scholarly journals An Improved Predictive Model for Determining the Permeability Coefficient of Artificial Clayey Soil Based on Double T2 Cut-Offs

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Zhen Lu ◽  
Aimin Sha ◽  
Junfeng Gao ◽  
Meng Jia ◽  
Wentong Wang
Keyword(s):  
Permeability Coefficient ◽  
Clayey Soil ◽  
Relaxation Times ◽  
Absolute Error ◽  
Engineering Properties ◽  
Evaporation Process ◽  
Transverse Relaxation ◽  
Saturated Sample ◽  
Improved Model ◽  
Tc Model

Permeability is one of the most important engineering properties of clayey soil. However, the traditional method for determining the permeability coefficient is time-consuming. To establish a simple and accurate predictive method to obtain the permeability coefficient of artificial clayey soil based on the double cut-off transverse relaxation times (T2 cut-offs) using low-field nuclear magnetic resonance (NMR) technology, eight kinds of artificial clayey soil with different mineralogical compositions were prepared in the laboratory. Evaporation tests at 40°C were carried out on the saturated artificial clayey soil samples in an oven. During the evaporation process, NMR tests were also performed on the artificial clayey soil every hour. The results showed that the evaporation process could be divided into three stages according to different evaporation rates: the constant rate stage (CRS), the falling rate stage (FRS), and the residual stage (RS). The water evaporated in the CRS and FRS was defined as the absolute movable water and the partially movable water, respectively. The water that could not evaporate in the RS was defined as the immovable water. Based on the cumulative signal amplitudes in the T2 spectrum corresponding to different kinds of water, the double T2 cut-offs were defined. On the basis of the double T2 cut-offs and T2 spectrum of the saturated sample, an improved Timur–Coates (TC) model was established. The prediction capability of the improved model was evaluated by finding the determination coefficient (R2), mean absolute error (MAE), and root-mean-square error (RMSE). Compared with the typical TC model, the prediction accuracy of the improved model was much higher. In addition, the relationships between the double T2 cut-offs and fractal dimension (D) of the T2 spectrum of saturated artificial clayey soil were also identified.

Improvement in the Engineering Properties of Clayey Soil Using Sodium Chloride

2020 ◽  
Author(s):  
Harpinder Pal Singh ◽  
Jaspreet Singh Chana ◽  
Gurpreet Singh ◽  
Hardev Singh ◽  
Manvir Singh
Keyword(s):  
Sodium Chloride ◽  
Clayey Soil ◽  
Engineering Properties

Proton magnetic relaxation of water sorbed by methaemoglobin crystals

1973 ◽  
Vol 331 (1587) ◽  
pp. 457-468 ◽  
Keyword(s):  
Relaxation Rate ◽  
Relaxation Times ◽  
Transverse Relaxation Rate ◽  
Ferric Ions ◽  
Transverse Relaxation ◽  
Water Binding ◽  
Adsorption Sites ◽  
Protein Molecules ◽  
Proton Magnetic Relaxation ◽  
Limiting Value

P. m. r. relaxation times ( T 1 and T 2 ) have been measured as a function of regain and temperature for water sorbed by lyophilized methaemoglobin. The purpose of the work was to gain information regarding the nature and extent of water binding by the protein molecules. The T 1 results are interpreted in terms of an exchange between the sixth ligand position of the Fe (III) and other adsorption sites on the protein. At high temperatures the relaxation rate at a given regain reaches a limiting value which allows the fraction of ferric ions hydrated to be calculated. Above 16% regain all the Fe (III) is hydrated. At 21 and 35% regains a maximum appears in the relaxation rate at about -46 °C indicating a contribution from a more mobile phase which produces a T 1 minimum at that temperature. The T 2 data are consistent with a model in which the main contribution to the transverse relaxation rate comes from a tightly bound fraction of the water with ω 0 Ƭ c ≫1. The temperature dependence of T 2 exhibits three different regions: ( a ) a low temperature region where lg T 2 ∝ T -1 ; ( b ) an intermediate region with a steeper increase of T 2 with temperature; and ( c ) a high temperature where T 2 levels off.

scholarly journals The Improvement of Engineering Properties of Expansive Soil using Waste Glass Powder (WGP) and Quick Lime

2021 ◽  
Vol 9 (VI) ◽  
pp. 3598-3604
Author(s):  
Bhagwan Singh Lodha
Keyword(s):  
Glass Powder ◽  
Clayey Soil ◽  
Expansive Soil ◽  
Waste Glass ◽  
Engineering Properties ◽  
Binding Property ◽  
Unconfined Compression Test ◽  
Quick Lime ◽  
Waste Glass Powder ◽  
Consolidation Settlement

This study was carried out with an intention to observe any sign of improvement of expansive clayey soil due to the addition of Waste Glass Powder (WGP) with it. In this laboratory work clayey (BC) type soil has been chosen. The reason behind choosing clay is that it has many problems. The main problem is that it undergoes consolidation settlement due to the application of long-term loading. Another problem is it shrinks significantly if it is dried and expands significantly, if it absorbs moisture than exerts much pressure on the substructure. Quick Lime and Waste Glass powder is chosen to check the improvement because waste glass powder is cohesionless material and also contains silica, lime etc. Addition of cohesionless material to the cohesive soil means it will lesser the consolidation settlement and expansive nature of soil and Lime provides binding property. To investigate the traditional methods of analysing, the effect of additives on soil has been adopted i.e., conducting several tests of untreated soil and soil treated with waste glass and lime with varying percentage and then comparing the results obtained. The tests that were carried out in this study are Compaction test (Proctor test), Consolidation test (unconfined compression test). MDD and Unconfined compressive strength increases with the addition of glass powder and lime with oven dried expansive soil.

scholarly journals Combination of MRI and SEM to Assess Changes in the Chemical Properties and Permeability of Porous Media due to Barite Precipitation

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 226 ◽  
Author(s):  
Jenna Poonoosamy ◽  
Sabina Haber-Pohlmeier ◽  
Hang Deng ◽  
Guido Deissmann ◽  
Martina Klinkenberg ◽  
...  
Keyword(s):  
Porous Media ◽  
Magnetic Resonance ◽  
Reactive Transport ◽  
Relaxation Times ◽  
Chemical Properties ◽  
Column Experiment ◽  
Transverse Relaxation Time ◽  
Gas Production ◽  
Transport Modelling ◽  
Transverse Relaxation

The understanding of the dissolution and precipitation of minerals and its impact on the transport of fluids in porous media is essential for various subsurface applications, including shale gas production using hydraulic fracturing (“fracking”), CO2 sequestration, or geothermal energy extraction. In this work, we conducted a flow through column experiment to investigate the effect of barite precipitation following the dissolution of celestine and consequential permeability changes. These processes were assessed by a combination of 3D non-invasive magnetic resonance imaging, scanning electron microscopy, and conventional permeability measurements. The formation of barite overgrowths on the surface of celestine manifested in a reduced transverse relaxation time due to its higher magnetic susceptibility compared to the original celestine. Two empirical nuclear magnetic resonance (NMR) porosity–permeability relations could successfully predict the observed changes in permeability by the change in the transverse relaxation times and porosity. Based on the observation that the advancement of the reaction front follows the square root of time, and micro-continuum reactive transport modelling of the solid/fluid interface, it can be inferred that the mineral overgrowth is porous and allows the diffusion of solutes, thus affecting the mineral reactivity in the system. Our current investigation indicates that the porosity of the newly formed precipitate and consequently its diffusion properties depend on the supersaturation in solution that prevails during precipitation.

Cross-linked polydimethylsiloxane colloid as novel contrast agent for gastrointestinal magnetic resonance imaging: Transient nuclear Overhauser effect within the interface

2020 ◽  
Vol 35 (2) ◽  
pp. 264-273
Author(s):  
Fu-Hu Su ◽  
Wang-Chuan Xiao ◽  
Sheann-Huei Lin ◽  
Qiyong Li
Keyword(s):  
Magnetic Resonance ◽  
Nuclear Overhauser Effect ◽  
Relaxation Times ◽  
Resonance Imaging ◽  
Transverse Relaxation ◽  
Overhauser Effect ◽  
Nuclear Magnetic Resonance Spectra ◽  
Relaxation Experiments ◽  
Longitudinal Relaxation ◽  
Nuclear Overhauser

With good contrast in T1 and T2 weighted imaging as well as low toxicity in 3- (4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, this work proposes the cross-linked polydimethylsiloxane colloids as a novel non-ionic contrast agent for gastrointestinal magnetic resonance imaging. The experiments of nuclear magnetic resonance spectra and relaxation show that within the interface of the colloids, there are nuclear Overhauser effect and transient nuclear Overhauser effect (cross-relaxation). Regarding the longitudinal relaxation experiments of CH2CH2O segments of Tween 80, a two spins system is found and modeled well by the equation [Formula: see text] which is deduced based on the transient nuclear Overhauser effect proposed by Solomon. The arbitrary constant X is additionally added with the initial conditions ( Iz −  I0) t=0 = −2 XS0 and ( Sz −  S0) t=0 = −2 S0. For the two spins system, D1 and T1 are corresponding to longitudinal relaxation times of the bound water and the CH2CH2O respectively. Concerning the transverse relaxation experiments of the CH2CH2O, they agree with the equation with three exponential decays, defined by three relaxation times, likely corresponding to three mechanisms. These mechanisms possibly are intramolecular and intermolecular dipole–dipole (DD) interactions and scalar coupling. Within the interface, hydrogen bonding causes the positive nuclear Overhauser effect of the CH2CH2O’s nuclear magnetic resonance spectra, the transient nuclear Overhauser effect of the CH2CH2O’s longitudinal relaxation experiments and the intermolecular dipole–dipole interactions of the CH2CH2O’s transverse relaxation experiments.

scholarly journals Effect of gypsum content on unsaturated engineering properties of clayey soil

2020 ◽  
Vol 9 (1) ◽  
pp. 84
Author(s):  
Mohammed N J Alzaidy
Keyword(s):  
Shear Strength ◽  
Clayey Soil ◽  
Engineering Properties ◽  
Water Retention Curve ◽  
Shear Strength Parameters ◽  
Swelling Potential ◽  
Soil Water Retention Curve ◽  
Strength Parameters ◽  
Gypsum Content ◽  
Vapour Diffusion

Many of gypsum soils have existed in arid and semi-arid lands. It is considered one of the most problematic soils because of its complicated and unpredicted behavior when exposure to moisture. Extensive researches have been conducted in Iraq to observe the behavior of such soil and to suggest safety restrictions for the collapse and set practical precautions for the structures. This study investigated the effect of gypsum content on some unsaturated engineering properties of a clayey soil. Three different proportions of gypsum (0%, 5% and 20% by weight of the parent soil) were added and tested. The samples have been subjected to swelling potential test, soil water retention curve (SWRC), vapour diffusion and shear strength parameters. It is observed that gypsum content has a significant influence on SWRC, whereas, soil that has high gypsum content made SWRC with higher variables represented by air entry values and residual state. On the other hand, an increase in gypsum content led to a reduction of swelling potential and shear strength parameters. The results of vapour diffusion indicate that gypsum content could modify the microstructure in an unsaturated state and reduce the vapour diffusion through the soil.  

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