Experimental and numerical investigation of footing behaviour on multi-layered rubber-reinforced soil

This paper describes the beneficial effects of multiple layers of rubber–sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM layers was granulated rubber, produced from waste tires. The optimum thickness of the RSM layer was determined to be approximately 0.4 times the footing diameter. By increasing the number of RSM layers, the bearing capacity of the foundation can be increased and the footing settlement reduced. The influence of the number of RSM layers on bearing capacity and settlement become almost insignificant beyond three layers of RSM, particularly at low settlement ratios. At a ratio of settlement to plate diameter of 4%, the values of bearing pressure for the installation with one, two, three and four layers of RSM were about 1.26, 1.47, 1.52 and 1.54 times greater, respectively, than that for the unreinforced installation. Layers of the RSM reduced the vertical stress transferred through the foundation depth by distributing the load over a wider area. For example, at an applied footing pressure of 560 kPa, the transferred pressure at a depth of 570 mm was about 58, 45 and 35% for one, two and three layers of RSM, respectively, compared to the transferred stress in the unreinforced bed. By numerical analysis, it was found that the presence of soil-rubber layers resulted in expansion of passive zones in the foundation due to the effectiveness of the confinement provided by the rubber inclusions, and this tends to make the bed deflect less. On the basis of this study, the concept of using multiple RSM layers has not only been shown to improve the performance of foundations under heavy loading, but also, the environmental impacts of waste tires are attenuated by re-using their rubber as part of a composite soil material in civil engineering works

Experimental study and numerical reproduction of self-weight consolidation behavior of thickened tailings

Abstract: Thickened tailings, defined as mineral wastes that behave as a non-Newtonian fluid, show a small yield stress and release a small amount of water following deposition. Thickening has become an increasingly used option in tailings management. This paper presents a detailed examination of gold mine thickened tailings undergoing self-weight consolidation, which is an important mechanism affecting soft soils immediately after deposition. Self-weight consolidation was evaluated using a column equipped with water pressure transmitters whereas a slurry consolidometer was employed to obtain the compressibility relationship under low vertical effective stresses. The piecewise-linear model CS2 was used to model the experimental self-weight consolidation test. This model proved very accurate in reproducing the observed behavior. Both the test results and the model results also confirmed the absence of sedimentation in the thickened tailings, which is in agreement with values reported in the literature related to similar materials

Fabrication and mechanical testing of a new sandwich structure with carbon fiber network core

The aim is the fabrication and mechanical testing of sandwich structures including a new core material known as fiber network sandwich materials. As fabrication norms for such a material do not exist as such, so the primary goal is to reproduce successfully fiber network sandwich specimens. Enhanced vibration testing diagnoses the quality of the fabrication process. These sandwich materials possess low structural strength as proved by the static tests (compression, bending), but the vibration test results give high damping values, making the material suitable for vibro-acoustic applications where structural strength is of secondary importance e.g., internal panelling of a helicopter

High pressure gas flow, storage, and displacement in fractured rock-Experimental setup development and application.

This paper presents the design, development, and application of a laboratory setup for the experimental investigations of gas flow and reactions in a fractured rock. The laboratory facility comprises (i) a high pressure manometric sorption apparatus, where equilibrium and kinetic phenomena of adsorption and desorption can be examined, (ii) a high pressure triaxial core flooding system where the chemical reactive transport properties or processes can be explored, and (iii) an ancillary system including pure and mixed gas supply and analysis units. Underground conditions, in terms of pore pressure, confining pressure, and temperature, can be replicated using the triaxial core flooding system developed for depths up to 2 km. Core flooding experiments can be conducted under a range of gas injection pressures up to 20 MPa and temperatures up to 338 K. Details of the design considerations and the specification for the critical measuring instruments are described. The newly developed laboratory facility has been applied to study the adsorption of N2, CH4, and CO2 relevant to applications in carbon sequestration in coal and enhanced coalbed methane recovery. Under a wide range of pressures, the flow of helium in a core sample was studied and the evolution of absolute permeability at different effective stress conditions has been investigated. A comprehensive set of high resolution data has been produced on anthracite coal samples from the South Wales coalfield, using the developed apparatus. The results of the applications provide improved insight into the high pressure flow and reaction of various gas species in the coal samples from the South Wales coalfield

UV Degradation of the Optical Properties of Acrylic for Neutrino and Dark Matter Experiments

UV-transmitting (UVT) acrylic is a commonly used light-propagating material in neutrino and dark matter detectors as it has low intrinsic radioactivity and exhibits low absorption in the detectors' light producing regions, from 350 nm to 500 nm. Degradation of optical transmittance in this region lowers light yields in the detector, which can affect energy reconstruction, resolution, and experimental sensitivities. We examine transmittance loss as a result of short- and long-term UV exposure for a variety of UVT acrylic samples from a number of acrylic manufacturers. Significant degradation peaking at 343 nm was observed in some UVT acrylics with as little as three hours of direct sunlight, while others exhibited softer degradation peaking at 310 nm over many days of exposure to sunlight. Based on their measured degradation results, safe time limits for indoor and outdoor UV exposure of UVT acrylic are formulated.Comment: 13 pages, 6 figures, 3 tables; To be submitted to Journal of Instrumentatio

Impact damage and CAI strength of a woven CFRP material with fire retardant properties

This paper presents the interrogation of low velocity impact and compression after impact test results on a woven fibre composite having a fire retardant, syntactic core, two phase epoxy matrix. The results of the study were to be utilized in a decision making process regarding the appropriateness of the material usage in question for a certain aerospace application. The epoxy matrix of the material system had dispersed black-pigmented particles with flame-retarding properties. Impact tests were performed at five impact energy levels. Two different laminate layup configurations were tested. Visual and C-Scan inspection were conducted, in order to observe the extent of the damage in the composite material. Compression tests were performed to study the residual strength after impact. Analytical formulation correlations with the test results presented opportunities for quantifying the interfacial fracture toughness resistance. Micro-graphs of the specimen's cross section were also produced in an effort to observe the fractured sections and characterise the various fracture mechanisms involved. The results exploitation in terms of design decision making are presented

Indentation Hardness Measurements at Macro-, Micro-, and Nanoscale: A Critical Overview

The Brinell, Vickers, Meyer, Rockwell, Shore, IHRD, Knoop, Buchholz, and nanoindentation methods used to measure the indentation hardness of materials at different scales are compared, and main issues and misconceptions in the understanding of these methods are comprehensively reviewed and discussed. Basic equations and parameters employed to calculate hardness are clearly explained, and the different international standards for each method are summarized. The limits for each scale are explored, and the different forms to calculate hardness in each method are compared and established. The influence of elasticity and plasticity of the material in each measurement method is reviewed, and the impact of the surface deformation around the indenter on hardness values is examined. The difficulties for practical conversions of hardness values measured by different methods are explained. Finally, main issues in the hardness interpretation at different scales are carefully discussed, like the influence of grain size in polycrystalline materials, indentation size effects at micro-and nanoscale, and the effect of the substrate when calculating thin films hardness. The paper improves the understanding of what hardness means and what hardness measurements imply at different scales.Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University ((Faculty Grant SFO Mat LiU) [2009 00971]</p

Effects of Redispersible Polymer Powder on Mechanical and Durability Properties of Preplaced Aggregate Concrete with Recycled Railway Ballast

The rapid-hardening method employing the injection of calcium sulfoaluminate (CSA) cement mortar into voids between preplaced ballast aggregates has recently emerged as a promising approach for the renovation of existing ballasted railway tracks to concrete tracks. This method typically involves the use of a redispersible polymer powder to enhance the durability of the resulting recycled aggregate concrete. However, the effects of the amount of polymer on the mechanical and durability properties of recycled ballast aggregate concrete were not clearly understood. In addition, the effects of the cleanness condition of ballast aggregates were never examined. This study aimed at investigating these two aspects through compression and flexure tests, shrinkage tests, freezing-thawing resistance tests, and optical microscopy. The results revealed that an increase in the amount of polymer generally decreased the compressive strength at the curing age of 28 days. However, the use of a higher polymer ratio enhanced the modulus of rupture, freezing-thawing resistance, and shrinkage resistance, likely because it improved the microstructure of the interfacial transition zones between recycled ballast aggregates and injected mortar. In addition, a higher cleanness level of ballast aggregates generally improved the mechanical and durability qualities of concrete

Thickness dependence of the resistivity of Platinum group metal thin films

We report on the thin film resistivity of several platinum-group metals (Ru, Pd, Ir, Pt). Platinum-group thin films show comparable or lower resistivities than Cu for film thicknesses below about 5\,nm due to a weaker thickness dependence of the resistivity. Based on experimentally determined mean linear distances between grain boundaries as well as ab initio calculations of the electron mean free path, the data for Ru, Ir, and Cu were modeled within the semiclassical Mayadas--Shatzkes model [Phys. Rev. B 1, 1382 (1970)] to assess the combined contributions of surface and grain boundary scattering to the resistivity. For Ru, the modeling results indicated that surface scattering was strongly dependent on the surrounding material with nearly specular scattering at interfaces with SiO2 or air but with diffuse scattering at interfaces with TaN. The dependence of the thin film resistivity on the mean free path is also discussed within the Mayadas--Shatzkes model in consideration of the experimental findings.Comment: 28 pages, 9 figure