Application of Hyperstatic Reaction Method for Designing of Tunnel Permanent Lining, Part I: 2D Numerical Modelling

The increase of bored tunnels in the entire world has raised the question how to design the tunnel structure in an efficient way. This paper proposes a numerical approach to the Hyperstatic Reaction Method (HRM) for analysing permanent tunnel linings. The permanent tunnel lining is known as main structure of tunnel maintenance during the time. The HRM is one of the analysis methods for tunnel lining in long term. In this paper, two dimensional numerical modelling is performed by considering hyperstatic reaction concepts. Loading is done after the calculation of long term loads, and ground reaction is simulated by springs. Designing is done for Manjil-Rudabar freeway project, Tunnel No. 2. The numerical analyses were performed for Operational Design Earthquake (ODE) and Maximum Design Earthquake (MDE) loading conditions. A new simplified approach is used for considering the effect of earthquake loading on the tunnel lining. Then, an interaction diagram between axial force and bending moment used for investigating the capacity of tunnel lining. The thickness of tunnel lining and armature are calculated for three sections based on induced forces in tunnel lining. These forces were different in every section according to the load combinations, rock mechanics properties, lining properties, and overburden.  The numerical results showed that the forces in tunnel lining for MDE condition is approximately 50% more than ODE condition in earthquake loading. This numerical processing presented that the HRM is a proper, fast, and practical method for designing and analysing the tunnel lining

Application of Hyperstatic Reaction Method for Designing of Tunnel Permanent Lining, Part II: 3D Numerical Modelling

Underground structures often have abrupt changes in structural stiffness or ground conditions such as junctions of tunnels, tunnel portal in slopes, and niches in road tunnels. At these locations, stiffness differences may subject the structure to differential movements and generate stress concentrations. Because of adversity in these issues, they need a three dimensional analysis. This paper proposes a numerical approach to the hyperstatic reaction method (HRM) for three dimensional analysis of permanent tunnel linings. In this paper, three dimensional numerical modelling is performed by considering hyperstatic reaction concepts. Designing is done for Manjil-Rudabar freeway project, Tunnel No. 2. The numerical analyses performed for Operational Design Earthquake (ODE) and Maximum Design Earthquake (MDE) loading conditions. Then interaction diagram between axial force and bending moment used for investigating the capacity of tunnel lining. The numerical results show that although more axial forces are created in tunnel lining for ODE condition, but the points in the P-M diagrams are located in the furthest distance to the diagram border (tunnel supporting system); because of less bending moment in this condition. Therefore, the safety factor in ODE condition is more than MDE condition. This numerical processing presented that the HRM is a proper, fast, and practical method for tunnel designers

Numerical modelling of ground-tunnel support interaction using bedded-beam-spring model with fuzzy parameters

The study of the ground-tunnel interaction by introducing a predetermined degree of variation (fuzziness) in some parameters of the chosen model is presented and discussed. This research comes from the consideration that tunnel model parameters and geometry are usually affected by a degree of uncertainty, mainly due to construction imprecision and the great variability of rock mass properties. The research has been developed by using the fuzzy set theory assuming that three model parameters are affected by a certain amount of uncertainty (defined by the so-called membership functions). The response of the numerical model is calculated by solving the fuzzy equations for different shapes of the membership functions. In order to investigate the effects of some model parameters, and to provide a simple procedure and tool for the designers, a study on the effect of tunnel boundary conditions, based on a fuzzy model, has been carried out using a simple but well known and widely used design method such as the bedded-beam-spring mode

Influence of the Tunnel Shape on Shotcrete Lining Stresses

Tunnel excavation is frequently carried out in rock masses by the drill and blast method and the final shape of the tunnel boundary can be irregular due to overbreaks. In order to investigate the effects of overbreaks a study of the effect of tunnel boundary irregularity has been carried out. This is done developing a computational tool able to take into account fuzzy variables (i.e., thickness of the beams of the bedded spring approach used for the model). The obtained results show that irregularity effects should be considered when a shotcrete lining is used as the final tunnel lining (for the case where the tunneling procedure does not permit a smooth surface to be obtained). This is crucial to obtain a durable linin

Numerical modelling of ground-tunnel support interaction using bedded-beam-spring model with fuzzy parameters

The study of the ground-tunnel interaction by introducing a predetermined degree of variation (fuzziness) in some parameters of the chosen model is presented and discussed. This research comes from the consideration that tunnel model parameters and geometry are usually affected by a degree of uncertainty, mainly due to construction imprecision and the great variability of rock mass properties. The research has been developed by using the fuzzy set theory assuming that three model parameters are affected by a certain amount of uncertainty (defined by the so-called membership functions). The response of the numerical model is calculated by solving the fuzzy equations for different shapes of the membership functions. In order to investigate the effects of some model parameters, and to provide a simple procedure and tool for the designers, a study on the effect of tunnel boundary conditions, based on a fuzzy model, has been carried out using a simple but well known and widely used design method such as the bedded-beam-spring model

ROBUST DESIGN OF SHIELD TUNNELS ‒ CONSIDERING THE LONGITUDINAL VARIATION OF INPUT PARAMETERS

This dissertation, aimed at developing an improved design methodology for shield tunnels that explicitly considers design robustness against longitudinal variation of input parameters (such as soil parameters). To this end, a new solution model for shield tunnel performance analysis was first developed. In this new model, the random field concept was employed to model the longitudinal variation of input parameters. The input parameters (in the longitudinal domain) that had been generated with Monte Carlo simulation (MCS) were used as inputs for the tunnel longitudinal behavior analysis. Here, the finite element method (FEM) based upon Winkler elastic foundation theory was employed. The analyzed tunnel longitudinal responses as well as the input parameters that had been generated with MCS were then used to study the performance (i.e., structure safety and serviceability) of tunnel segment rings. For the latter analysis, the force method was used. Finally, the robust design concept was integrated into the design of shield tunnels to guard against variation of tunnel performance caused by longitudinal variation of input parameters. Within the framework of robust design, a multi-objective optimization was performed aiming to optimize the design with respect to design robustness against longitudinal variation of input parameters and cost efficiency, while satisfying safety and serviceability requirements. Through illustrative examples, the effectiveness and significance of improved shield tunnel design methodology was demonstrated

Mesh-Free and Finite Element-Based Methods for Structural Mechanics Applications

The problem of solving complex engineering problems has always been a major topic in all industrial fields, such as aerospace, civil and mechanical engineering. The use of numerical methods has increased exponentially in the last few years, due to modern computers in the field of structural mechanics. Moreover, a wide range of numerical methods have been presented in the literature for solving such problems. Structural mechanics problems are dealt with using partial differential systems of equations that might be solved by following the two main classes of methods: Domain-decomposition methods or the so-called finite element methods and mesh-free methods where no decomposition is carried out. Both methodologies discretize a partial differential system into a set of algebraic equations that can be easily solved by computer implementation. The aim of the present Special Issue is to present a collection of recent works on these themes and a comparison of the novel advancements of both worlds in structural mechanics applications

Numerical analysis of traditionally excavated shallow tunnels

openLo scavo di gallerie rappresenta sicuramente una tra le sfide più impegnative che un ingegnere civile possa affrontare. Ciò è dovuto principalmente alla natura tridimensionale di questo problema di interazione terreno-struttura ma anche alle numerose incertezze che possono entrare in gioco nella progettazione. Recentemente, le tecniche di calcolo numeriche, che permettono una più ampia comprensione del problema, hanno subito un notevole sviluppo, diventando una risorsa fondamentale per la progettazione di scavi in sotterraneo. Tuttavia, solo ingegneri con una buona preparazione numerica sono in grado di gestire la modellazione di problemi di interazione terreno-struttura così complessi. Inoltre, tali modelli richiedono una attenta calibrazione dei parametri e una costante validazione con dati di monitoraggio. Lo scopo di questa tesi è quello di analizzare alcune delle principali problematiche legate alla progettazione di gallerie superficiali scavate in tradizionale. Il vantaggio principale dello scavo in traditionale rispetto a quello meccanizzato è legato alla maggiore flessibilità nella scelta dei rivestimenti e delle techniche di rinforzo del cavo e del fronte della galleria. Tuttavia, una maggiore flessibilità progettuale è necessariamente legata ad una profonda conoscenza del comportamento deformativo dell’ammasso, nonché ad un utilizzo consapevole delle tecniche modellazione numerica. Il presente lavoro è principalmente incentrato sulle seguenti tematiche riguardanti la progettazione di gallerie superficiali: - la stabilità di fronti di scavo rinforzati e non rinforzati; - l’applicabilità degli Eurocodici ad una progettazione condotta mediante tecniche di modellazione numerica; - la calibrazione dei parametri del modello numerico e la sua validazione attraverso dati di monitoraggio.Among the problems that civil engineers have to face, the design and verification of an underground construction is one of the most challenging. A tunnel engineer has to tackle with a complex three-dimensional soil-structure interaction problem where many factors and uncertainties come into play. This is the reason why professional experience and engineering judgment usually play a crucial role. In recent years, numerical calculation techniques, which can provide an important basis for a better understanding of the problem, have strongly improved. They have become a fundamental resource for underground construction design, but they also entail some drawbacks: - only engineers with a strong numerical background can handle complex soil-structure interaction problems; - numerical calculations, especially if 3D, can be very time-consuming; - material parameters should be carefully evaluated, according to the particular problem and adopted constitutive law; - numerical models need to be validated with field monitoring data. The goal of this thesis is to investigate the main issues regarding the applicability of numerical analyses to the design and verification of traditionally excavated shallow tunnels. Despite, the remarkable technological improvement in mechanised tunnelling, traditional techniques still represent, in some cases, the most suitable and convenient solution. The principal advantage of traditional techniques is the high flexibility in the choice of supports and reinforcement measures. However, design flexibility implies a deep understanding of the ground response to underground openings as well as a conscious use of numerical models. This work provides a contribution to the numerical design of shallow tunnels by focusing on three principal issues: - stability of reinforced and unreinforced excavation faces; - Eurocodes applicability to a numerically-based design; - parameters calibration and numerical validation through comparison with monitoring data.INGEGNERIA CIVILE, AMBIENTALE, EDILE E ARCHITETTURAPaternesi, AlessandraPaternesi, Alessandr