Lightweight cellular concrete (LCC) is an aerated or foamed concrete where 25-80% of the concrete matrix consists of air voids. The high volume of air voids reduces the strength but significantly decreases the weight of the material, which has made it an attractive alternative to soil for retaining structure backfills. Though the use of LCC has increased, little research has been performed on the large-scale behavior of retaining structures containing LCC as backfill. This research test attempts to fill knowledge gaps found with regard to the use of LCC in a mechanically stabilized earth (MSE) wall with a trapezoidal or sliver fill by examining the nature of LCC strength criteria from large-scale failure, failure mechanisms, and failure criteria. A large-scale test box (10 ft. wide x 12 ft. long x 10 ft. high), surrounded by a steel resisting frame, was constructed and filled with a silty sand backfill soil in a 1:1 stair-stepped slope and an LCC sliver fill. The west-facing wall was a two-paneled MSE wall with 16 ribbed steel strip reinforcements running through the LCC backfill. The LCC was poured over three days in equal height lifts to ensure stability. A total of 64 sample cylinder molds and four split mold shear boxes were filled with LCC during placement to help identify LCC material properties, which included density, unconfined compressive strength (UCS), and shear strength. A surcharge test was performed on the large-scale test box six days after initial placement of the LCC due to the unanticipated high strength gain and density found within the placed LCC. Instrumentation collected data on displacement, shear plane, lateral wall pressure, and reinforcement strain throughout testing. Initially, four hydraulic jacks were used during surcharge testing to induce a uniform surcharge load to fail the sliver-fill MSE wall. The strength limit of the steel resisting frame was reached before failure, at which point the number of hydraulic jacks was switched to three for a more critical loading condition. The test was again terminated before complete failure when the steel resisting frame strength limit was met. Though failure was not completed, the sliver-fill MSE wall failure had initiated before testing was terminated at a surcharge load of 70 psi. Results identify the initiation of shear failure within the LCC at about 65 psi, with maximum lateral and axial displacements of about 0.5 in. and 1.2 in., respectively. The shear failure occurs at about 52% of the average UCS of 123 psi. An arcuate shear plane, contrary to the traditional bilinear MSE wall failure surface with inextensible reinforcements, was identified within the LCC backfill, which initiated from the toe of the MSE wall and ended about 8 ft. back from the top of the MSE wall, using lateral displacements from Sondex tube profilometers in the backfill.

Surface mesh generation is a critical component of the mesh generation process. The objective of the described effort was to determine if a combination of constrained Delaunay triangulation (for triangles), advancing front method (for quadrilaterals), curvature-based refinement, smoothing, and reconnection is a viable approach for discretizing a NURBS patch holding the boundary nodes fixed. The approach is significant when coupled with recently developed geometry specification that explicitly identifies common edges. This thesis describes the various techniques used to achieve the above objectives. Application of this approach to several representative geometries demonstrates that it is an effective alternative to traditional approaches.

No description available.

La zone de subduction entre les plaques Nazca et Amérique du Sud est une des régions les plus actives de notre planète. De grands tremblements de terre et tsunamis associés se produisent de façon récurrente presque tout au long de sa marge. Néanmoins, le segment de subduction au nord du Pérou (de lat.3oS à 9oS) est resté le seul segment sismiquement silencieux depuis les premières informations historiques sur les séismes qui remontent au XVème siècle. Avant les travaux présentés dans ce manuscrit, aucune information sur les processus accommodant la convergence de la plaque Nazca vers le continent Sud-Américain n’était disponible le long du segment de 1000km au nord Pérou et sud Equateur. Les techniques de géodésie spatiale, en particulier le GPS/GNSS, nous permettent de quantifier les mouvements à la surface de la plaque supérieure avec une précision millimétrique. Ces mesures, couplées à l'utilisation de modèles élastiques, nous permettent de déterminer le niveau du couplage intersismique le long de l'interface entre les plaques. Le but de ma thèse est d'étudier le cycle sismique et la déformation continentale le long de la zone de subduction du Pérou, avec un intérêt particulier pour son segment nord. Nous utilisons des mesures GPS acquises depuis 2008 dans le cadre d'un projet international (le projet Andes Du Nord, ANR- ADN). Le champ de vitesse GPS obtenu couvre l’ensemble de la marge de subduction péruvienne, avec des mesures dans la cordillère et dans une moindre mesure dans la région sub-Andine. L'analyse et la modélisation du champ de vitesse GPS ont permis d'obtenir les résultats suivants: Premièrement: nous mettons en évidence l'existence d'un nouveau domaine continental, que nous avons baptisé comme le sliver Inca et qui est en translation a une vitesse de 4-5 mm/an en direction sud-est par rapport au craton Sud Américain. Le sliver Inca s’étend tout le long de la marge péruvienne. / The Nazca/South American subduction zone is one of the most active regions on Earth. Large earthquakes and associated tsunamis occur recurrently almost all along its margin. Nevertheless, the ~1000 km long (from lat.2oS to 9oS) segment in northern Peru and southern Ecuador subduction has remained in relative seismic silence for at least the past five centuries. Before the work presented in this thesis, no information about the processes accommodating the convergence was available for this region and it was impossible to answer whether it could host a great Mw>8.5 earthquake in future or not. Nowadays, spatial geodesy, and more specifically GPS/GNSS enable us to quantify the surface displacement on the overriding plate with millimeter accuracy. Geodetic measurements together with the use of elastic models allow us to determine the amount of interseismic coupling at the plate interface. My thesis focuses on the seismic cycle and the continental deformation along the Peruvian subduction margin, with particular interest along its northern and central segments. We use GPS measurements acquired since 2008 in the frame of an international French-Peruvian- Ecuadorian project (the Andes Du Nord project, ADN). Our GPS velocity field covers the entire Peruvian subduction margin, with measurements in the Andean cordillera and part of the sub-Andean region. Modeling of GPS velocity field show the existence of a new tectonic microplate that we baptized as the Inca Sliver, which is in southeastward translation a rate of 4-5 mm/yr with respect to stable South America.

Image segmentation plays an important role in medical image analysis. Many segmentation algorithms exist. Most of them produce data which are more or less not suitable for further surface extraction and anatomical modeling of human tissues. In this thesis, a novel segmentation technique based on the 3D Delaunay triangulation is proposed. A modified variational tetrahedral meshing approach is used to adapt a tetrahedral mesh to the underlying CT volumetric data, so that image edges are well approximated in the mesh. In order to classify tetrahedra into regions/tissues whose characteristics are similar, three different clustering schemes are presented. Finally, several methods for improving quality of the mesh and its adaptation to the image structure are also discussed.

No description available.