing measures must often be implemented. Due to the hydrogeological system\u27s inherent variability and our incomplete knowledge of its conditions, the effects of risk-reducing measures cannot be fully known in advance and decisions must inevitably be made under uncertainty. When implementing risk-reducing measures there is always a trade-off between the measures\u27 benefits (reduced risk) and investment costs which needs to be balanced. In this paper, we present a framework for decision support on measures to mitigate hydrogeological risks in underground construction. The framework is developed in accordance with the guidelines from the International Standardization Organization (ISO) and comprises a full risk-management framework with focus on risk analysis and risk evaluation. Cost-benefit analysis (CBA) facilitates monetization of consequences and economic evaluation of risk mitigation. The framework includes probabilistic risk estimation of the entire cause-effect chain from groundwater leakage to the consequences of damage where expert elicitation is combined with data-driven and process-based methods, allowing for continuous updating when new knowledge is obtained

海洋環境にあるシールドトンネルのライフサイクル信頼性設計と評価

早大学位記番号:新8235早稲田大

Probabilistic cost-benefit analysis for mitigating hydrogeological risks in underground construction

Leakage of groundwater into underground facilities can subsequently cause groundwater drawdown, subsidence and subsidence damages to the built-up environment. In order to reduce the risk of damage, measures to mitigate the risks must often be implemented. The aim of this paper is to describe and demonstrate a probabilistic cost-benefit analysis approach to assess the economic profitability of investing in different risk mitigation alternatives. Since underground construction is always associated with uncertainties, the analysis uses probability distribution functions for uncertain parameters and Monte Carlo simulations to quantify probabilities of damage and implementation costs. The proposed approach is exemplified with a case study, the road tunnel project Bypass (F\uf6rbifart) Stockholm in eastern Sweden, for which four risk mitigation alternatives were evaluated. In conclusion, the approach helps to highlight the economic effects of different risk mitigation approaches and constitute a transparent support for decisions on implementation of risk mitigation. For the case study, the analysis indicates that the implementation costs of ∼ 7000 MSEK (700 million EUR) for risk mitigation needed to fulfil the legal requirements, from the Swedish Land- and Environmental court, in the form of ambitious sealing strategies are disproportionate relative to the benefits of ∼ 50 MSEK (5 million EUR) gained in the form of reduced damage risk for the built-up environment. In other words, billions SEK of taxpayers\u27 money are spent on unnecessary expenses to fulfill legal requirements without societal benefits. The novelty of the paper constitutes the coupling of models and combination of established methods for management of hydrogeological risks

A simulation-based software to support the real-time operational parameters selection of tunnel boring machines

With the fact that the main operational parameters of the construction process in mechanized tunneling are currently selected based on monitoring data and engineering experience without exploiting the advantages of computer methods, the focus of this work is to develop a simulation-based real-time assistant system to support the selection of operational parameters. The choice of an appropriate set of these parameters (i.e., the face support pressure, the grouting pressure, and the advance speed) during the operation of tunnel boring machines (TBM) is determined by evaluating different tunneling-induced soil-structure interactions such as the surface settlement, the associated risks on existing structures and the tunnel lining behavior. To evaluate soil-structure behavior, an advanced process-oriented numerical simulation model based on the finite cell method is utilized. To enable the real-time prediction capability of the simulation model for a practical application during the advancement of TBMs, surrogate models based on the Proper Orthogonal Decomposition and Radial Basis Functions (POD-RBF) are adopted. The proposed approach is demonstrated through several synthetic numerical examples inspired by the data of real tunnel projects. The developed methods are integrated into a user-friendly application called SMART to serve as a support platform for tunnel engineers at construction sites. Corresponding to each user adjustment of the input parameters, i.e., each TBM driving scenario, approximately two million outputs of soil-structure interactions are quickly predicted and visualized in seconds, which can provide the site engineers with a rough estimation of the impacts of the chosen scenario on structural responses of the tunnel and above ground structures

Sensitivity of urban buildings to tunneling-induced settlements

Tunneling construction represents an alteration to the distribution of soil pressures that will almost inevitably generate ground subsidence, which can endanger the adjacent buildings in urban areas. The risk of building damage can be substantially reduced with a comprehensive preliminary damage assessment during tunnel design phases, in combination with excavation techniques that minimize ground subsidence. The present research aims to increase the knowledge concerning the analytical and numerical techniques for building damage prediction related to tunneling. The thesis starts with the study of a real case of masonry building affected by the construction of the L9 metro line tunnel in Barcelona. Data available made possible to develop 2D and 3D numerical models of the building. The latter includes also the soil, the lining and interface models to simulate the contact between the building and the ground. The predicted crack patterns and opening widths in walls were verified by comparison to real damage reports. The case study also allowed a back analysis of the classical analytical prediction techniques based in the equivalent beam concept from Burland and Wroth. Analytical predictions of building damage are typically done for building walls aligned transversally or longitudinally with respect to the tunnel axis. These buildings are statistically representative, since many urban tunnels follow the tracks of avenues or streets. However, there is a significant number of buildings randomly aligned with respect to tunnel axes, in particular when using a Tunnel Boring Machine. For these buildings, the application of the classical analytical methodology can be done only with approximations, which can lead to unrealistic damage assessments. For this reason, a novel equation for the determination of ground strain has been developed. This equation allows the application of the classical settlement Gaussian profiles and the equivalent beam method in 3D, i.e. for buildings located in whichever position with respect to the tunnel axis. In addition, the model allows considering the position of the tunnel heading, which increases the realism of the settlement trough generated by tunnel construction. Another detected issue during the present research was the high sensitivity of both analytical and numerical damage predictions to certain parameters related to the characterization of ground. In the case of analytical predictions, the modeling of settlement troughs by Gaussian curves offers numerous mathematical advantages. However, the simplicity of this approximation leads to substantially different estimations of damage for small variations of the governing parameters. For this reason, the use of reliability-based methods can be useful for the assessment of building damage. In this way, the present thesis shows the development of a probabilistic model for the prediction of tunneling-induced damage. A procedure to determine the maximum allowable settlements that are used as monitoring threshold values of the construction process is also included. Furthermore, it is shown how the prediction of ground behavior and the allowable settlements can be updated with a Bayesian method by incorporating measurements made during the construction.La construcció de túnels representa una alteració de la distribució de pressions del sòl que, de manera pràcticament inevitable, genera assentaments en superfície. Aquests poden provocar danys en edificis, especialment en zones urbanes. No obstant, aquest risc es pot reduir substancialment mitjançant la correcta predicció dels danys en les fases de disseny del túnel, juntament amb l¿ús de tècniques d'excavació que minimitzin els assentaments induïts. La present recerca aprofundeix en la metodologia de predicció de danys en edificis afectats per la construcció de túnels urbans. La tesi comença amb l'estudi d'un edifici real d'obra de fàbrica afectat per la construcció del túnel de la línia L9 del metro de Barcelona. Mitjançant les dades disponibles, s'han realitzat models numèrics en 2D i 3D de l'edifici. Aquest últim inclou a més el sòl, el túnel i un conjunt d'elements d'interfície que simulen el contacte entre l'edifici i el terreny. Els patrons de fissuració predits pel model han estat comparats amb aixecaments dels danys fets durant les obres. L'estudi d'aquest cas ha permès també l'aplicació i verificació de les tècniques de predicció de danys en edificis basades en el concepte de la biga equivalent ideat per Burland i Wroth durant la dècada dels 70. Les prediccions analítiques de dany en edificis es duen a terme generalment assumint els edificis posicionats transversalment o longitudinalment respecte l'eix del túnel. El nombre d'edificis que compleix aquesta hipòtesi és estadísticament representatiu, ja que molts túnels segueixen la traça dels carrers o les avingudes de les ciutats. Tot i així existeix un gran nombre d'edificis alineats arbitràriament respecte l'eix del túnel, especialment quan la construcció del túnel es realitza mitjançant l'ús de tuneladores (Tunnel Boring Machines - TBM). Per aquests edificis, l'aplicació de la metodologia analítica clàssica es pot efectuar només mitjançant aproximacions, la qual cosa pot implicar estimacions poc realistes dels danys. Per aquest motiu, s'ha desenvolupat una nova equació per al càlcul de la deformació del terreny. Aquesta equació permet l'aplicació dels perfils Gaussians d'assentament clàssics i del model de la biga equivalent en 3D, és a dir, en edificis ubicats en qualsevol posició respecte l'eix del túnel. A més, el model permet considerar la posició del front d'excavació, incrementant així el realisme del camp d'assentaments generat per la construcció del túnel. Un altre aspecte important detectat durant la recerca és l'extrema sensibilitat de les prediccions dels danys segons els valors dels paràmetres relacionats amb la caracterització del terreny. La modelització del camp d'assentaments mitjançant perfils Gaussians ofereix una sèrie d'avantatges matemàtics, però tot i així, la simplicitat del model comporta diferències notables en l'estimació dels danys si s'efectuen petites variacions dels paràmetres d'entrada. És per això que les tècniques de fiabilitat estructural poden ser útils per a l'estimació dels danys. En aquesta línia, la tesi mostra un model probabilístic per a la predicció dels danys provocats en edificis degut a la construcció de túnels. L'aplicació de tècniques de fiabilitat estructural permet a més la determinació dels llindars d'assentament que s'utilitzen durant el procés constructiu. En cas de tenir mesures prèvies d'assentaments de la zona d'estudi, es mostra també com el comportament del terreny i aquests valors llindars poden actualitzar-se a través d'un mètode Bayesià

Advanced Theoretical and Computational Methods for Complex Materials and Structures

The broad use of composite materials and shell structural members with complex geometries in technologies related to various branches of engineering has gained increased attention from scientists and engineers for the development of even more refined approaches and investigation of their mechanical behavior. It is well known that composite materials are able to provide higher values of strength stiffness, and thermal properties, together with conferring reduced weight, which can affect the mechanical behavior of beams, plates, and shells, in terms of static response, vibrations, and buckling loads. At the same time, enhanced structures made of composite materials can feature internal length scales and non-local behaviors, with great sensitivity to different staking sequences, ply orientations, agglomeration of nanoparticles, volume fractions of constituents, and porosity levels, among others. In addition to fiber-reinforced composites and laminates, increased attention has been paid in literature to the study of innovative components such as functionally graded materials (FGMs), carbon nanotubes (CNTs), graphene nanoplatelets, and smart constituents. Some examples of smart applications involve large stroke smart actuators, piezoelectric sensors, shape memory alloys, magnetostrictive and electrostrictive materials, as well as auxetic components and angle-tow laminates. These constituents can be included in the lamination schemes of smart structures to control and monitor the vibrational behavior or the static deflection of several composites. The development of advanced theoretical and computational models for composite materials and structures is a subject of active research and this is explored here for different complex systems, including their static, dynamic, and buckling responses; fracture mechanics at different scales; the adhesion, cohesion, and delamination of materials and interfaces

Tunneling-induced ground movement and building damage prediction using hybrid artificial neural networks

The construction of tunnels in urban areas may cause ground displacement which distort and damage overlying buildings and services. Hence, it is a major concern to estimate tunneling-induced ground movements as well as to assess the building damage. Artificial neural networks (ANN), as flexible non-linear function approximations, have been widely used to analyze tunneling-induced ground movements. However, these methods are still subjected to some limitations that could decrease the accuracy and their applicability. The aim of this research is to develop hybrid particle swarm optimization (PSO) algorithm-based ANN to predict tunneling-induced ground movements and building damage. For that reason, an extensive database consisting of measured settlements from 123 settlement markers, geotechnical parameters, tunneling parameters and properties of 42 damaged buildings were collected from Karaj Urban Railway project in Iran. Based on observed data, the relationship between influential parameters on ground movements and maximum surface settlements were determined. A MATLAB code was prepared to implement hybrid PSO-based ANN models. Finally, an optimized hybrid PSO-based ANN model consisting of eight inputs, one hidden layer with 13 nodes and three outputs was developed to predict three-dimensional ground movements induced by tunneling. In order to assess the ability and accuracy of the proposed model, the predicted ground movements using proposed model were compared with the measured settlements. For a particular point, ground movements were obtained using finite element model by means of ABAQUS and the results were compared with proposed model. In addition, an optimized model consisting of seven inputs, one hidden layer with 21 nodes and one output was developed to predict building damage induced by ground movements due to tunneling. Finally, data from damaged buildings were used to assess the ability of the proposed model to predict the damage. As a conclusion, it can be suggested that the newly proposed PSO-based ANN models are able to predict three-dimensional tunneling-induced ground movements as well as building damage in tunneling projects with high degree of accuracy. These models eliminate the limitations of the current ground movement and building damage predicting methods

Managing hydrogeological risks in underground construction

Groundwater leakage into underground constructions can cause groundwater drawdown and subsequently costly damages to objects impacted by changes in groundwater conditions. In order to reduce the damage risk, risk-reducing measures can be implemented. When implementing measures, society’s limited resources must be carefully managed by balancing the costs and the benefits (e.g. reduced risk) of the measures. Decisions regarding risk-reducing measures must always be taken under uncertainty since the conditions of the hydrogeological system cannot be fully known. In this thesis, a generic framework for management of hydrogeological risks in underground construction is presented (Paper 1). This framework constitutes a structured and transparent approach to the decision process for implementation of risk-reducing measures for groundwater control in underground construction. The framework uses a stochastic and iterative approach for managing the changing level of uncertainty inevitably associated with underground construction. The different modules that constitute the framework are also exemplified by application in a case study (paper 2). The case study focuses on the risk of subsidence damages to the built-up environment (buildings, paved surfaces and pipes) and risk-reducing measures in the form of sealing, artificial recharge and reinforcement measures to houses. The framework and methods used within the framework for the risk analysis and risk evaluation have proven useful as decision support for management of hydrogeological risks. The framework has also proven to be an efficient tool in communication of risks both internally in a project but also between the project owner and stakeholders in the society