Water Saturation Effects on the Brazilian Tensile Strength of Gypsum and Assessment of Cracking Processes Using High-Speed Video

This study investigates the water weakening effect on the tensile strength, as well as the fracturing behavior, of an artificially molded Hydrocal B-11 gypsum rock. Brazilian disc tests, with the aid of a high-speed video system to monitor and record the cracking processes, are conducted on dry and wet specimens to determine their tensile strengths. The dry specimens are oven-dried, while the wet specimens are prepared by soaking in water for 1, 3, and 10 weeks to achieve different levels of water content. The test results show that the tensile strength drops to nearly half of its dry value after being soaked in water for only 1 week. The tensile strength reduces only slightly further after the specimens have been immersed in water for 3 and 10 weeks. An analysis of the recorded high-speed footage shows that the primary crack initiates at the center as observed from the surface for the majority of the tested specimens. Most importantly, the cracking processes of dry and wet specimens are distinctly different with regard to the speed of crack propagation and the number of cracks developed.     

Antenna-coupled arrays of NbSi micro-bolometers

Microbolometers are at present the most sensitive detectors for mm and sub-mm Astronomy. They are in use in most of the present instruments in that bandwidth. We have developed filled arrays of NbSi-based planar antenna coupled microbolometers. The fabrication details are given, together with characterization of the NbSi thermometers and optical results. The optical performances are potentially good for ground-based mm-wave astronomy applications, while the overall detectors performances are limited by low-frequency excess noise in the thermometric NbSi high-impedance sensors (Anderson insulator).     

Near-well upscaling for three-phase flows

Large-scale flow models constructed using standard coarsening procedures may not accurately resolve detailed near-well effects. Such effects are often important to capture, however, as the interaction of the well with the formation can have a dominant impact on process performance. In this work, a near-well upscaling procedure, which provides three-phase well-block properties, is developed and tested. The overall approach represents an extension of a recently developed oil–gas upscaling procedure and entails the use of local well computations (over a region referred to as the local well model (LWM)) along with a gradient-based optimization procedure to minimize the mismatch between fine and coarse-scale well rates, for oil, gas, and water, over the LWM. The gradients required for the minimization are computed efficiently through solution of adjoint equations. The LWM boundary conditions are determined using an iterative local-global procedure. With this approach, pressures and saturations computed during a global coarse-scale simulation are interpolated onto LWM boundaries and then used as boundary conditions for the fine-scale LWM computations. In addition to extending the overall approach to the three-phase case, this work also introduces new treatments that provide improved accuracy in cases with significant flux from the gas cap into the well block. The near-well multiphase upscaling method is applied to heterogeneous reservoir models, with production from vertical and horizontal wells. Simulation results illustrate that the method is able to accurately capture key near-well effects and to provide predictions for component production rates that are in close agreement with reference fine-scale results. The level of accuracy of the procedure is shown to be significantly higher than that of a standard approach which uses only upscaled single-phase flow parameters.     

Le bassin stéphanien des Cévennes (Massif Central) : un exemple de relation entre sédimentation et tectonique extensive tardi-orogénique dans la chaîne varisque

Résumé

La nature syn-sédimentaire des failles bordières du bassin houiller stéphanien des Cévennes est mise en évidence par la distribution des dépôts conglomératiques et gréseux de cône alluvial au pied des paléoreliefs de socle. Elle est également attestée par les fortes variations d’épaisseur caractérisant les niveaux gréseux, silteux et de charbon se distribuant au centre des sous-bassins ainsi que par les directions centripètes d’apport sédimentaire.

A l’échelle du bassin, la nature extensive de la structuration syn-sédimentaire est mise en évidence par des failles normales d’orientation NW-SE, NE-SW et NNW-SSE, à fort pendage, structurant les sous-bassins en demi-graben à géométrie synclinale ou à configuration divergente. Dans le secteur SE du bassin de la Grand’Combe, les structures syn-sédimentaires extensives coexistent avec des plis précoces reliés à un décollement généralisé au niveau des couches de charbon « Sans Nom ».

L’intégration des données structurales et microtectoniques collectées dans les dépôts stéphaniens et dans le socle montre que la structuration syn-sédimentaire extensive du bassin stéphanien est associée au cours du temps à une rotation progressive antihoraire de la direction d’extension principale successivement NE-SW à NW-SE.

L’ensemble des données tectono-sédimentaires nous permet de proposer une nouvelle interprétation du bassin stéphanien des Cévennes dans le cadre de la tectonique extensive tardi- orogénique de la chaîne varisque. Cette interprétation est illustrée par un modèle de bassin extensif intégrant une structuration générale en demi-graben et une tectonique gravitaire locale. La tectonique gravitaire s’exprime par la mise en place de décollements superficiels en liaison avec la surrection du horst dissymétrique du Rouvergue, en position axiale dans le bassin.     

Geological aspects of marine slope stability,northwestern Gulf of Mexico

Abstract

The improvement of sensors such as various high‐resolution seismic and navigational systems and side‐scan sonar, of offshore shallow‐water drilling techniques, and of laboratory analyses has allowed the marine geologist to make more accurate identifications and maps of the distribution of numerous types of marine sediment instabilities, as well as to determine the mechanisms responsible for their occurrence. A large number of data on the continental shelf and upper continental slope off the modern delta of the Mississippi river have been compiled; these data will be used to document the major types of slope instabilities. The continental shelf and slope off the modern Mississippi river delta display various types of sediment instability. High rates of sedimentation (up to 80 m per century), weak, high‐water‐content clays, and differential weighting of clay sediments characterize this region. The major types of sediment instabilities that have been documented include (a) Peripheral slumping, with dimensions of slumps ranging from 200 to 1000 m; slumping often occurring in multiple stairstep arrangement; and downslope movement as high as 700 m per year. (b) Shallow diapiric intrusions, ranging in size from a few hundred meters to 2 km in diameter; vertical displacement ranging from 200 to 500 m; rate of sediment movement several meters per year; and intrusions caused by differential sediment loading, (c) Radial graben (tensional faulting), with widths from 50 to 500 m and lengths of several kilometers; both vertical and downslope lateral movements occurring; and downslope movements of surface material as much as 5 m per year common. (d) Circular collapse depressions, with diameters of depressions ranging from 50 to 500 m; topography of depression interiors, hummocky; and depressions possibly caused by dewatering or degassing of sediments under the influence of cyclic wave loading. (e) Surface mudflows, thick (often more than 35 m) masses of surface sediment flowage; often bounded by abrupt seaward slope; mudflows often extending laterally for distances in excess of 100 km; movement sporadic and lobate and rates of movement as much as several hundred meters per year; often being associated with extremely hummocky topography and mud volcanoes; and with extrusion of sediments the possible mechanism. (f) Shelf‐edge arcuate slumps, with large arcuate slumps displacing several hundred meters of sediment; slippage planes are commonly concave. Finally, (g) Various deep‐seated faults, with faults extending from deep horizons up to modern sediment surface; commonly being associated with abrupt scarps on the seafloor; numerous contemporaneous faults; and local slumping associated with fault scarps.     

The critical state and steady state of sand: A literature review

Abstract

The critical state and steady state theories are widely accepted for simulating the soil behavior and providing a basis for liquefaction evaluation and constitutive modeling. However, there was conflicting evidence regarding the critical state and steady state of sands in the last decades. In some cases, the critical state and steady state are taken to be identical and in others they differ significantly. Whether they are the same or not remain a hot academic debate to date. This paper provides a critical review on the origin and history of the critical state and steady state of sands, which identifies conflicting evidences and discusses the influencing factors on the existence and uniqueness of critical state and steady state. Based on a critical review of literature, it is concluded that the steady state concept is a refinement of the critical state concept and the uniqueness of the critical state and steady state was affirmed. Special care should be paid in the laboratory techniques in order to accurately measure the critical state and steady state due to the numerous influencing factors of them.     

Development of risk matrices for evaluating climatic change responses of forested habitats

We present an approach to assess and compare risk from climate change among multiple species through a risk matrix, in which managers can quickly prioritize for species that need to have strategies developed, evaluated further, or watched. We base the matrix upon earlier work towards the National Climate Assessment for potential damage to infrastructures from climate change. Risk is defined here as the product of the likelihood of an event occurring and the consequences or impact of that event. In the context of species habitats, the likelihood component is related to the potential changes in suitable habitat modeled at various times during this century. Consequences are related to the adaptability of the species to cope with the changes, especially the increasing intensity and/or frequency of disturbance events that are projected. We derived consequence scores from nine biological and 12 disturbance characteristics that were pulled from literature for each species. All data were generated from an atlas of climate change for 134 trees of the eastern United States (www.nrs.fs.fed.us/atlas). We show examples which depict a wide range of risk for tree species of northern Wisconsin, including species that may gain substantial habitat as well as lose substantial habitat, both of which will require the development of strategies to help the ecosystems adapt to such changes.     

Effective intellectual property protection of traditional knowledge of plants and their uses: an example from Australia

Intellectual property rights (IPR) to traditional knowledge (TK) about Australian native plants could justifiably be described as a birthright of Australian Aboriginal people. However, as is generally the case throughout the world, this right is currently not protected under Australian law. A case study is presented describing the approach that was taken to protecting the plant knowledge rights of traditional knowledge (TK) holders who participated in research at Titjikala, central Australia. From a review of international efforts aimed at developing a legal regime for protection of traditional knowledge (TK) intellectual property rights (IPR), we found that protecting traditional knowledge (TK) of plants and their uses is most likely to be achieved through the development of effective protocols for preserving and recording traditional knowledge (TK) and the use of contract law in commercial applications of that knowledge. The process of negotiating a research agreement between the research organisations and the community is described. Relationship building and a partnership approach based on trust and mutual respect were found to be of fundamental importance. The negotiated agreement ensures that the community has an equal share to research partners in any benefits that might arise from commercialisation of research findings. The approach to benefit sharing developed in this project has application in other research projects in which the sharing of traditional knowledge (TK) is a fundamental and essential component of the research process.