scholarly journals Backward erosion testing : Magnolia Levee

2021 ◽  
Author(s):  
Axel Montalvo-Bartolomei ◽  
Bryant Robbins ◽  
Erica Medley ◽  
Benjamin Breland
Keyword(s):  
Bulk Sample ◽  
Depositional Environments ◽  
Horizontal Gradient ◽  
Erosion Testing ◽  
Grain Size Distributions ◽  
Glacial Outwash ◽  
Coefficient Of Uniformity ◽  
Backward Erosion Piping ◽  
Sand And Gravel ◽  
A Site

Using a confined flume device, an experimental study investigated the critical horizontal gradient of soils obtained from a site identified as potentially vulnerable to backward erosion piping (BEP). Tests were conducted on glacial outwash material obtained from a sand and gravel quarry in the vicinity of Magnolia Levee in the community of Magnolia, OH. The two bulk samples collected from the quarry had similar grain-size distributions, grain roundness, and depositional environments as the foundation materials beneath the levee. Samples were prepared at various densities and subjected to gradual increases of flow in a wooden flume with an acrylic top until BEP was observed. The critical average horizontal gradient ranged from 0.21 to 0.30 for a bulk sample with a coefficient of uniformity of 1.6, while tests conducted on a bulk sample with a coefficient of uniformity of 2.5 yielded critical average horizontal gradients of 0.31 to 0.36. The critical average gradients measured during these tests compared favorably to values in the literature after applying adjustments according to Schmertmann’s method.

In situmonitoring of phase transformation microstructures at Earth's mantle pressure and temperature using multi-grain XRD

2015 ◽  
Vol 48 (5) ◽  
pp. 1346-1354 ◽  
Author(s):  
Angelika Dorothea Rosa ◽  
Nadège Hilairet ◽  
Sujoy Ghosh ◽  
Gaston Garbarino ◽  
Jeroen Jacobs ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Bulk Sample ◽  
Ex Situ ◽  
Orientation Relations ◽  
Grain Size Distributions ◽  
Geophysical Processes ◽  
Transformation Mechanisms ◽  
Diamond Anvil ◽  
Dependent Growth ◽  
Individual Grains

Microstructures govern the mechanical properties of materials and change dramatically during phase transformations. A detailed understanding of microstructures at different stages of a transformation is important for the design of new materials and for constraining geophysical processes. However, experimental studies of transformation microstructures at the grain scale have been mostly based onex situobservations of quenched products, which are difficult to correlate with bulk sample properties and transformation kinetics. Here, it is shown how multi-grain crystallography on polycrystalline samples, combined with a resistively heated diamond anvil cell, can be applied to investigate the microstructural properties of a material undergoing a phase transitionin situat high pressure and high temperature. This approach allows the extraction of the crystallographic parameters and orientations of several hundreds of grains inside a transforming sample. Important bulk information on grain size distributions and orientation relations between the parent and the newly formed phase at the different stages of the transformation can be monitored. These data can be used to elucidate transformation mechanisms (e.g.coherentversusincoherent growth), growth rates and orientation-dependent growth of individual grains. The methodology is demonstrated on the α–γ phase transitions in hydrous Mg2SiO4·H2O up to 22 GPa and 940 K. This transformation most likely occurs in the most abundant mineral of the Earth's upper mantle (Mg0.8Fe0.2SiO4) in deep cold subducted slabs and plays an important role in their subduction behaviour.

scholarly journals Nonlinear Flow Behavior in Packed Beds of Natural and Variably Graded Granular Materials

2019 ◽  
Vol 131 (3) ◽  
pp. 957-983 ◽  
Author(s):  
J. H. van Lopik ◽  
L. Zazai ◽  
N. Hartog ◽  
R. J. Schotting
Keyword(s):  
Grain Size ◽  
Granular Materials ◽  
Flow Behavior ◽  
Nonlinear Flow ◽  
Packed Beds ◽  
Size Distributions ◽  
Flow Conditions ◽  
Grain Size Distributions ◽  
Sand And Gravel ◽  
Nonlinear Flow Behavior

AbstractUnder certain flow conditions, fluid flow through porous media starts to deviate from the linear relationship between flow rate and hydraulic gradient. At such flow conditions, Darcy’s law for laminar flow can no longer be assumed and nonlinear relationships are required to predict flow in the Forchheimer regime. To date, most of the nonlinear flow behavior data is obtained from flow experiments on packed beds of uniformly graded granular materials (Cu = d60/d10 < 2) with various average grain sizes, ranging from sands to cobbles. However, natural deposits of sand and gravel in the subsurface could have a wide variety of grain size distributions. Therefore, in the present study we investigated the impact of variable grain size distributions on the extent of nonlinear flow behavior through 18 different packed beds of natural sand and gravel deposits, as well as composite filter sand and gravel mixtures within the investigated range of uniformity (2.0 < Cu < 17.35) and porosity values (0.23 < n < 0.36). Increased flow resistance is observed for the sand and gravel with high Cu values and low porosity values. The present study shows that for granular material with wider grain size distributions (Cu > 2), the d10 instead of the average grain size (d50) as characteristic pore length should be used. Ergun constants A and B with values of 63.1 and 1.72, respectively, resulted in a reasonable prediction of the Forchheimer coefficients for the investigated granular materials.

A Method for Thinning FIB Prepared TEM Specimens after Lift-Out

2001 ◽  
Vol 7 (S2) ◽  
pp. 940-941 ◽  
Author(s):  
B. B. Rossie ◽  
T. L. Shofner ◽  
S. R. Brown ◽  
S. D. Anderson ◽  
M. M. Jamison ◽  
...  
Keyword(s):  
Bulk Material ◽  
Bulk Sample ◽  
Specimen Preparation ◽  
Wide Spread ◽  
Bulk Specimen ◽  
Site Specific ◽  
Dual Beam ◽  
Main Disadvantage ◽  
A Site ◽  
Membrane Thinning

Advantages of the FIB lift-out technique over traditional H-bar TEM specimen preparation have been recognized. The ability to rapidly (< 1 hour) prepare a site specific TEM specimen without destroying the entire bulk specimen has led to a wide spread reliance on this method. The main disadvantage of this technique is an inability to accomplish additional membrane thinning if required. Traditional H-bar preparation allows additional thinning. However, mechanical polishing is time consuming and the bulk sample is destroyed. A method has been developed which combines the efficient, site specific advantages of the lift-out method with the H-bar's ability to accomplish additional thinning. in this procedure a lift-out specimen is removed from the bulk sample and mounted onto a half-grid in a configuration similar to that employed by the H-bar technique.A 1.0-micron thick lift-out specimen was prepared using a FEI Strata DB-235 FIB dual-beam workstation by sputtering away bulk material leaving a thin membrane containing a desired feature (FIG 1).

scholarly journals Changing depositional environments in the Colombian Fúquene Basin at submillennial time-scales during 284-27 ka from unmixed grain-size distributions and aquatic pollen

2012 ◽  
Vol 91 (1-2) ◽  
pp. 199-214 ◽  
Author(s):  
M. Vriend ◽  
M.H.M. Groot ◽  
H. Hooghiemstra ◽  
R.G. Bogotá-Angel ◽  
J.C. Berrio
Keyword(s):  
Grain Size ◽  
Lacustrine Sediments ◽  
Depositional Environments ◽  
Organic Carbon Content ◽  
Size Distributions ◽  
Glacial Cycles ◽  
Available Energy ◽  
Grain Size Distributions ◽  
Drilling Site ◽  
Mis 5E

AbstractIn a ~60 m long record reflecting the period from 284 ka to 27 ka we analysed grain size distributions (GSD), organic carbon content, and aquatic pollen assemblages at 1-cm increments. The 4768-points time series show with ~60 yr resolution the dynamic history of Lake Fúquene (2540 m alt., 4° N lat.) of the northern Andes during two full interglacial-glacial cycles. GSD show proportions of clay, fine silt, coarse silt, and sand evidencing the location of the sediment source (proximal vs distal) in relation to the drilling site, and available energy to transport sediments in the catchment area. Loss-on-ignition (LOI) values reflect estimates of the abundance of organic matter (OM) in the sediments. Aquatic pollen were grouped into assemblages characteristic of deep water, shallow water, swamp, and wet lake shore environments, reflecting a hydrological gradient sensitive for lake level changes.The End-Member Modelling Algorithm (EMMA) showed that 4 end-members (EMs) explain an optimal proportion (70%) of the observed variation. EMMA is able to unmix GSD of lacustrine sediments in a genetically meaningful way allowing EMs to be interpreted in past depositional and environmental settings. Most unexplained variability is located in the fraction of coarse sediment. OM content was estimated on the basis of LOI data and formed a fifth EM that mainly indicates presence of peat. Changes concur with submillennial-scale variability established in other proxies from this record (Groot et al., 2011). Periods with distinct sediment compositions are 284-243 ka (mainly MIS 8), 243-201 ka (mainly MIS 7), 201-179 ka (mainly MIS 7/6 transition), 179-133 ka (mainly MIS 6), 133-111 ka, (mainly MIS 5e) 111-87 ka (mainly MIS 5d-5b), 87-79 ka (mainly MIS 5a), 79-62 ka (mainly MIS 4), and 62-27 ka (MIS 3) showing sedimentological regimes are climate driven.

Sedimentological signatures of the sub-Amery Ice Shelf circulation

2007 ◽  
Vol 19 (4) ◽  
pp. 497-506 ◽  
Author(s):  
M.A. Hemer ◽  
A.L. Post ◽  
P.E. O'Brien ◽  
M. Craven ◽  
E.M. Truswell ◽  
...  
Keyword(s):  
Dominant Role ◽  
Sediment Cores ◽  
Ice Shelf ◽  
Transport Pathways ◽  
Sediment Distribution ◽  
Bed Elevation ◽  
Amery Ice Shelf ◽  
Basal Melting ◽  
Sand And Gravel ◽  
A Site

AbstractTwo sediment cores collected from beneath the Amery Ice Shelf, East Antarctica describe the physical sedimentation patterns beneath an existing major embayed ice shelf. Core AM01b was collected from a site of basal freezing, contrasting with core AM02, collected from a site of basal melting. Both cores comprise Holocene siliceous muddy ooze (SMO), however, AM01b also recovered interbedded siliciclastic mud, sand and gravel with inclined bedding in its lower 27 cm. This interval indicates an episode of variable but strong current activity before SMO sedimentation became dominant. 14C ages corrected for old surface ages are consistent with previous dating of marine sediments in Prydz Bay. However, the basal age of AM01b of 28250 ± 230 14C yr bp probably results from greater contamination by recycled organic matter. Lithology, 14C surface ages, absolute diatom abundance, and the diatom assemblage are used as indicators of sediment transport pathways beneath the ice shelf. The transport pathways suggested from these indicators do not correspond to previous models of the basal melt/freeze pattern. This indicates that the overturning baroclinic circulation beneath the Amery Ice Shelf (near-bed inflow–surface outflow) is a more important influence on basal melt/freeze and sediment distributions than the barotropic circulation that produces inflow in the east and outflow in the west of the ice front. Localized topographic (ice draft and bed elevation) variations are likely to play a dominant role in the resulting sub-ice shelf melt and sediment distribution.

Sources of sand and gravel on the Northern European Continental Shelf

1998 ◽  
Vol 13 (1) ◽  
pp. 3-13 ◽  
Author(s):  
D. J. Harrison ◽  
C. Laban ◽  
J. O. Leth ◽  
B. Larsen
Keyword(s):  
Large Scale ◽  
Depositional Environments ◽  
Northern Europe ◽  
Glacial Origin ◽  
The North ◽  
Marine Sand ◽  
The 1960S ◽  
The Baltic ◽  
The Uk ◽  
Sand And Gravel

AbstractThe extraction of marine sand and gravel has taken place in a number of countries around the North Sea, the Baltic Sea and English Channel for several centuries, but large-scale dredging for aggregates only began in earnest in the 1960s. Today, marine sands and gravels have an increasing role to play in maintaining European supplies of concreting aggregates as well as material for beach nourishment and constructional fill. The distribution of sand and gravel resources offshore is uneven. They vary in their thickness, their composition and grading, and their proximity to the shore. Many deposits lie in places that are currently inaccessible to the dredging industry.This paper outlines the production of marine sand and gravel in northern Europe and describes the distribution, composition and Quaternary origins of the most important marine sand and gravel resources in northern Europe. Examples are given for the UK, the Netherlands and Denmark, and in summary form for France, Belgium, Norway, Sweden, Ireland and Germany. Most marine sand and gravel deposits are of fluvial or glacial origin and have been reworked to varying degrees by marine and coastal hydrodynamic processes. They represent a range of former depositional environments, including fluvial channel-fill or terrace deposits, glacial meltwater plain deposits, seabed lag gravels and degraded shingle beach or spit deposits, as well as modern marine tidal sandbanks and sandwave deposits.

Ground penetrating radar of northern lacustrine deltas

1991 ◽  
Vol 28 (12) ◽  
pp. 1939-1947 ◽  
Author(s):  
Harry M. Jol ◽  
Derald G. Smith
Keyword(s):  
High Resolution ◽  
Ground Penetrating Radar ◽  
Field Research ◽  
Sedimentary Facies ◽  
Depositional Environments ◽  
Sedimentary Environments ◽  
Peat Deposits ◽  
Big Picture ◽  
Sand And Gravel ◽  
Ground Penetrating

Ground penetrating radar (GPR) was used in several selected deltaic sedimentary environments to better understand subsurface stratigraphy and reconstruct former depositional environments. The profiles provide high-resolution, continuous subsurface data on facies thickness and depths, orientation of major sedimentary structures, postdepositional failure planes, and depth of peat deposits.Field experiments were carried out on six river deltas. Records from four of the deltas exhibit sedimentary facies; a record from one delta shows a possible slump; and records from another delta reveal the thickness and stratigraphic relationships of peat deposits. The delta types are (i) sandy, wave influenced; (ii) sandy, immature wave influenced (steeper middle and lower shoreface); (iii) sandy braided; and (iv) gravelly, fan–foreset.In areas of limited subsurface control (stratigraphic logs from drill core, cutbank exposure, or geophysical logs), radar profiles can provide ''big picture'' perspectives of the subsurface, a view only available in laterally extensive exposures. High-resolution profiles of subsurface stratigraphy and sedimentary facies from GPR provide an opportunity for geomorphologists and sedimentologists to further advance field research. Although GPR has limited success in silt and clay, results from sand and gravel deposits often reveal detailed facies assemblages.

scholarly journals Beaches in McMurdo Sound, Antarctica

2021 ◽  
Author(s):  
◽  
Edward R T Butler
Keyword(s):  
Ross Sea ◽  
Wave Climate ◽  
Ice Shelf ◽  
Mcmurdo Sound ◽  
Ross Ice Shelf ◽  
Local Wave ◽  
Western Side ◽  
Sand And Gravel ◽  
A Site ◽  
Raised Beaches

<p>Modern beaches in McMurdo Sound can be divided into 3 process regimes. Beaches on Ross Island (eastern McMurdo Sound) are characterised by marine processes with little ice modification. On ice-bound western McMurdo Sound, coastal orientation is of paramount importance. Ice thrust features are prominent on south facing beaches, which are open to the predominant wind direction and receive relatively small waves from the fetch restricted south. A greater degree of marine dominance is exhibited by beaches on north facing coasts where sea ice is blown offshore and the beaches are open to the larger storm waves from the eastern Ross Sea. The single most useful indicator of the relative importance of marine and ice processes on the beaches is the roundness of the beach material. Unlike the modern beaches, raised beach ridges at all sites comprise poorly sorted cobbles in a mixed sand and gravel matrix. These are inferred to be storm ridges. In contrast with the raised beaches, the modern beaches on the western side of the Sound have evidence of ice processes on them. This suggests that the modem beach has not experienced the same magnitude storms that produced the raised beaches. The size and frequency of the ridges is a product of the local wave climate. The number of raised beaches at any site is a useful indicator of the paleo-wave climate. More ridges occur in sheltered south facing locations, because they are more protected from open marine conditions, than on beaches in ice-free or north facing locations. When determining the marine limit of a site the most useful features are, low energy marine bedding features (such as flaser bedding) and boulder pavements. Based on inferred process information at the time of deposition, revised estimates of marine limits in McMurdo Sound and a new marine limit at Cape Barne are presented. Because the nature of the raised beaches has not been fully considered by previous authors sea level curves are inaccurate. The reconstruction of the retreat of the Ross Ice Shelf from marine limits in McMurdo Sound shows a three stage stepwise southward retreat of the Ross Ice Shelf. A breakout from somewhere north of Cape Roberts and south of Cape Ross back to Marble Point (on the western side of the Sound) while remaining north of Cape Bird (on the eastern side of the Sound), occurred sometime around 8,000 years ago. Another breakout cleared ice from Cape Bird to somewhere south of Cape Barne and south of Cape Bernacchi around 5,000 years ago. This differs with other authors work (Hall and Denton, 1999, Kellogg et al., 1996, Stuiver et al., 1981) by suggesting a considerably older date for the Ross Ice Sheet retreating from McMurdo Sound. The data presented here suggests that much of McMurdo Sound was ice free about 1,500 years before earlier estimates at about 6,500 years. The effect of the change in deglaciation timing is to reduce isostatic rebound rates. This suggests that there was less ice in McMurdo Sound during the Last Glacial Maximum.</p>

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