Construction Cost Estimation for Greek Road Tunnels in Relation to the Geotechnical Conditions

The accurate assessment of a tunnel construction’s basic cost is of major importance of the entire financial appraisal of the overall project. Thus, efficient tools and analyses addressing this particular issue can provide significant information (even from the preliminary stages of tunnel design) and assist in the whole decision making process throughout the project’s design life. The paper presents the analysis of tunnel construction cost with respect to the excavation process and the temporary support measures used. These support systems have been determined to be the most influential factors when assessing the total cost of the tunnelling project. More specifically, the analysis is based on the data gathered from the construction of 5 Greek road tunnels, where the construction cost has been estimated from respective crosssections representative of a variety of geotechnical conditions. The assessment is made to reflect current unit prices (2011), so as to establish a common reference point for all tunnels under evaluation. Cost figures are presented in terms of cost per meter (€/m) and cost per cubic meter (€/m3). Consequently, the findings of the analysis could be used as a preliminary construction cost estimation tooling in order to provide design engineers and project managers a rapid and representative estimation that can be in other similar underground construction projects in Greece and perhaps similar construction projects internationally

Path dependence in technologies and organizations : a concise guide

The note on which an entry for the Palgrave Encyclopedia of Strategic Management will draw offers a beginner’s guide to path dependency in technologies and organizations. We address the very meaning of the concept and its centrality in various aspects of economic analysis. We outline the various levels of the economic system where it is observable, its sources, consequences and different formal representations of path dependent processes

Time-Dependent Behavior of Rock Materials

Understanding the geomechanical behavior of a geological model is still an on-going challenge for engineers and scientists. More challenges arise when considering the long-term behavior of rock materials, especially when exposed to environments that enable time-dependent processes to occur and govern overall behavior. The latter is essential in underground projects such as nuclear waste repositories. The lifespan can exceed one million years or other openings where the project’s lifetime and sustainability are the critical design parameter. In such cases, progressive rock mass deformation that can lead to instabilities, time-dependent overloading of support and delayed failure are considered the product of time-dependent phenomena. Understanding and predicting the overall impact of such phenomena aims to achieve design optimization, avoiding dlivery delays and thus cost overruns. This chapter provides more insight into the time-dependent behavior of rocks. Simultaneously, the emphasis is given to investigating and analyzing creep deformation and time-dependent stress relaxation phenomenon at the laboratory scale, and in-depth analyses are presented. This work further develops the understanding of these phenomena, and practical yet scientific tools for estimating and predicting the long-term strength and the maximum stress relaxation of rock materials is presented. The work presented in this chapter advances the scientific understanding of time-dependent rock, and rock mass behavior increases the awareness of how such phenomena are captured numerically and lays out a framework for dealing with such deformations when predicting tunnel deformations

Statistical interpretation of tunnel project characteristics and their influence on technical risks – current and future challenges

Tunnels are an increasingly significant part of our built infrastructure. Simultaneously, they are subject to a diversity of inherent uncertainties associated with the geotechnical, hydro-geological, and physical environment surrounding them. The associated risks can materialize on many occasions, leading to disasters with substantially high reinstatement costs, incurred delays, and damage to adjacent third-party assets and the environment. Such disasters can occur due to extreme natural events and unforeseen and unforeseeable ground conditions or accidents. but also, human-driven issues, such as substandard design, poor project management, aggressive project timelines leading to safety shortcuts, compressed budgets and application of innovative techniques not yet fully tested and validated, are some factors contributing to an increased probability of risk materialization and disastrous events. This paper aims to provide a statistical interpretation of tunnel project characteristics and their influence on technical risks based on a database with approximately 400 tunnel failure cases. A further goal of the study is to support decision-makers in the risk management process, such as owners, engineers, and insurers by improving their understanding of project sensitivities. The results indicate the significance of technical characteristics (such as tunnel dimensions, construction type, and ground formations). Still, they also reveal some dependence between lower project risks and the application of current project and risk management practices

Cost Overruns in Tunnelling Projects: Investigating the Impact of Geological and Geotechnical Uncertainty Using Case Studies

Tunnelling projects seldom meet the initial budget requirements. Commonly, these types of projects suffer from cost overruns, which subsequently lead to project delivery delays mainly due to unsuccessful ground investigation as specified in the literature. The presented work scrutinises the effect of ground investigation in cost overruns. More specifically, various cost figures (total cost, construction cost, tunnel cost) are analysed for two case studies i) the Channel tunnel in the UK and ii) the Olmos Tunnel in Peru. Clayton’s relation between ground investigation and the construction cost is utilised and further investigated. In the Channel tunnel, the main problems faced led to a cost overrun of 78% for the total cost, 66% for the construction cost and 77% for the tunnelling cost. In the Olmos tunnel, two main geological scenarios are analysed and the construction cost overrun is calculated at 9.6% and 6.7%. Drawing on the conclusions, this research work proves that ground investigation can be one of the major factors influencing the tunnel cost

Assessing TBM performance in heterogeneous rock masses

A major challenge that TBM performance is requested to deal with for a successful and effective progress is tunnelling through lithologically and geomechanically heterogeneous rock masses. Such heterogeneous environments are common and recent tunnel examples in the UK include the Hinckley Point C offshore cooling tunnels being driven through interbedded carbonaceous mudstone/shales and argillaceous limestone and the Anglo American’s Woodsmith Mine Mineral Transport System tunnel in Redcar Mudstone with beds of ironstone. This inherent geological heterogeneity leads to difficult tunnelling conditions that initially stem from predicting a sound and representative ground model that can be used to preliminary assess the TBM performance. In this work, an exhaustive review of existing TBM Penetration Rate (PR) methods identified that no models address the issue of parameter selection for heterogeneous rock masses comprising layers with different rock strengths. Consequently, new approaches are required for estimating rock mass behaviour and machine performance in such environments. In the presented work the Blue Lias Formation (BLI), which is characterised by its layered rock mass, comprising very strong limestone, interbedded with weak mudstone and shales, is investigated. BLI formation is considered herein being a representative example of lithological heterogeneity. Based on the fieldwork carried out in three localities in the Bristol Channel Basin (S. Wales and Somerset), geological models are produced based on which a geotechnical model is developed, and four ground types are determined. Implications of the current findings for TBM performance are assessed, including faulting, groundwater inflow and excavation stability with a particular focus on both PR and advance rate. A modified approach using the existing empirical models is proposed, developed and presented in this paper that can be used as a guide to determine TBM performance in heterogeneous rock masses reducing the risk of cost and time overruns

Analysis of time-dependent deformation in tunnels using the Convergence-Confinement Method

During the excavation of a tunnel the accumulated wall displacement and the loading of tunnel support is the result of both the tunnel advance (round length and cycle time) and the time-dependent behaviour of the surrounding rock mass. The current approach to analyze the tunnel wall displacement increase is based on the Convergence-Confinement Method (CCM) performed with either analytical (closed form solutions) or the usage of the Longitudinal Displacement Profiles. This approach neglects the influence of time-dependency resulting in delayed deformation that may manifest even minutes or hours after excavation. Failure to consider the added displacements in the preliminary design can result in false selecting the time of installation and the type of support system causing safety issues to the working personnel, leading to cost overruns and project delivery delays. This study focuses on investigating and analyzing the total displacements around a circular tunnel in a visco-elastic medium by performing an isotropic axisymmetric finite difference modelling, proposing a new yet simplified approach that practitioners can use taking into account the effect of time

Diverse novel phleboviruses in sandflies from the Panama Canal area, Central Panama

The genus Phlebovirus (order Bunyavirales, family Phenuiviridae) comprises 57 viruses that are grouped into nine speciescomplexes. Sandfly-transmitted phleboviruses are found in Europe, Africa and the Americas and are responsible for febrile illness and infections of the nervous system in humans. The aim of this study was to assess the genetic diversity of sandflytransmitted phleboviruses in connected and isolated forest habitats throughout the Panama Canal area in Central Panama. In total, we collected 13 807 sandflies comprising eight phlebotomine species. We detected several strains pertaining to five previously unknown viruses showing maximum pairwise identities of 45–78 % to the RNA-dependent RNA polymerase genes of phleboviruses. Entire coding regions were directly sequenced from infected sandflies as virus isolation in cell culture was not successful. The viruses were tentatively named La Gloria virus (LAGV), Mona Grita virus (MOGV), Peña Blanca virus (PEBV), Tico virus (TICV) and Tres Almendras virus (TRAV). Inferred phylogenies and p-distance-based analyses revealed that PEBV groups with the Bujaru phlebovirus species-complex, TRAV with the Candiru phlebovirus speciescomplex and MOGV belongs to the proposed Icoarci phlebovirus species-complex, whereas LAGV and TICV seem to be distant members of the Bujaru phlebovirus species-complex. No specific vector or habitat association was found for any of the five viruses. Relative abundance of sandflies was similar over habitat types. Our study shows that blood-feeding insects originating from remote and biodiverse habitats harbour multiple previously unknown phleboviruses. These viruses should be included in future surveillance studies to assess their geographic distribution and to elucidate if these viruses cause symptoms of disease in animals or humans.The genus Phlebovirus (order Bunyavirales, family Phenuiviridae) comprises 57 viruses that are grouped into nine speciescomplexes. Sandfly-transmitted phleboviruses are found in Europe, Africa and the Americas and are responsible for febrile illness and infections of the nervous system in humans. The aim of this study was to assess the genetic diversity of sandflytransmitted phleboviruses in connected and isolated forest habitats throughout the Panama Canal area in Central Panama. In total, we collected 13 807 sandflies comprising eight phlebotomine species. We detected several strains pertaining to five previously unknown viruses showing maximum pairwise identities of 45–78 % to the RNA-dependent RNA polymerase genes of phleboviruses. Entire coding regions were directly sequenced from infected sandflies as virus isolation in cell culture was not successful. The viruses were tentatively named La Gloria virus (LAGV), Mona Grita virus (MOGV), Peña Blanca virus (PEBV), Tico virus (TICV) and Tres Almendras virus (TRAV). Inferred phylogenies and p-distance-based analyses revealed that PEBV groups with the Bujaru phlebovirus species-complex, TRAV with the Candiru phlebovirus speciescomplex and MOGV belongs to the proposed Icoarci phlebovirus species-complex, whereas LAGV and TICV seem to be distant members of the Bujaru phlebovirus species-complex. No specific vector or habitat association was found for any of the five viruses. Relative abundance of sandflies was similar over habitat types. Our study shows that blood-feeding insects originating from remote and biodiverse habitats harbour multiple previously unknown phleboviruses. These viruses should be included in future surveillance studies to assess their geographic distribution and to elucidate if these viruses cause symptoms of disease in animals or humans

Stability Analysis of Shafts Used for Minewater Heat Recovery

Traditional heating using non-renewable energy resources contributes up to 50% of current carbon emission level. Different sources of renewable energy are being exploited and developed to lower the carbon emission level for continuity of healthy living environment. It is found that thermal energy is stored in minewater flooding abandoned mines. The minewater can be extracted through newly drilled boreholes or existing mineshafts. To ensure successful and sustainable operation, mineshafts have to be structurally stable. When the mines are abandoned, the water level tends to recover. Some of the configurations of the minewater heat recovery may change the temperature of part of the shaft wall. This research aims to provide some insight on the stability of mineshafts for minewater heat recovery through numerical sensitivity analyses on: (a) water level, (b) temperature fluctuations. In the presented research work, rock masses with different properties have been analyzed. Change in temperature is found to mainly change the static Young’s Modulus of intact rock and the joint roughness. However, the joint roughness is expressed indirectly using the Geological Strength Index, which has direct relationship with joint roughness and is used in stability analysis. It is found that an increase in water level reduces the integrity of the whole shaft. The degrees of stability deterioration are different at different depths and depend on the in situ stress state. Findings of this analyses can be assist in making a decision on the selection of the appropriate configuration for minewater heat recovery

Time-Dependent Model for Brittle Rocks Considering the Long-Term Strength Determined from Lab Data

The excavation of tunnels in brittle rocks with high in-situ strengths under large deviatoric stresses has been shown to exhibit brittle failure at the periphery of tunnels parallel to the maximum in-situ stress. This failure can either occur instantaneously or after several hours due to the strength degradation that is implicitly and indirectly considered in typical brittle constitutive models. While these models are powerful tools for engineering analyses, they cannot predict the time at which brittle rupture occurs, but rather, they show a possible failure pattern occurring instantaneously. In this paper, a model referred to as the long-term strength (LTS) model is introduced and implemented into FLAC2D. The model is built as a modified version of the CVISC model, introduced by Itasca, by adding a strength decay function. This function is developed from lab-scale time-to-failure (TTF) data. The LTS model is verified against its corresponding analytical solution using a constant stress creep lab test and implemented into a tunnel-scale model using the geometry, stress, and geologic conditions from the Atomic Energy of Canada Limited Underground Research Laboratory (AECL URL). The results of the LTS tunnel model are then compared to an identical model using the Cohesion Weakening Friction Strengthening (CWFS) approach