Methodology for the adaptation of the excavation and support system of a tunnel based on the observational method

O presente artigo aborda uma nova aplicação do método observacional na engenharia de túneis para a adaptação em tempo real do método de escavação e suporte. O método observacional é utilizado há muitos anos, no entanto não existe uma metodologia consistente e estruturada para a incorporação dos dados da monitorização na adaptação do sistema de suporte em tempo real. A metodologia proposta possibilitará a otimização do sistema de suporte e do custo total da obra, tal como um aumento da segurança nos trabalhos de escavação. Primeiramente, são propostos critérios limite para os deslocamentos e tensões no maciço. Durante a fase de projecto são construídos gráficos de suporte de consulta rápida durante a fase de construção para a realização da adaptação referida. Caso não existam gráficos disponíveis para a situação específica em análise, é necessário o recurso a cálculos de retroanálise. A metodologia foi aplicada ao túnel de “Bois de Peu”, composto por dois túneis paralelos com um comprimento superior a 500 m. Este caso de estudo apresentava um elevado nível de incerteza relativa à heterogenidade do solo e consequentemente à definição dos parâmetros geomecânicos. A metodologia foi aplicada em 4 secções embora se apresentem os resultados para apenas duas. Foi possível confirmar o potencial da aplicação da metodologia na adaptação em tempo real do sistema de suporte, assim como a importância de existir um plano de monitorização específico e de qualidade no aperfeiçoamento dos processos de retroanálise.This paper presents a new application of the observational method in tunneling engineering for real time adaptation of the excavation method and support systems. The observational method has been used for many years, however, a gap exists when referring to a consistent and structured approach for the incorporation of monitoring data in the real time adaptation of the support system. The proposed methodology will enable the optimization of the support system and the total cost of the work, and also an increased safety in excavation works. In a first step limit criteria for displacements and stresses for the soil/rock formation are proposed. The methodology uses graphics that are constructed during the project stage based on parametric calculations to assist in the process and when these graphics are not available, since it is not possible to predict every possible scenario, inverse analysis calculations are carried out. The methodology is applied to the “Bois de Peu” tunnel which is composed by two tubes with over 500 m long. High uncertainty levels existed concerning the heterogeneity of the soil and consequently in the geomechanical design parameters. The methodology was applied in four sections and the results focus on two of them. It is shown that the methodology has potential to be applied in real cases contributing for a consistent approach of a real time adaptation of the support system and highlight the importance of the existence of good quality and specific monitoring data to improve the inverse analysis procedure

Numerical analysis of the venda nova II hydroelectrical complex main caverns and backanalysis of the geomechanical parameters

Neste trabalho é apresentado um modelo numérico 3D para as cavernas principais do complexo da Venda Nova II considerando as diferentes fases de escavação. Os parâmetros geomecânicos do maciço granítico, para os modelos, foram calculados utilizando o software GEOPAT. Este programa é um sistema baseado em conhecimento que permite obter os parâmetros geomecânicos para a modelação de obras subterrâneas em maciços graníticos. Os resultados do modelo são comparados com os deslocamentos observados por intermédio de extensómetros ao longo das várias fases construtivas. Nesta comparação são utilizadas diversas ferramentas estatísticas para a validação dos resultados obtidos. Finalmente, é realizada a retroanálise de parâmetros geomecânicos do maciço rochoso utilizando um algoritmo de optimização inovador. Os resultados obtidos permitiram concluir que a estimativa inicial dos parâmetros apresenta uma precisão bastante aceitável e que o algoritmo possui uma boa robustez e eficiência.In this work a 3D numerical model for the main caverns of the Venda Nova II complex which considers the different excavation stages is presented. The geomechanical parameters for the numerical models were computed using GEOPAT. This software is a knowledge based system which allows evaluating geomechanical parameters for the modelling of underground works built in granite rock masses. The results are compared with the observed displacements measured with extensometers along the different construction stages. In this comparison several statistical tools are used for the validation of the obtained results. Finally, the backanalysis of geomechanical parameters of the interested rock mass is performed using an innovative optimization algorithm. The results show that the initial evaluation of the parameters presents a very acceptable accuracy and that the algorithm posses good robustness and efficiency.Fundação para a Ciência e a Tecnologia (FCT) - Projecto POCI/ECM/57495/2004, intitulado Geotechnical Risk in Tunnels for High Speed Trains.Faculdade de Ciências e Tecnologia da Universidade de Coimbra (FCT-UC

Numerical analysis of the Venda Nova II powerhouse complex

In the North of Portugal a hydroelectric scheme called Venda Nova II was recently built in order to optimize the resources of the reservoirs created by Venda Nova and Salamonde dams. The scheme, almost fully composed by underground structures and built in a predominantly granite rock mass, include several tunnels with a total length of about 7.5km, inclined and vertical shafts with a total length of 750m and two caverns which compose the powerhouse complex. The complex consists of two caverns interconnected by two galleries at a dept of about 350m. For this complex, 2D and 3D numerical models were developed considering the different construction stages. The geomechanical parameters of the granite formation for the numerical models were obtained using GEOPAT. This software is a knowledge based system which allows obtaining geomechanical parameters for underground structures modelling in granite formations. The 2D model was developed in the Phases2 software while the 3D model in FLAC3D. In this paper results of these models are analysed. Some comparisons are carried out between the models results and the monitored data. The numerical results show in general a good agreement with the monitored ones.Fundação para a Ciência e a Tecnologia (FCT) - projecto POCI/ECM/57495/2004 - Geotechnical Risk in Tunnels for High Speed Trains

Inverse analysis on two geotechnical works : a tunnel and a cavern

One of the major difficulties for geotechnical engineers during project phase is to estimate in a reliable way the mechanical parameters values of the adopted constitutive model. In project phase, they can be evaluated by laboratory and in situ tests. But, these tests lead to uncertainties due to the soil reworking and to local character of the test which is not representative of the soil mass. Moreover for in situ tests interpretation difficulties exist due to the non homogeneous character of the strain and stress fields applied to the soil mass. In order to reduce these uncertainties, geotechnical engineers can use inverse analysis processes during construction. This article shows the application of two of these processes (a deterministic and a probabilistic method) on convergence leveling measurements realized during the excavation of the Bois de Peu tunnel (France). Moreover, these two processes are also applied on displacements measured by inclinometers during the excavation of the hydroelectric powerhouse cavern Venda Nova II (Portugal). The two inverse analysis methods are coupled with two geotechnical software (CESAR-LCPC and FLAC3D) to identify soil parameters. Numerical and experimental results are compared.(undefined

Random Field and Random Anisotropy Effects in Defect-Free Three-Dimensional XY Models

Monte Carlo simulations have been used to study a vortex-free XY ferromagnet with a random field or a random anisotropy on simple cubic lattices. In the random field case, which can be related to a charge-density wave pinned by random point defects, it is found that long-range order is destroyed even for weak randomness. In the random anisotropy case, which can be related to a randomly pinned spin-density wave, the long-range order is not destroyed and the correlation length is finite. In both cases there are many local minima of the free energy separated by high entropy barriers. Our results for the random field case are consistent with the existence of a Bragg glass phase of the type discussed by Emig, Bogner and Nattermann.Comment: 10 pages, including 2 figures, extensively revise

Predictability in a highly stochastic system: final size of measles epidemics in small populations.

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.A standard assumption in the modelling of epidemic dynamics is that the population of interest is well mixed, and that no clusters of metapopulations exist. The well-known and oft-used SIR model, arguably the most important compartmental model in theoretical epidemiology, assumes that the disease being modelled is strongly immunizing, directly transmitted and has a well-defined period of infection, in addition to these population mixing assumptions. Childhood infections, such as measles, are prime examples of diseases that fit the SIR-like mechanism. These infections have been well studied for many systems with large, well-mixed populations with endemic infection. Here, we consider a setting where populations are small and isolated. The dynamics of infection are driven by stochastic extinction-recolonization events, producing large, sudden and short-lived epidemics before rapidly dying out from a lack of susceptible hosts. Using a TSIR model, we fit prevaccination measles incidence and demographic data in Bornholm, the Faroe Islands and four districts of Iceland, between 1901 and 1965. The datasets for each of these countries suffer from different levels of data heterogeneity and sparsity. We explore the potential for prediction of this model: given historical incidence data and up-to-date demographic information, and knowing that a new epidemic has just begun, can we predict how large it will be? We show that, despite a lack of significant seasonality in the incidence of measles cases, and potentially severe heterogeneity at the population level, we are able to estimate the size of upcoming epidemics, conditioned on the first time step, to within reasonable confidence. Our results have potential implications for possible control measures for the early stages of new epidemics in small populations.US Department of Homeland Security HSHQDC-12-C-00058 Eunice Kennedy Shriver National Institute of Child Health and Human Development 5R24HD047879 National Institutes of Health 5T32HD007163 Bill and Melinda Gates Foundation RAPIDD program of the Science and Technology Directorate, Department of Homeland Security Fogarty International Center, National Institutes of Healt

Fermi Surface as the Driving Mechanism for Helical Antiferromagnetic Ordering in Gd-Y Alloys

The first direct experimental evidence for the Fermi surface (FS) driving the helical antiferromagnetic ordering in a gadolinium-yttrium alloy is reported. The presence of a FS sheet capable of nesting is revealed, and the nesting vector associated with the sheet is found to be in excellent agreement with the periodicity of the helical ordering.Comment: 4 pages, 4 figure

Modeling oscillatory Microtubule--Polymerization

Polymerization of microtubules is ubiquitous in biological cells and under certain conditions it becomes oscillatory in time. Here simple reaction models are analyzed that capture such oscillations as well as the length distribution of microtubules. We assume reaction conditions that are stationary over many oscillation periods, and it is a Hopf bifurcation that leads to a persistent oscillatory microtubule polymerization in these models. Analytical expressions are derived for the threshold of the bifurcation and the oscillation frequency in terms of reaction rates as well as typical trends of their parameter dependence are presented. Both, a catastrophe rate that depends on the density of {\it guanosine triphosphate} (GTP) liganded tubulin dimers and a delay reaction, such as the depolymerization of shrinking microtubules or the decay of oligomers, support oscillations. For a tubulin dimer concentration below the threshold oscillatory microtubule polymerization occurs transiently on the route to a stationary state, as shown by numerical solutions of the model equations. Close to threshold a so--called amplitude equation is derived and it is shown that the bifurcation to microtubule oscillations is supercritical.Comment: 21 pages and 12 figure

Erratum to: Comparative assessment of image quality for coronary CT angiography with iobitridol and two contrast agents with higher iodine concentrations: iopromide and iomeprol. A multicentre randomized double-blind trial

Unfortunately, there is amistake in the section Results, Clinical safety. While the text states that “no severe AEs were reported”, in fact one severe AE was reported in the iomeprol group (one severe injection site pain assessed as possibly related to contrast agent), as shown in Table 5. In addition, the name of the author Jean-François Paul was rendered incorrectly in the original publication but has since been corrected. The authors apologize for these mistakes

Measurement of double-differential cross sections for top quark pair production in pp collisions at [Formula: see text][Formula: see text] and impact on parton distribution functions.

Normalized double-differential cross sections for top quark pair ([Formula: see text]) production are measured in pp collisions at a centre-of-mass energy of 8[Formula: see text] with the CMS experiment at the LHC. The analyzed data correspond to an integrated luminosity of 19.7[Formula: see text]. The measurement is performed in the dilepton [Formula: see text] final state. The [Formula: see text] cross section is determined as a function of various pairs of observables characterizing the kinematics of the top quark and [Formula: see text] system. The data are compared to calculations using perturbative quantum chromodynamics at next-to-leading and approximate next-to-next-to-leading orders. They are also compared to predictions of Monte Carlo event generators that complement fixed-order computations with parton showers, hadronization, and multiple-parton interactions. Overall agreement is observed with the predictions, which is improved when the latest global sets of proton parton distribution functions are used. The inclusion of the measured [Formula: see text] cross sections in a fit of parametrized parton distribution functions is shown to have significant impact on the gluon distribution