Laboratory test study on the effect of freeze–thaw cycles on strength and hydraulic conductivity of high water content stabilized dredged sediments

2016 ◽  
Vol 53 (6) ◽  
pp. 1038-1045 ◽  
Author(s):  
Gregory Makusa ◽  
Josef Mácsik ◽  
Göran Holm ◽  
Sven Knutsson
Keyword(s):  
Hydraulic Conductivity ◽  
High Water ◽  
High Water Content ◽  
Initial Water ◽  
Dredged Sediments ◽  
Freeze Thaw ◽  
Test Study ◽  
Thaw Consolidation ◽  
Permanent Loss ◽  
The Impact

Dredged sediments with initial water contents between 200% and 400% were treated with single and composite binders. Samples were subjected to open and semi-closed freeze–thaw (f–t) cycles to investigate the impact of f–t cycling on hydraulic conductivity (HC) and unconfined compressive strength (UCS). A grace period (GP) for thaw consolidation is included to assess healing potential of the affected stabilized mass. Findings of this study show that the impact of f–t cycles depends on initially achieved UCS and HC values prior to the f–t cycling and time of testing after f–t cycles. The HC of specimens with an initial UCS value of 87 kPa increased with number of f–t cycles. The UCS values decreased in the range of 50%–80% when specimens were tested directly after the thaw period and values decreased in the range of 14%–60% when specimens were tested at the end of the GP. The HC of specimens with an initial UCS value of 299 kPa remained almost the same. These samples experienced permanent loss in the UCS values, irrespective of time of testing. Detrimental effects of the freezing action on the UCS were greater under semi-closed than open freezing conditions.

scholarly journals Irrigation Control and Physiological Responses of Nursery-grown Black Spruce Seedlings (1+0) Cultivated in Air-slit Containers

HortScience ◽  
2004 ◽  
Vol 39 (3) ◽  
pp. 599-605 ◽  
Author(s):  
Onil Bergeron ◽  
Mohammed S. Lamhamedi ◽  
Hank A. Margolis ◽  
Pierre Y. Bernier ◽  
Debra C. Stowe
Keyword(s):  
Hydraulic Conductivity ◽  
Water Content ◽  
Black Spruce ◽  
Growing Season ◽  
High Water ◽  
Water Relation ◽  
Time Domain Reflectometry ◽  
High Water Content ◽  
Root Hydraulic Conductivity ◽  
Irrigation Regimes

Air-slit containerized (IPL 25-350A) black spruce [Picea mariana (Mill) BSP; 1+0] seedlings, were subjected to four irrigation regimes (IR-15%, IR-30%, IR-45%, and IR-60%, by volume, cm3 water/cm3 substrate) under tunnel conditions in a forest nursery. Irrigation regimes were controlled by time-domain reflectometry during the first growing season. With exception of midday water potential, water relation and gas exchange variables were unaffected by substrate water content. There were no significant differences in height, diameter or number of needle primordia of the seedlings grown under IR-15%, IR-30%, and IR-45%. Seedlings grown in a substrate with a high water content (IR-60%) had lower oven-dry biomass and higher cuticular transpiration rates than seedlings grown under the three other irrigation regimes. Root hydraulic conductivity was not affected by irrigation regime, but showed a general decrease towards the end of the growing season. Variation in root hydraulic conductivity was most likely related to root growth and degree of lignification. Seedlings that had been exposed to IR-60% during the first growing season remained smaller than the other seedlings throughout the second growing season. Results of this study indicate that nursery managers can reduce the quantity of irrigation water used without significantly affecting the growth or physiology of air-slit containerized black spruce seedlings (1+0) grown under tunnel conditions.

scholarly journals The impacts of freeze–thaw cycles on saturated hydraulic conductivity and microstructure of saline–alkali soils

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wenshuo Xu ◽  
Kesheng Li ◽  
Longxiao Chen ◽  
Weihang Kong ◽  
Chuanxiao Liu
Keyword(s):  
Hydraulic Conductivity ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Water Content ◽  
Size Distribution ◽  
Saturated Hydraulic Conductivity ◽  
High Water Content ◽  
Soil Permeability ◽  
Freeze Thaw ◽  
Alkali Soil

AbstractStudy on the microscopic structure of saline–alkali soil can reveal the change of its permeability more deeply. In this paper, the relationship between permeability and microstructure of saline–alkali soil with different dry densities and water content in the floodplain of southwestern Shandong Province was studied through freeze–thaw cycles. A comprehensive analysis of soil samples was conducted using particle-size distribution, X-ray diffraction, freeze–thaw cycles test, saturated hydraulic conductivity test and mercury intrusion porosimetry. The poor microstructure of soil is the main factor that leads to the category of micro-permeable soil. The porosity of the local soil was only 6.19–11.51%, and ultra-micropores (< 0.05 μm) and micropores (0.05–2 μm) dominated the pore size distribution. Soil saturated water conductivity was closely related to its microscopic pore size distribution. As the F–T cycles progressed, soil permeability became stronger, with the reason the pore size distribution curve began to shift to the small pores (2–10 μm) and mesopores (10–20 μm), and this effect was the most severe when the freeze–thaw cycle was 15 times. High water content could promote the effects of freeze–thaw cycles on soil permeability and pore size distribution, while the increase of dry density could inhibit these effects. The results of this study provide a theoretical basis for the remediation of saline–alkali soil in the flooded area of Southwest Shandong.

scholarly journals Initial Moisture Content of Corncobs Plays an Important Role in Maintaining its Quality during Storage

2018 ◽  
Vol 38 (2) ◽  
pp. 167
Author(s):  
Lince Mukkun ◽  
Herianus J.D. Lalel ◽  
Yuliana Tandirubak
Keyword(s):  
Moisture Content ◽  
Water Content ◽  
Insect Pests ◽  
Initial Moisture Content ◽  
High Water ◽  
High Water Content ◽  
Initial Water Content ◽  
Initial Water ◽  
Plant Materials ◽  
Randomized Design

Maize is one of the important staple foods for people in Timor, East Nusa Tenggara Province, Indonesia. Subsistent farmers store the maize for their own consumption until the next harvest season, for seed and feed.  However, high initial water content of the kernel due to improper drying prior storage initiate serious damage and losses during the maize storage.  High water content promotes the growth of fungi and insects, and increase respiration rate, resulting in rapid deterioration of maize. The purpose of this study was to determine the initial moisture content that might minimize damage and losses of maize in the farmers’ storage, and to study the effects of some plant materials that are used to smoke corns before storage. The experiment was initiated by sun-drying the harvested corncobs for 0, 2, 4, 6, 8, and 10 days (6 hours a day). This experiment was designed using Completely Randomized Design with 6 treatments and 3 replications. Dried corncobs were stored in the farmer’s storage for 4 months. The effects of maize kernels’ initial water content on the development of water content in kernels; the percentage of damaged kernels; and the species of pathogen and insects were investigated during storage with 2-week intervals.  The results demonstrated that drying the corncobs prior storage for 10 days, resulting in 12.96% of water content, significantly decreased the percentage of seed damage to 6.5%, as compared to without drying process which resulted  in 63%.  Aspergillus flavus, Fusarium sp., and Penicillium sp were found to be the main pathogen during storage.  There are no insect pests found during the storage. 

Coupled Fluid-Mechanical Analysis of Deep Tunnel in Water-Soaked Karst Stratum

2012 ◽  
Vol 170-173 ◽  
pp. 1744-1748
Author(s):  
Xun Li ◽  
Chuan He ◽  
Guo Wen Xu
Keyword(s):  
Permeability Coefficient ◽  
Water Pressure ◽  
Drainage System ◽  
High Water ◽  
Mechanical Analysis ◽  
Surrounding Rock ◽  
Shield Tunnel ◽  
Deep Tunnel ◽  
Initial Water ◽  
The Impact

To reduce the impact on water resource and the environment, the ‘controlled drainage principle’ is complied with when designing waterproof and drainage system of tunnel in recent years. For deep tunnel in Water-soaked Karst Stratum, the lining would sustain high water pressure that was caused by the unreasonable design of waterproof and drainage system. Taking a railway shield tunnel as an engineering background, the water shut-off effect of grouting circle, minimum controlled discharge of tunnel and the water pressure of lining properties were studied. The results indicated that, under the condition of high initial water pressure and adequate groundwater recharge, to achieve the desired water shut-off effect, the permeability coefficient of grouting circle should be less than that of surrounding rock over one quantitative grade; the water pressure of lining decreased with the increase of discharge, and showed a linear relationship; the lining could meet the requirement on the design water pressure load, when the permeability coefficient of grouting circle less than 1/20 of the surrounding rock’s, and the controlled discharge greater than or equal 1/2 of uncontrolled discharge; the full-sealing waterproof lining would sustain initial water pressure and the calculation value of water pressure couldn’t be discounted, if the grouting wasn’t waterproof.

scholarly journals Designing robust chitosan-based hydrogels for stem cell nesting under oxidative stress

Bioimpacts ◽  
2021 ◽  
Author(s):  
Zahra Olfat Noubari ◽  
Asal Golchin ◽  
Marziyeh Fathi ◽  
Ailar Nakhlband
Keyword(s):  
Oxidative Stress ◽  
Tissue Engineering ◽  
Stem Cells ◽  
Porous Structure ◽  
High Water ◽  
High Water Content ◽  
Dapi Staining ◽  
Antioxidant Genes ◽  
Wide Range ◽  
The Impact

Introduction: Hydrogels are unique candidates for a wide range of biomedical applications including drug delivery and tissue engineering. The present investigation was designed to consider the impact of chitosan-based hydrogels as a scaffold on the proliferation of human bone marrow mesenchymal stem cells (hBM-MSCs) besides neutralization of oxidative stress in hBM-MSCs. Methods: Chitosan (CS) and CS-gelatin hydrogels were fabricated through ionic crosslinking using β-glycerophosphate. The hBM-MSCs were cultured on the prepared matrices and their proliferation was evaluated using DAPI staining and MTT assay. Furthermore, the effect of hydrogels on oxidative stress was assessed by measuring the expression of NQO1, Nrf2, and HO-1 genes using real-time PCR. Results: The developed hydrogels indicated a porous structure with high water content. The toxicity studies showed that the prepared hydrogels have a high biocompatibility/cytocompatibility. The expression of intracellular antioxidant genes was studied to ensure that stress is not imposed by the scaffold on the nested cells. The results showed that Nrf2 as a super transcription factor of antioxidant genes and its downstream antioxidant gene, NQO1 were downregulated. Unexpectedly, the upregulation of HO-1 was detected in the current study. Conclusion: The prepared CS-based hydrogels with desired properties including porous structure, high swelling ability, and cytocompatibility did not show oxidative stress for the nesting of stem cells. Therefore, they could be attractive scaffolds to support stem cells for successful tissue engineering purposes.

scholarly journals Impact of freeze–thaw cycles on soil structure and soil hydraulic properties

SOIL ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 179-191
Author(s):  
Frederic Leuther ◽  
Steffen Schlüter
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Structure ◽  
Hydraulic Properties ◽  
Initial Structure ◽  
Soil Hydraulic Properties ◽  
Freeze Thaw ◽  
Frost Action ◽  
Unsaturated Hydraulic Conductivity ◽  
Soil Hydraulic ◽  
The Impact

Abstract. The ploughing of soils in autumn drastically loosens the soil structure and, at the same time, reduces its stability against external stresses. A fragmentation of these artificially produced soil clods during wintertime is often observed in areas with air temperatures fluctuating around the freezing point. From the pore perspective, it is still unclear (i) under which conditions frost action has a measurable effect on soil structure, (ii) what the impact on soil hydraulic properties is, and (iii) how many freeze–thaw cycles (FTCs) are necessary to induce soil structure changes. The aim of this study was to analyse the cumulative effects of multiple FTC on soil structure and soil hydraulic properties for two different textures and two different initial structures. A silt clay with a substantial amount of swelling clay minerals and a silty loam with fewer swell/shrink dynamics were either kept intact in undisturbed soil cores taken from the topsoil from a grassland or repacked with soil clods taken from a ploughed field nearby. FTCs were simulated under controlled conditions and changes in pore structure ≥ 48 µm were regularly recorded using X-ray µCT. After 19 FTCs, the impact on hydraulic properties were measured, and the resolution of structural characteristics were enhanced towards narrow macropores with subsamples scanned at 10 µm. The impact of FTC on soil structure was dependent on the initial structure, soil texture, and the number of FTCs. Frost action induced a consolidation of repacked soil clods, resulting in a systematic reduction in pore sizes and macropore connectivity. In contrast, the macropore systems of the undisturbed soils were only slightly affected. Independent of the initial structure, a fragmentation of soil clods and macro-aggregates larger than 0.8 to 1.2 mm increased the connectivity of pores smaller than 0.5 to 0.8 mm. The fragmentation increased the unsaturated hydraulic conductivity of all treatments by a factor of 3 in by a factor of 3 in a matrix potential range of −100 to −350 hPa, while water retention was only slightly affected for the silt clay soil. Already 2 to 5 FTCs enforced a well-connected pore system of narrow macropores in all treatments, but it was steadily improved by further FTCs. The implications of fewer FTCs during milder winters caused by global warming are twofold. In ploughed soils, the beneficial seedbed consolidation will be less intense. In grassland soils, which have reached a soil structure in dynamic equilibrium that has experienced many FTCs in the making, there is still a beneficial increase in water supply through increasing unsaturated hydraulic conductivity by continued FTCs that might also be less efficient in the future.

scholarly journals Impact of Number of Segmented Tissues on SAR Prediction Accuracy in Deep Pelvic Hyperthermia Treatment Planning

Cancers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2646
Author(s):  
Iva VilasBoas-Ribeiro ◽  
Gerard C. van Rhoon ◽  
Tomas Drizdal ◽  
Martine Franckena ◽  
Margarethus M. Paulides
Keyword(s):  
Treatment Planning ◽  
High Water ◽  
Specific Model ◽  
Treatment Quality ◽  
Patient Specific ◽  
High Water Content ◽  
Treatment Optimization ◽  
Hyperthermia Treatment ◽  
Pre Treatment ◽  
The Impact

In hyperthermia, the general opinion is that pre-treatment optimization of treatment settings requires a patient-specific model. For deep pelvic hyperthermia treatment planning (HTP), tissue models comprising four tissue categories are currently discriminated. For head and neck HTP, we found that more tissues are required for increasing accuracy. In this work, we evaluated the impact of the number of segmented tissues on the predicted specific absorption rate (SAR) for the pelvic region. Highly detailed anatomical models of five healthy volunteers were selected from a virtual database. For each model, seven lists with varying levels of segmentation detail were defined and used as an input for a modeling study. SAR changes were quantified using the change in target-to-hotspot-quotient and maximum SAR relative differences, with respect to the most detailed patient model. The main finding of this study was that the inclusion of high water content tissues in the segmentation may result in a clinically relevant impact on the SAR distribution and on the predicted hyperthermia treatment quality when considering our pre-established thresholds. In general, our results underline the current clinical segmentation protocol and help to prioritize any improvements.

Long-Term Performance Study of High Moisture Content Cohesive Soil Subgrade in Seasonal Frozen Region

2013 ◽  
Vol 405-408 ◽  
pp. 49-56
Author(s):  
Sheng Chuan Liu ◽  
Gui Ling Ding ◽  
Gang Chen
Keyword(s):  
Theoretical Analysis ◽  
Water Content ◽  
High Water ◽  
High Water Content ◽  
Test Field ◽  
Frozen Ground ◽  
Freeze Thaw ◽  
Long Term Performance ◽  
Term Performance

This project is aiming at the high water content clay in seasonally frozen ground region, based on the expressway program in Heilongjiang province. By applying laboratory test, field test, field monitoring and theoretical analysis, research has been proposed to understand the deformation law and long-term performance of high water content clay subgrade in freeze-thaw condition. From the comparison test of soil and soil treated with lime, road properties of high water content clay has been found out. It is a very necessary and effective method using lime to treat the high water content clay in subgrade construction. Laboratory freeze-thaw experiments uncover the strength weakening law of soil treated with lime. With theoretical analysis and numerical calculation, the interaction between clayey subgrade and pavement structure layer under effect of vehicle dynamic load is analyzed. According to this result, control standards of subgrade frost heave in seasonally frozen ground region and subgrade resilience modulus in spring have been proposed.

scholarly journals Geotechnical properties of sewage sludge solidified with Sulphoaluminate cement

2019 ◽  
Vol 81 ◽  
pp. 01015 ◽  
Author(s):  
Xihui Fan ◽  
Haoqing Xu ◽  
Shengwei Wang ◽  
Shi Shu ◽  
Naixi Lin ◽  
...  
Keyword(s):  
Sewage Sludge ◽  
Construction Material ◽  
High Water ◽  
Organic Soil ◽  
Geotechnical Properties ◽  
High Water Content ◽  
Atterberg Limit ◽  
Sulphoaluminate Cement ◽  
The Impact ◽  
Landfill Disposal

The geotechnical properties of sewage sludge solidified with sulphoaluminate cement are presented. The sludge has a high water content and organic matter which is not easy to disposal. After Solidification/Stabilization (S/S), landfill disposal of sewage sludge is widely adopted in China. However, there is little research focused on the geotechnical properties of sewage sludge after S/S treatment and the impact on the landfill site is also difficult to be evaluated. To solve this problem, this paper is aimed to evaluate the basic mechanics properties of solidified materials by means of Atterberg limit, triaxial test, consolidation test and permeability test. The result showed that the strength and the hydraulic conductivity of the modified sludge was close to that of the high organic soil. By adding suitable additives, modified sludge could not only satisfy the requirement of being landfilled but also be utilized as a construction material.

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