scholarly journals Heat Transport and Water Permeability during Cracking of the Landfill Compacted Clay Cover

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Haijun Lu ◽  
Jianjun Liu ◽  
Yuan Li ◽  
Yiqie Dong
Keyword(s):  
Hydraulic Conductivity ◽  
Intensity Factor ◽  
Moisture Content ◽  
Heat Transport ◽  
Moisture Transport ◽  
Crack Depth ◽  
Moisture Loss ◽  
Compacted Clay ◽  
Soil Columns ◽  
Clay Cover

The heat-moisture transport through the compacted clay was observed in laboratory. The hydraulic conductivity of cracked clay under wetting-drying cycles was also investigated. At the early phase of heating, the temperature of soil columns rose fast and moisture decreased dramatically; after this phase, the temperature rose at a lower speed and moisture loss stabilized gradually. The moisture content of compacted clay at 25 cm depth decayed to 0. The crack intensity factor (CIF) of compacted clay was 0.043 and 0.097; the crack depth was about 6.5 cm and 8.2 cm at 50°C and 60°C, respectively. The hydraulic conductivity of compacted clay was within 8.3 × 10−7to 1.5 × 10−5 cm/s after four wetting-drying cycles. This value was 2~3 orders of magnitude higher than that of uncracked clay.

Mathematical Modelling, Moisture Transport, Shrinkage and Nutrient Content Properties in Drying Selected African Leafy Vegetables

2020 ◽  
Vol 36 (1) ◽  
pp. 95-104
Author(s):  
Gibson P Mutuli ◽  
Duncan O Mbuge ◽  
Ayub N Gitau
Keyword(s):  
Activation Energy ◽  
Moisture Content ◽  
Air Temperature ◽  
Moisture Transport ◽  
Leafy Vegetables ◽  
Moisture Loss ◽  
List Type ◽  
Drying Pattern ◽  
Page Model ◽  
And Storage

HighlightsPage model best described their drying pattern at moisture content above 0.5 w.b.Shrinkage linearly correlates to moisture loss.Activation energy correlates to air temperature.Vitamins A, C, and E are preserved by drying and storage. ABSTRACT. The study investigated physical, thermodynamic, and nutritional properties with drying and storage of selected African green leafy vegetables. The vegetables studied were: (Jute Mallow), (Slender Leaf), (Cowpea), (Nightshade), and (Amaranthus). Drying experiment was done at 30°C, 40°C, and 50°C in a convective laboratory dryer and drying was pattern fitted to existing models, moisture diffusivity, and activation energy trends were determined, shrinkage was determined from change in leaf thickness, and vitamins A, C, and E were analyzed using spectroscopy and high-pressure liquid chromatography as freshly harvested and after drying at 40°C and storage for 60 days. Results showed that drying occurred in the falling rate period and Page model could simulate the drying pattern of the vegetables with a ˜97% correlation between the empirical and predicted values with the model prediction being precise above 0.5 moisture content on wet basis (w.b.). Shrinkage was found to be a function of moisture loss at a range of 89% to 98% linear correlation. The rate of moisture loss and activation energy correlated with air temperature. The trend in the drying characteristics and moisture transport of the vegetables was unique with each vegetable. Drying at 40°C and storage for 60 days realized a retention in the scale range of 50% to 75% for vitamins A, C, and E. The study showed that drying is an effective way to preserve the vegetables. Keywords: Mathematical modeling, Mass transfer, Nutrient preservation, Shrinkage, Thermodynamic properties.

Influence of Fly Ash on Clay Liner

2012 ◽  
Vol 518-523 ◽  
pp. 2543-2546
Author(s):  
Xue Jing Sun ◽  
Yong Sheng Zhao ◽  
Zhi Wei Sang
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Moisture Content ◽  
Laboratory Tests ◽  
Optimum Moisture Content ◽  
Compacted Clay ◽  
Landfill Sites ◽  
Cracking Performance ◽  
Desiccation Cracking ◽  
Different Content

Compacted clay is commonly used as an essential material for reducing the permeability in landfill sites. However, compacted clay has defect with shrinkage and desiccation cracking during cyclic drying and wetting, which may increase hydraulic conductivity of compacted clay. It’s necessary to modify clay, and make it have anti-cracking performance. The main objective of the study is to determine the content of fly ash on clay. Laboratory tests were done to determine optimum moisture content, hydraulic conductivity, volume shrinkage on different content fly ash modified clay. It was determined that a certain proportion of fly ash can improve the permeability of clay, and reduce the cracking clay.

scholarly journals Hydraulic and Swell–Shrink Characteristics of Clay and Recycled Zeolite Mixtures for Liner Construction in Sustainable Waste Landfill

2021 ◽  
Vol 13 (13) ◽  
pp. 7301
Author(s):  
Marcin K. Widomski ◽  
Anna Musz-Pomorska ◽  
Wojciech Franus
Keyword(s):  
Hydraulic Conductivity ◽  
Exchange Capacity ◽  
Saturated Hydraulic Conductivity ◽  
Clay Soils ◽  
Compacted Clay ◽  
Clay Liner ◽  
Compacted Clay Liner ◽  
Drying And Rewetting ◽  
Swelling Characteristics ◽  
Shrinkage And Swelling

This paper presents research considering hydraulic as well as swelling and shrinkage characteristics of potential recycled fine particle materials for compacted clay liner for sustainable landfills. Five locally available clay soils mixed with 10% (by mass) of NaP1 recycled zeolite were tested. The performed analysis was based on determined plasticity, cation exchange capacity, coefficient of saturated hydraulic conductivity after compaction, several shrinkage and swelling characteristics as well as, finally, saturated hydraulic conductivity after three cycles of drying and rewetting of tested specimens and the reference samples. The obtained results showed that addition of zeolite to clay soils allowed reduction in their saturated hydraulic conductivity to meet the required threshold (≤1 × 10−9 m/s) of sealing capabilities for compacted clay liner. On the other hand, an increase in plasticity, swelling, and in several cases in shrinkage, of the clay–zeolite mixture was observed. Finally, none of the tested mixtures was able to sustain its sealing capabilities after three cycles of drying and rewetting. Thus, the studied clayey soils mixed with sustainable recycled zeolite were assessed as promising materials for compacted liner construction. However, the liner should be operated carefully to avoid extensive dissication and cracking.

scholarly journals Effect of Drying on the Rehydration Properties of Some Selected Shellfish

2020 ◽  
pp. 42-48
Author(s):  
D. B. Kiin-Kabari ◽  
N. Obasi
Keyword(s):  
Moisture Content ◽  
Proximate Composition ◽  
Crude Protein ◽  
Moisture Loss ◽  
Rehydration Ratio ◽  
Crude Fibre ◽  
Oven Drying ◽  
Water Imbibition ◽  
Nutritional Qualities ◽  
Sample Water

This study was conducted to evaluate the effect of oven drying on the proximate composition and rehydration characteristics of shellfish. Shellfish studied included rough and smooth periwinkle, oyster and whelk. Proximate composition of the fresh samples were determined. Then dried in the oven to a moisture content of 10% and further rehydrated with distill water in sample water ratio of 1:40 and allowed to equilibrate. Proximate composition of the fresh shellfish showed that moisture content ranged from 82.38 to 69.24% with fresh smooth periwinkle having the highest moisture value while whelk had the lowest. The results also showed that whelk had the highest values for ash (2.92%), crude protein (18.83%) and crude fibre (3.71%) when compared to other samples. On rehydration, a moisture loss of 11.75%, 13.28%, 19.24% and 22.04% were observed for rough periwinkle, smooth periwinkle, oyster and whelk, respectively. The results for rehydration indices revealed that dehydration ratio was significantly (p<0.05) high for whelk (1.44), followed by oyster (1.29), rough periwinkle (1.23) and lastly, smooth periwinkle 1.20. Rehydration ratio of whelk (1.47) was equally significantly higher, followed by oyster (1.33) and the least were rough and smooth periwinkle (1.17). For coefficient of reconstitution, oyster recorded the highest value of 1.03, followed by whelk 1.02, rough periwinkle 0.95 and smooth periwinkle 0.98. Rate of water imbibition revealed a sharp increase in the water content of smooth periwinkle up to 240 min and thereafter, it slowed down until equilibrium was reached. In terms of rough periwinkle, oyster and whelk; water imbibition took place with rehydration time up to 300 min, 210 min and 270 min, respectively, thereafter they slowed down. The results have demonstrated that the rate in which oven drying affect the physical and nutritional qualities of shellfish differs.

scholarly journals A Study on Factors Influencing the Determination of Moisture Content of Fibrous Peat

2011 ◽  
Vol 2 (2) ◽  
pp. 39-47 ◽  
Author(s):  
Pui Tau Shien ◽  
Seneviratne H.N. ◽  
Dygku Salma Awg Ismail
Keyword(s):  
Moisture Content ◽  
Particle Density ◽  
Peat Soil ◽  
Test Procedure ◽  
Field Measurements ◽  
Standard Test ◽  
Moisture Loss ◽  
Fibrous Peat ◽  
Saturated Sample

Fibrous peat is an undrained peat that usually possesses very high moisture content. However, not all experimental procedures are applicable for determination of moisture content of fibrous peat. This research is aimed at examining the determination of insitu moisture content of fibrous peat using field measurements. The peat soil samples were collected at shallow depths from Asajaya at Kota Samarahan and Taman Kopodims at Matang , Kuching Sarawak by using peat auger. The laboratory tests such as determination of moisture content, fiber content, particle density and ash content were conducted on the collected samples in order to establish relationships between the parameters. Undisturbed peat samples from Matang were subjected to falling head permeability test to determine the saturated permeability. The saturated sample were then allowed to drain freely to simulate the moisture loss possible during sampling when samples were brought out of boreholes. The test results showed that moisture content varies according to the drying temperature and position of the soil sample (top, middle and bottom) during sampling. Comparing samples from both locations, peat soil from Kota Samarahan possessed higher moisture content. The saturated permeability of peat sample was in the range of 2.62 – 3.05 cm/s. The free draining trial showed that moisture loss during sampling significantly influence the moisture content measurement. The variation in value of moisture content for fibrous peat may occurs due to several factors such as existing ground water table, sampling method by boring, existing standard test procedure which is not suitable for peat soils requirement and also because of the physical properties which varied according to depth of soil.

scholarly journals Moisture transport from the Arctic: a characterization from a Lagrangian perspective

2018 ◽  
Vol 44 (2) ◽  
pp. 659 ◽  
Author(s):  
M. Vázquez ◽  
R. Nieto ◽  
A. Drumond ◽  
L. Gimeno
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Moisture Transport ◽  
Hydrological Cycle ◽  
Moisture Loss ◽  
Lagrangian Model ◽  
The Arctic ◽  
Sea Ice Extent ◽  
The Arctic Ocean ◽  
Moisture Supply

The Arctic Ocean has suffered extreme reductions in sea ice in recent decades, and these observed changes suggest implications in terms of moisture transport. The Arctic region is a net sink of moisture in terms of the total hydrological cycle, however, its role as a moisture source for specific regions has not been extensively studied. Our results show that 80% of the moisture supply from the Arctic contributes to precipitation over itself, representing about 8% of the global moisture supply to the Arctic, the remaining 20% is distributed in the surrounding. A reduction in the sea ice extent could make the Arctic Ocean a slightly higher source of moisture to itself or to the surrounding areas. The analysis of the areas affected by Arctic moisture transport is important for establishing those areas vulnerable to change in a framework of a growing sea ice decline. To this end, the Lagrangian model FLEXPART was used in this work to establish the main sinks for the Arctic Ocean, focusing on the moisture transport from this region. The results suggest that most of the moisture loss occurs locally over the Arctic Ocean itself, especially in summer. Some moisture contribution from the Arctic Ocean to continental areas in North America and Eurasia is also noted in autumn and winter especially from Central Arctic, the East Siberian Sea, the Laptev, Kara, Barents, East Greenland and Bering Seas, and the Sea of Okhotsk.

scholarly journals Numerical Modelling of Moisture Loss during Controlled Drying of Marine Archaeological Wood

Forests ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1662
Author(s):  
Gabriel Lipkowitz ◽  
Karoline Sofie Hennum ◽  
Eleonora Piva ◽  
Eleanor Schofield
Keyword(s):  
Moisture Content ◽  
Numerical Modelling ◽  
Visual Observation ◽  
Moisture Loss ◽  
Conservation Strategies ◽  
Residual Water ◽  
Archaeological Wood ◽  
Sample Depth ◽  
Representative Model ◽  
First Time

If left to dry uncontrollably following excavation, marine archaeological wood suffers significant and irreparable damage. Conservation treatments are required to consolidate degraded wood and to remove residual water. Drying must be controlled to eliminate erratic and heterogeneous water removal. Monitoring and understanding the drying process progression is invaluable information to garner real-time knowledge to correlate with chemical and physical material properties, and to develop future conservation strategies. Here, polyethylene glycol (PEG) consolidated marine archaeological wood was periodically sampled during drying to determine the moisture content as a function of location, time, and sample depth. The heterogeneous nature of the material leads to significant noise across spatial and temporal measurements, making it challenging to elucidate meaningful conclusions from visual observation of the raw data. Therefore, the spatiotemporal data was computationally analysed to produce a representative model of the ship’s drying, illustrated by a dynamic simulation. From this we can quantitatively predict the drying rate, determine the depth-dependence of drying, and estimate the resulting equilibrium moisture content. This is the first time such simulations have been carried out on this material and conservation process, demonstrating the power of applying numerical modelling to further our understanding of complex heritage data.

Entrapment, stability, and persistence of air bubbles in soil water

Soil Research ◽  
1969 ◽  
Vol 7 (2) ◽  
pp. 79 ◽  
Author(s):  
AJ Peck
Keyword(s):  
Hydraulic Conductivity ◽  
Moisture Content ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Equilibration Time ◽  
Air Bubbles ◽  
Air Entrapment ◽  
Water Characteristics ◽  
Spherical Bubbles ◽  
Entrapped Air

Air bubbles in soil water affect both hydraulic conductivity and moisture content at a given capillary potential. Consequently changes in the volume of entrapped air, which are not included in the specification of relationships between hydraulic conductivity, moisture content, and capillary potential, will affect all soil-water interactions. Current understanding of the process of air bubble entrapment during infiltration suggests that, in nature, significant air entrapment will often occur. It is shown that infiltrating water can dissolve only a very small volume of air, much less than the amount usually entrapped. Air bubbles in saturated soils are unstable since their pressure must exceed atmospheric, resulting in a diffusive flux of dissolved air from bubbles to menisci contacting the external atmosphere. However, stable bubbles are possible in unsaturated soils. Bubbles which are constrained by pore architecture to non-spherical shapes are usually stable, and spherical bubbles can be stable when the magnitude of the capillary potential exceeds about 3 bars. An approximate analysis of the characteristic time of bubble equilibration indicates that, in an example, it is of order 104 sec, but it may be greater or less by at least a factor 10. Since the equilibration time will be often at least as large as the period of significant soil temperature changes, it cannot be assumed that the entrapped air in a field soil is in an equilibrium state. In such circumstances unstable bubbles may be quasi-permanent. It is suggested that the slow growth of entrapped bubbles may account for the anomalously slow release of water observed in some outflow experiments. Changes of entrapped air volume may also account for the reported dependence of soil-water characteristics on the magnitude of the steps of capillary potential.

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