In many tunnel designs, reinforced concrete tunnel lining design is selected based on construction requirements rather than design loads. A constant cross-section is typically used along a tunnel even if the design loads change from one location to another, especially for tunnels constructed by tunnel boring machines (TBM). Factor of safety against failure is not constant along the length of tunnel and is typically high at shallow depth regions. Factor of safety during a rare event is usually much less than the ones set for service load states. Rare events such as earthquake, train derailment, explosion and long duration fires do not happen daily and generally a minor reparable damage is targeted at the structure during those types of events. The focus of this study is to analytically investigate structural fire safety of reinforced concrete circular tunnel linings in terms of reduction in service load safety and to develop recommendations for preliminary assessment of structural fire endurance of circular tunnel linings. Analytical methods accounting for thermal non-linearity, material degradation, tunnel lining-ground interaction and fire time stages are available to assess the structural fire safety of the concrete tunnel linings. Analytical results are determined to be in good agreement with tunnel key segment hydrocarbon fire test.

The use of sprayed concrete lining is common in tunneling practice since it allows the application of non-circular tunnel sections and complex tunnel intersections. Low capital cost of construction equipment is also an important factor for the selection of the sprayed concrete lining. In general the use of sprayed concrete lining is referred as New Austrian Tunneling Method (NATM). Depending on the requirements regarding tunnel heading stability and limitations on tunneling induced soil displacements, tunnel cross sections often advanced by different construction sequences and round lengths in NATM. For the purpose of assessing the effects of excavation sequence, round length, soil stiffness and tunnel depth on surface settlements and on tunnel lining forces, a parametric study has been carried out, considering short-term and long-term soil response. Three dimensional finite element analysis are performed to model the excavation sequence and stress distribution around the tunnel lining during excavation. The parameters used in the parametric study can be listed as: tunnel diameter, tunnel depth, round length and soil stiffness. Existing analytical and empirical solutions, which are used for prediction of ground subsidence due to tunneling and forces on tunnel lining, are also reviewed in this study / and their predictions are compared with the results obtained from numerical analysis. This comparison also provides an opportunity to evaluate the performance of the existing efforts. The variations between the results obtained from different methods are discussed and it is concluded that the limitations of the existing methods are the primary reason of the variations between results.

In today&rsquo / s world, buried structures are used for a variety of purposes in many areas such as transportation, underground depot areas, metro stations and water transportation. The serviceability of these structures is crucial in many cases following an earthquake / that is, the earthquake should not impose such damage leading to the loss of serviceability of the structure. The seismic design methodology utilized for these structures differs in many ways from the above ground structures. The most commonly utilized approach in dynamic analysis of underground structures is to neglect the inertial forces of the substructures since these forces are relatively insignificant contrary to the case of surface structures. In seismic design of these underground structures, different approaches are utilized like free-field deformation approach and soil-structure interaction approach. Within the confines of this thesis, seismic response of highway tunnels is considered through a case study on Bolu Tunnels, which are well documented and subjected to D&uuml / zce earthquake. In the analyses, the seismic response of a section of the Bolu tunnels is examined with 2-D finite element models and results are compared with the recorded data to evaluate the capability of the available analysis methods. In general, the results of analyses did not show any distinct difference from the recorded data regarding the seismic performance of the analyzed section and that the liner capacities were sufficient, which is consistent with the post earthquake condition of the Bolu Tunnels.

Le travail de thèse propose une nouvelle approche du dimensionnement courant des tunnels. Par le biais d'une double démarchehiérarchique, en terme de méthode de calcul d'une part et en terme de loi de comportement d'autre part, différentes lois d'endommagement sont proposées afin de mieux comprendre la mécanique du creusement-soutènement

Many contemporary states and historic political entities walled their borders stressing the idea that these barriers would protect their homelands from external threats and thus, achieve security. Although this security argument has prevailed, the political science literature fails to offer a systematic empirical examination of the relationship between barriers and cross-border threats. This research attempts to bridge this gap by answering the question: What are the actual security outcomes of physical barriers on borders? And thus, under what conditions do barriers succeed/fail to achieve security? This paper posits that, in some cases, building barriers on borders to stop non-state actors’ attacks escalate conflict. It demonstrates that when militants have supply institutions, they will manage to increase their attacks and shift to new tactics despite the barrier. It also studies the Israeli Gaza Strip Fence and offers an analysis based on patterns of the relationships between features of the barrier and the Gaza attacks. these patterns are derived from a quantitative dataset built by the researcher and are also supplemented by qualitative data about the case. / text

published_or_final_version / Applied Geosciences / Master / Master of Science

Prediction of groundwater inflow into rock tunnels is one of the essential tasks of tunnel engineering. Currently, most of the methods used in the industry are typically based on continuum models, whether analytical, semi-empirical, or numerical. As a consequence, a regular flow along the tunnel is commonly predicted. There are also some discrete fracture network methods based on a discontinous model, which typically yield regular flow or random flow along the tunnel. However, it was observed that, in hard rock tunnels, flow usually concentrates in some areas, and much of the tunnel is dry. The reason is that, in hard rock, most of the water flows in rock fractures and fractures typically occur in a clustered pattern rather than in a regular or random pattern. A new method is developed in this work, which can model the fracture clustering and reproduce the flow concentration. After elaborate literature review, a new algorithm is developed to simulate fractures with clustering properties by using geostatistics. Then, a discrete fracture network is built and simplified. In order to solve the flow problem in the discrete fracture network, an existing analytical-numercial method is improved. Two case studies illustrate the procedure of fracture simulation. Several ideal tunnel cases and one real tunnel project are used to validate the flow analysis. It is found that fracture clustering can be modeled and flow concentration can be reproduced by using the proposed technique. / text

Due to the inherent uncertainties in ground and groundwater conditions, tunnel projects often have to face potential risks of cost overrun or schedule delay. Risk analysis has become a required tool (by insurers, Federal Transit Administration, etc.) to identify and quantify risk, as well as visualize causes and effects, and the course (chain) of events. Various efforts have been made to risk assessment and analysis by using conventional methodologies with precise probabilities. However, because of limited information or experience in similar tunnel projects, available evidence in risk assessment and analysis usually relies on judgments from experienced engineers and experts. As a result, imprecision is involved in probability evaluations. The intention of this study is to explore the use of the theory of imprecise probability as applied to risk analysis in tunneling. The goal of the methodologies proposed in this study is to deal with imprecise information without forcing the experts to commit to assessments that they do not feel comfortable with or the analyst to pick a single distribution when the available data does not warrant such precision. After a brief introduction to the theory of imprecise probability, different types of interaction between variables are studied, including unknown interaction, different types of independence, and correlated variables. Various algorithms aiming at achieving upper and lower bounds on previsions and conditional probabilities with assumed interaction type are proposed. Then, methodologies have been developed for risk registers, event trees, fault trees, and decision trees, i.e. the standard tools in risk assessment for underground projects. Corresponding algorithms are developed and illustrated by examples. Finally, several case histories of risk analysis in tunneling are revisited by using the methodologies developed in this study. All results obtained based on imprecise probabilities are compared with the results from precise probabilities. / text

published_or_final_version / abstract / toc / Transport Policy and Planning / Master / Master of Arts in Transport Policy and Planning

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