Matrix suction and diffusive transport in centrifuge models: Reply

1995 ◽  
Vol 32 (1) ◽  
pp. 180-181
Author(s):  
R.J. Mitchell
Keyword(s):  
Diffusive Transport ◽  
Centrifuge Models ◽  
Matrix Suction

Matrix suction and diffusive transport in centrifuge models

1994 ◽  
Vol 31 (3) ◽  
pp. 357-363 ◽  
Author(s):  
R.J. Mitchell
Keyword(s):  
Soil Surface ◽  
Fine Sand ◽  
Lateral Spread ◽  
Diffusive Transport ◽  
Centrifuge Modelling ◽  
Deep Soil ◽  
Contaminant Fate ◽  
Centrifuge Models ◽  
Matrix Suction ◽  
Vadoze Zone

Centrifuge modelling of the lateral spread of a conservative solute in a partly saturated fine sand has been accomplished in a 3 m radius centrifuge at simulated gravitational accelerations of 25 and 50 g. The distributions of the contaminant after 2 months, 6 months, and 1 year of prototype time were found experimentally by dissection of models. The results support the contention that centrifuge modelling does correctly recreate prototype transport phenomena, including transport due to matrix suction, in partly saturated fine sand. For the conditions modelled, it was found that all of the contaminant introduced at the soil surface became immobilized, for at least 1 year, inthe upper 2–3 m of the 6 m deep soil profile. Key words : centrifuge modelling, contaminant fate, vadoze zone, matrix suction, diffusion.

Development of Experimental P-Y Curves from Centrifuge Tests for Piles Subjected to Static Loading and Liquefaction-Induced Lateral Spreading

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Milad Souri
Keyword(s):  
Static Loading ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Pressure Ratio ◽  
Lateral Spreading ◽  
American Petroleum Institute ◽  
Unique Contribution ◽  
Pile Groups ◽  
Centrifuge Tests ◽  
Centrifuge Models

The results of five centrifuge models were used to evaluate the response of pile-supported wharves subjected to inertial and liquefaction-induced lateral spreading loads. The centrifuge models contained pile groups that were embedded in rockfill dikes over layers of loose to dense sand and were shaken by a series of ground motions. The p-y curves were back-calculated for both dynamic and static loading from centrifuge data and were compared against commonly used American Petroleum Institute p-y relationships. It was found that liquefaction in loose sand resulted in a significant reduction in ultimate soil resistance. It was also found that incorporating p-multipliers that are proportional to the pore water pressure ratio in granular materials is adequate for estimating pile demands in pseudo-static analysis. The unique contribution of this study is that the piles in these tests were subjected to combined effects of inertial loads from the superstructure and kinematic loads from liquefaction-induced lateral spreading.

scholarly journals The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Viet Cao ◽  
Ghinwa Alyoussef ◽  
Nadège Gatcha-Bandjun ◽  
Willis Gwenzi ◽  
Chicgoua Noubactep
Keyword(s):  
Contact Time ◽  
Diffusive Transport ◽  
Iron Hydroxides ◽  
Iron Corrosion ◽  
Short Term ◽  
Batch Studies ◽  
Water Decontamination ◽  
Co Precipitation

AbstractMetallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.

scholarly journals Water-Enhanced Flux Changes under Dynamic Temperatures in the Vertical Vapor-Phase Diffusive Transport of Volatile Organic Compounds in Near-Surface Soil Environments

2021 ◽  
Vol 13 (12) ◽  
pp. 6570
Author(s):  
Asma Akter Parlin ◽  
Monami Kondo ◽  
Noriaki Watanabe ◽  
Kengo Nakamura ◽  
Mizuki Yamada ◽  
...  
Keyword(s):  
Air Quality ◽  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Vapor Phase ◽  
Inverse Correlation ◽  
Diffusive Transport ◽  
Near Surface ◽  
Voc Emissions ◽  
Transport Behavior ◽  
Volatile Organic

The quantitative understanding of the transport behavior of volatile organic compounds (VOCs) in near-surface soils is highly important in light of the potential impacts of soil VOC emissions on the air quality and climate. Previous studies have suggested that temperature changes affect the transport behavior; however, the effects are not well understood. Indeed, much larger changes in the VOC flux under in situ dynamic temperatures than those expected from the temperature dependence of the diffusion coefficients of VOCs in the air have been suggested but rarely investigated experimentally. Here, we present the results of a set of experiments on the upward vertical vapor-phase diffusive transport of benzene and trichloroethylene (TCE) in sandy soils with water contents ranging from an air-dried value to 10 wt% during sinusoidal temperature variation between 20 and 30 °C. In all experiments, the flux from the soil surface was correlated with the temperature, as expected. However, the changes in flux under wet conditions were unexpectedly large and increased with increasing water content; they were also larger for TCE, the volatility of which depended more strongly on the temperature. Additionally, the larger flux changes were accompanied by a recently discovered water-induced inverse correlation between temperature and flux into the overlying soil. These results demonstrated that the flux changes of VOCs under dynamic temperatures could be increased by volatilization-dissolution interactions of VOCs with water. Future extensive studies on this newly discovered phenomenon would contribute to a better understanding of the impacts of soil VOC emissions on the air quality and climate.

Diffusive transport in highly corrugated channels

2019 ◽  
Vol 383 (11) ◽  
pp. 1084-1091
Author(s):  
Fabio Cecconi ◽  
Valon Blakaj ◽  
Gabriele Gradoni ◽  
Angelo Vulpiani
Keyword(s):  
Diffusive Transport

AC Electrokinetics for Biosensors

2004 ◽  
Author(s):  
M. Sigurdson ◽  
C. Meinhart ◽  
D. Wang
Keyword(s):  
Electric Fields ◽  
Dna Hybridization ◽  
Fluid Motion ◽  
Diffusive Transport ◽  
Analyte Concentration ◽  
Ac Electrokinetics ◽  
Ac Electric Fields ◽  
Binding Rate ◽  
Electrothermal Flow ◽  
Biosensor Device

We develop here tools for speeding up binding in a biosensor device through augmenting diffusive transport, applicable to immunoassays as well as DNA hybridization, and to a variety of formats, from microfluidic to microarray. AC electric fields generate the fluid motion through the well documented but unexploited phenomenon, Electrothermal Flow, where the circulating flow redirects or stirs the fluid, providing more binding opportunities between suspended and wall-immobilized molecules. Numerical simulations predict a factor of up to 8 increase in binding rate for an immunoassay under reasonable conditions. Preliminary experiments show qualitatively higher binding after 15 minutes. In certain applications, dielectrophoretic capture of passing molecules, when combined with electrothermal flow, can increase local analyte concentration and further enhance binding.

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