334 research outputs found
ADECO full-face tunnel excavation of two 260m2 tubes in clays with sub-horizontal jet-grouting under minimal urban cover
No full textSome properties of a random set approximation to upper and lower distribution functions
No full textAbstractInformation on an uncertain real variable is oftentimes conveyed using upper and lower distribution functions, which define a credal set, M. The paper explores the properties of a random set (random interval) approximation, R, to the upper and lower distribution functions carried out using the outer discretization method (ODM) introduced by the author as a generalization to an algorithm proposed in Williamson and Downs [R.C. Williamson, T. Downs, Probabilistic arithmetic. i. Numerical methods for calculating convolutions and dependency bounds, Int. J. Approx. Reason. 4 (1990) 89–158]. It is shown that probability bounds calculated using the ODM random sets, R, always contain the probability bounds calculated using M. This result holds even in the multivariate case (when each marginal is ODM discretized into a random set, R) regardless of the concept of dependence or independence adopted. The bound inclusion is also true for the image of a function defined on those variables. Finer discretizations of the original credal sets yield tighter or equal probability bounds. Since the ODM yields a random set, R, the information can be modeled either using probability measures of the measurable selections or the credal set of the belief and plausibility of R. It is proven that both models yield the same probability bounds and that the Choquet integrals of the belief and plausibility of R are the inferior and superior, respectively, of the expectations calculated using the measurable selections. However, the probabilistic information conveyed by the measurable selections may be more restrictive than the information contained in the credal set of the belief and plausibility of R
Rock tunnel groundwater prediction in a simulated rock fracture network
No full textChen and Tonon (2011) showed that groundwater inflows in rock tunnels typically concentrate in narrow zones where conducting fractures cluster together. A geostatistical methodology was proposed to simulate clustered fractures. In this paper, the resulting discrete fracture network is generated and simplified. An existing analytical-numerical method (Long et al., 1985) for steady fluid flow in three-dimensional, random networks of fractures is improved and used to simulate groundwater flow and predict groundwater inflow into tunnels. Several synthetic tunnel cases and an actual case history at the South Cobb Tunnel Project (GA) are used to validate the flow analysis. It is found that flow concentration can be reproduced by using the proposed technique in the simulated discrete fracture network
Tunneling in difficult conditions: The squeezing case
No full textThis paper deals with tunneling in squeezing conditions, and highlights different ways proposed to successfully drive a tunnel in such difficult conditions. © 2012 American Society of Civil Engineers
Does elastic anisotropy significantly affect a tunnel's plane strain behavior?
No full textRock masses are anisotropic because their properties depend on the orientation considered. The diverging opinions in the literature on whether the elastic anisotropy of a rock mass significantly affects the plane strain behavior of a tunnel are contrasted. A two-dimensional parametric study is presented to answer the questions raised by the literature review. For a given premining state of stress, the stress field around a tunnel in an anisotropic rock mass is not significantly different from the stress field around a tunnel in an isotropic rock mass. For a given anisotropic rock mass, the stress and displacement fields, as well as slip zones, obtained under the hypothesis of no lateral strain are radically different from that obtained under the hypothesis of uniform premining state of stress. In the first case, the slip zones can penetrate more than two diameters into the rock mass, especially for vertical or inclined joints. In the second case, the slip zones extend for a maximum of half a tunnel diameter into the rock mass, regardless of rock mass anisotropy. Displacement vector magnitudes are highly influenced by the elastic anisotropy of the rock mass, even if the premining state of stress is fixed. For a given premining state of stress, slip zones around a tunnel are unaffected by the elastic anisotropy of the rock mass. The slip zones depend only on the orientation of the joints along which slippage can occur
ADECO as an alternative to NATM: 22 m wide, 14 m high, full face tunnel excavation in clays
No full textInteraction diagram and load effects for vertical pile groups with application to the AASHTO LRFD
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