Aging of Sand – a Continuing Enigma?

Sand aging, a process during which the engineering properties of clean sands such as stiffness, penetration resistance and liquefaction resistance may exhibit considerable improvement over periods of only weeks to months after deposition and/or densification by different ground improvement processes, has been shown over the past 30 years to be of considerable practical importance. Numerous examples from a range of projects are presented. Chemical, physical-mechanical, and microbiological processes are examined relative to their adequacy for explaining the observed behavior. Although chemical precipitation-cementation reactions had initially been considered a primary cause, the evidence clearly favors a secondary compression-like process during which particle rearrangements and internal interparticle stress changes and redistributions among groups of particles occur, accompanied by only small volumetric compressions. Information about the rate and magnitude of property changes during aging is summarized, and it is seen that there is considerable variability, dependent on the sand type, its initial state, applied stress conditions, and the specific property being measured. Thus, while the case history information may provide useful guidance about how much property change there will be due to aging and how fast it may occur, each case should be evaluated separately by means of field measurements. Further improvement in the understanding and quantification of sand aging may be possible using rate process and discrete element analysis methods

Computational Fluid Dynamics Simulation and Optimization of 69-Degree-Delta Wing Model in Supersonic Flow

The Computational Fluid Dynamics simulation and optimization of a 69-degree-deltawing model in a supersonic flow condition. The steady compressible Reynolds Averaged NavierStokes (RANS) equation using the inviscid Euler equations will be solved using the flow solver ANSYS Fluent. The CFD simulations will be compared to experimental and prior results before optimization begins. After simulation results compare well with AIAA sonic boom workshops provided data, a genetic algorithm will be created to optimize the deltawing to minimize the pressure disturbance [1]. The study of temperature effects on the pressure disturbance will also be considered using the sBOOM code provided by NASA Langley Research Cente

Comparison of Energies Required to Densify Liquefiable Soil

The objective of the study presented herein is to compare the energy required to densify loose, liquefiable sand by various techniques and the energy required to liquefy the soil by earthquake shaking. The states-of-practice for performing remedial ground densification and evaluating earthquake liquefaction potential of loose saturated sands have evolved relatively independently of each other. This is in spite of the fact that the inducement of liquefaction is typically requisite for remedial ground densification of sands. Using the energy required to induce liquefaction as a common metric, simple calculations are presented for estimating the mechanical energy required to densify a unit volume of clean, loose, saturated sand using deep dynamic compaction, vibrocompaction, and explosive compaction. These computed energies are compared with that required to induce liquefaction during an earthquake per the Green- Mitchell energy based liquefaction evaluation procedure. The comparison highlights the importance of the efficiency of the process by which the energy is imparted to the soil and the importance of the mode of dissipation of the imparted energy (e.g., breaking down of initial soil structure, ramming soil particles into denser packing, and/or radiating away from the treatment zone). Additionally, the comparison lays the groundwork for incorporating the vast knowledge from fundamental studies on earthquake induced liquefaction into design procedures for remedial ground densification

The Kettleman Hills Landfill Failure: A Retrospective View of the Failure Investigations and Lessons Learned

The sliding stability failure of the Kettleman Hills waste landfill focused attention on several issues related to the safe design and filling of waste repositories, including low strengths between geosynthetic material interfaces in composite liner systems and low interface strength between compacted clay and smooth geomembranes. Waste placement plans must be carefully developed to insure an adequate factor of safety against sliding at all stages of filling. Because of assumptions and uncertainties that remained following the initial failure investigation, model tests, at a scale of 1:150, were done. These tests reproduced the field failure very well and provided insights into the failure mechanisms. A three-dimensional method for stability analysis gave results in close agreement with field observations and the results of a subsequent detailed failure investigation done by others (Byrne et al., 1992). Those special cases of landfill geometry and liner properties for which the 3D stability may be more critical than that computed using usual 2D methods of analysis could then be determined

INCOME, WEALTH, AND THE ECONOMIC WELL-BEING OF FARM HOUSEHOLDS

Agricultural policy is rooted in the 1930s notion that providing transfers of money to the farm sector translates into increased economic well-being of farm families. This report shows that changes in income for the farm sector or for any particular group of farm businesses do not necessarily reflect changes confronting farm households. Farm households draw income from various sources, including off-farm work, other businesses operated, and increasingly nonfarm investments. Likewise, focus on a single indicator of well-being, like income, overlooks other indicators such as the wealth held by the household and the level of consumption expenditures for health care, food, housing, and other items. Using an expanded definition of economic well-being, we show that farm households as a whole are relatively better off than the average U.S. household, but that about 6 percent remain economically disadvantaged relative to the rest of the population.Consumption, farm households, income, wealth, well-being, off-farm employment, Consumer/Household Economics,

A preliminary checklist of fungi at the Boston Harbor Islands

Between December 2012 and May 2017, we conducted a fungal inventory at the Boston Harbor Islands National Recreation Area (BHI) in Massachusetts. We extensively sampled 4 sites (Grape Island, Peddocks Island, Thompson Island, and World's End peninsula) and occasionally visited 4 others for sampling (Calf Island, Great Brewster Island, Slate Island, and Webb Memorial State Park). We made over 900 collections, of which 313 have been identified. The survey yielded 172 species in 123 genera, 62 families, 24 orders, 11 classes, and 2 phyla. We report 4 species as new, but not formally described, in the genera Orbilia, Resupinatus, and Xylaria. Another collection in the genus Lactarius may be new to science, but further morphological and molecular work is needed to confirm this conclusion. Additionally, Orbilia aprilis is a new report for North America, Proliferodiscus earoleucus represents only the second report for the US, and Chrysosporium sulfureum, a common fungus of some cheeses, was discovered on woodlice (Crustacea: Malacostraca: Isopoda: Oniscidea). We discuss our findings in the light of DNA-based identifications using the ITS ribosomal DNA region, including the advantages and disadvantages of this approach, and stress the need for biodiversity studies in urbanized areas during all seasons

A preliminary assessment of water partitioning and ecohydrological coupling in northern headwaters using stable isotopes and conceptual runoff models

Funded by European Research Council ERC. Grant Number: GA 335910 VEWA Swedish Science Foundation (SITES) Future Forest Formas (ForWater) SKB the Kempe foundation Environment Canada the Garfield Weston Foundation the Natural Sciences and Engineering Research Council of Canada (NSERC) the Northwest Territories Cumulative Impacts Monitoring ProgramPeer reviewedPublisher PD

Similar strains of Burkholderia spp. nodulate the South African invasive legume Dipogon lignosus in New Zealand and Australian soils

Brazil and South Africa are centres of diversity of Burkholderia ssp. that nodulate legumes (Gyaneschwar et al, 2011; Beukes et al. 2013). The nod gene sequence of Burkholderia spp, capable of nodulating South Africa plants are clearly separated from those of Burkholderia spp. shown to nodulate South American plants. Where tested, the South African strains did not nodulate South American plants nodulated by Burkholderia spp. (Gyaneschwar et al. 2011)