Movements Induced by Tunneling With an Epb Machine in over Consolidated Soils: Compans Monitoring Section of Toulouse Subway Line B

A part of Toulouse’s underground line B has been excavated by a 7.8 meters diameter earth-pressure balance machine. A comprehensive monitoring section has been installed in the Compans garden at a point where the tunnel cover is 12.8-meter and is running through overconsolidated clayey molasses underlying a 6.8 meters layer of made ground and gravels. The monitoring devices give full information on the ground movements above the tunnel and on deformations of the tunnel lining. Vertical movements are measured by 5 multipoint borehole extensometers with automatic data acquisition (every 5 seconds when the TBM crosses the monitoring section). At the end of each excavation phase, a high precision levelling of the borehole extensometer heads is performed in order to determine the total vertical displacements. Horizontal movements are measured by 3 inclinometers, one in the axis of the tunnel and the others on its sides, 2.3 meters away from the tunnel extrados. One of these inclinometers is 42 m long, i.e. 21.8 m below the level of the tunnel invert. The induced horizontal strains at ground level are measured by an invar thread in both longitudinal and transverse directions. Measurements show a specific behaviour of the soil due to its overconsolidated character (K0 greater than 1.5): even though the magnitude of the displacements is limited to a few millimeters, horizontal convergent movements are observed at the level of the tunnel axis while 3 to 4 times smaller heave is measured at ground surface (associated with horizontal extensions). Excavation parameters are automatically recorded and give information on the variation of the torque on the cutting wheel, the advancement rate, the confining pressure, the injection of annular void between soil and the concrete tunnel lining… This paper presents the results of the different monitoring devices and the possible correlations with the tunnel excavation parameters recorded by the TBM

Collapses of underground cavities and soil-structure interactions : experimental and numerical models

International audienceThe great subsidences result from the collapses of underground cavities man-made (mines or careers) or formed naturally by water flow in soluble solid masses of rocks (limestone, gypsum). Their impact on the existing structures standing on the surface is generally very important as show the recent examples of Auboué (1996), Moutiers (1997) and Roncourt (1999) which damaged more than five hundred buildings and the sinkhole on building site of METEOR subway in 2003. It is thus necessary to forecast the movements of the soil surface (subsidence and horizontal deformation) resulting from these phenomena and especially to determine the impact that may have the presence of structures on the form and the amplitude of these movements. The current practice to forecast the effects on the structures consists in determining the movements caused by the subsidence of the cavity without the building (in greenfield) then to use these results to check the capacity of the structure to resist the phenomenon. This approach can largely underestimate or over-estimate the generated loading, which in both cases has negative impacts (risk remaining for the structure or overcost of project in the other hand). In the present communication, soil-structure interaction during a sinkhole phenomenon is studied by a dual approach using a physical model and a numerical method. First of all, the physical model will use the bidimensionnal Schneebeli material in a small-scale model allowing fully controlled tests. The Schneebeli material is modified in order to allow the presence of cohesion. The soil mass of great dimensions (2m width for 1m height) makes it possible to represent the happening of a sinkhole with a scale factor of 1/40. The use of a building model will allow us to shed some light on the soil-structure interaction during the sinkhole. Thereafter we will set a numerical model using a coupled approach betwen finite difference and discrete element (FLAC2D – PFC2D coupled computations). This will allow us to study more easier different case of parameters : the size of the cavity, the thickness of the roof over the cavity, the position of the structure compared to the cavity, etc ..

A New International Database on Case Histories of Monitored Construction of Tunnels and Deep Excavations

The prototype of a new database for case histories of monitored construction of tunnels and deep excavations is presented in this paper. The basic requirements for this database have been established by the members of the Technical Committee TC28 of the International Society for Soil Mechanics and Geotechnical Engineering. It is based on the Content Management System (CMS) Typo3. The resulting structure is flexible, the data being mirrored on sites managed by each participant providing data. It uses a web interface where the user can navigate and access to the data via an indexed search engine. Some very basic and brief standard forms describe the type of work, the geotechnical context and the data available. The monitoring data are organized according to formats chosen by each of the participants. Guidelines and minimal rules have also been proposed in order to ensure that the data can be actually used. Nevertheless, the rules concerning availability/accessibility of the data outside the TC28 partners involved in the creation of the database still need to be discusse

A Stochastic Model to Measure Patient Effects Stemming from Hospital-Acquired Infections

We introduce a Markov chain model to represent a patient's path in terms of the number and type of infections sjhe may have acquired during a hospitalization period. The model allows for categories of patient diagnoses, surgery, the four major types of nosocomial (hospital-acquired) infections and discharqe or death. Data from a national medical records survey including 58,647 patients enable us to estimate transition probabilities and, ultimately, perform statistical tests of fit, including a validation test. Novel parameterizations (functions of the transition matrix) are introduced to answer research questions on timedependent infection rates, time to discharge or death as a function of patient characteristics at admission"and conditional infection rates reflecting intervening variables (e.g., surgery)

Impact des modèles de comportement sur la modélisation des ouvrages souterrains

La prédiction des tassements en surface étant un élément clé lors de l'exécution des travaux souterrains en milieu urbain, il est donc nécessaire d'utiliser des lois de comportement adaptées au calcul des ouvrages géotechniques en phase de service. Dans cet article, des modèles de comportement à différents niveaux de complexité sur des argiles surconsolidées sont mis en oeuvre. L'étude ne repose pas sur un chantier réel mais les paramètres mécaniques sont déduits d'essais triaxiaux puis utilisés pour la modélisation du creusement d'un tunnel peu profond en déformations planes. L'impact des modèles de comportement est ainsi mis en évidence sur les déplacements au sein du massif

Repeat prostate biopsy strategies after initial negative biopsy: meta-regression comparing cancer detection of transperineal, transrectal saturation and MRI guided biopsy.

INTRODUCTION: There is no consensus on how to investigate men with negative transrectal ultrasound guided prostate biopsy (TRUS-B) but ongoing suspicion of cancer. Three strategies used are transperineal (TP-B), transrectal saturation (TS-B) and MRI-guided biopsy (MRI-B). We compared cancer yields of these strategies. METHODS: Papers were identified by search of Pubmed, Embase and Ovid Medline. Included studies investigated biopsy diagnostic yield in men with at least one negative TRUS-B and ongoing suspicion of prostate cancer. Data including age, PSA, number of previous biopsy episodes, number of cores at re-biopsy, cancer yield, and Gleason score of detected cancers were extracted. Meta-regression analyses were used to analyse the data. RESULTS: Forty-six studies were included; 12 of TS-B, 14 of TP-B, and 20 of MRI-B, representing 4,657 patients. Mean patient age, PSA and number of previous biopsy episodes were similar between the strategies. The mean number of biopsy cores obtained by TP-B and TS-B were greater than MRI-B. Cancer detection rates were 30·0%, 36·8%, and 37·6% for TS-B, TP-B, and MRI-B respectively. Meta-regression analysis showed that MRI-B had significantly higher cancer detection than TS-B. There were no significant differences however between MRI-B and TP-B, or TP-B and TS-B. In a sensitivity analysis incorporating number of previous biopsy episodes (36 studies) the difference between MRI-B and TP-B was not maintained resulting in no significant difference in cancer detection between the groups. There were no significant differences in median Gleason scores detected comparing the three strategies. CONCLUSIONS: In the re-biopsy setting, it is unclear which strategy offers the highest cancer detection rate. MRI-B may potentially detect more prostate cancers than other modalities and can achieve this with fewer biopsy cores. However, well-designed prospective studies with standardised outcome measures are needed to accurately compare modalities and define an optimum re-biopsy approach

Absence of bimodal peak spacing distribution in the Coulomb blockade regime

Using exact diagonalization numerical methods, as well as analytical arguments, we show that for the typical electron densities in chaotic and disordered dots the peak spacing distribution is not bimodal, but rather Gaussian. This is in agreement with the experimental observations. We attribute this behavior to the tendency of an even number of electrons to gain on-site interaction energy by removing the spin degeneracy. Thus, the dot is predicted to show a non trivial electron number dependent spin polarization. Experimental test of this hypothesis based on the spin polarization measurements are proposed.Comment: 13 pages, 3 figures, accepted for publication in PRL - a few small change

Large greenhouse gas savings due to changes in the post-Soviet food systems

As the global food system contributes significantly to global greenhouse gas (GHG) emissions, understanding the sources of GHG emissions embodied in different components of food systems is important. The collapse of the Soviet Union triggered a massive restructuring of the domestic food systems, namely declining consumption of animal products, cropland abandonment, and a major restructuring of agricultural trade. However, how these complex changes have affected global GHG emissions is uncertain. Here, we quantified the net GHG emissions associated with changes in the former Soviet Union's food systems. Changes in food production, consumption, and trade together resulted in a net emissions reduction of 7.61 Gt carbon dioxide equivalents from 1992 to 2011. For comparison, this corresponds to one quarter of the CO2 emissions from deforestation in Latin America from 1991 to 2011. The key drivers of the emissions reductions were the decreasing beef consumption in the 1990s, increasing beef imports after 2000, mainly from South America, and carbon sequestration in soils on abandoned cropland. Ongoing transformations of the food systems in the former Soviet Union, however, suggest emissions will likely rebound. The results highlight the importance of considering agricultural production, land-use change, trade, and consumption when assessing countries emissions portfolios. Moreover, we demonstrated how emissions reductions that originate from a reduction in the extent and intensity of agricultural production can be compromised by increasing emissions embodied in rising imports of agricultural commodities.Volkswagen Foundation (BALTRAK)the German Federal Ministry of Food and Agriculture (BMEL) (GERUKA)The Swedish Research Council FormasThe Russian Foundation for Basic ResearchRussian Government Program of Competitive Growth of Kazan Federal UniversityEuropean Research Council (ERC)Peer Reviewe

Statistics of Coulomb Blockade Peak Spacings within the Hartree-Fock Approximation

We study the effect of electronic interactions on the addition spectra and on the energy level distributions of two-dimensional quantum dots with weak disorder using the self-consistent Hartree-Fock approximation for spinless electrons. We show that the distribution of the conductance peak spacings is Gaussian with large fluctuations that exceed, in agreement with experiments, the mean level spacing of the non-interacting system. We analyze this distribution on the basis of Koopmans' theorem. We show furthermore that the occupied and unoccupied Hartree-Fock levels exhibit Wigner-Dyson statistics.Comment: 5 pages, 2 figures, submitted for publicatio

Increasing impacts of land use on biodiversity and carbon sequestration driven by population and economic growth

Biodiversity and ecosystem service losses driven by land-use change are expected to intensify as a growing and more affluent global population requires more agricultural and forestry products, and teleconnections in the global economy lead to increasing remote environmental responsibility. By combining global biophysical and economic models, we show that, between the years 2000 and 2011, overall population and economic growth resulted in increasing total impacts on bird diversity and carbon sequestration globally, despite a reduction of land-use impacts per unit of gross domestic product (GDP). The exceptions were North America and Western Europe, where there was a reduction of forestry and agriculture impacts on nature accentuated by the 2007-2008 financial crisis. Biodiversity losses occurred predominantly in Central and Southern America, Africa and Asia with international trade an important and growing driver. In 2011, 33% of Central and Southern America and 26% of Africa's biodiversity impacts were driven by consumption in other world regions. Overall, cattle farming is the major driver of biodiversity loss, but oil seed production showed the largest increases in biodiversity impacts. Forestry activities exerted the highest impact on carbon sequestration, and also showed the largest increase in the 2000-2011 period. Our results suggest that to address the biodiversity crisis, governments should take an equitable approach recognizing remote responsibility, and promote a shift of economic development towards activities with low biodiversity impacts