Academic literature on the topic 'Drying-wetting process'
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Journal articles on the topic "Drying-wetting process"
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Sutrisno, Wahyuniarsih, Priyo Suprobo, Endah Wahyuni, and Data Iranata. "Experimental Test of Chloride Penetration in Reinforced Concrete Subjected to Wetting and Drying Cycle." Applied Mechanics and Materials 851 (August 2016): 846–51. http://dx.doi.org/10.4028/www.scientific.net/amm.851.846.
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Chloride ingress is one of the major causes of durability problems in reinforced concrete structures. This research focused to investigate the chloride penetration process through the concrete subjected to wetting and drying cycle. This research used 150 x 150 mm normal concrete prism sample with a 40 mm concrete cover. Three wetting and drying configurations used in this study to investigate the effect of wetting and drying period to the chloride penetration. The result indicated that the chloride concentration and penetration depth were highly influenced by the duration of wetting and drying. Based on the experimental result, concrete exposed to 5 hours drying and 3 hours wetting has the highest chloride concentration compared with the sample exposed to other wetting and drying configuration.
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Meng, Bo, Hongwen Jing, Wenxin Zhu, and Haijian Su. "Influences of Saturation and Wetting-Drying Cycle on Mechanical Performances of Argillaceous Limestones from Liupanshan Tunnel, China." Advances in Materials Science and Engineering 2019 (August 8, 2019): 1–10. http://dx.doi.org/10.1155/2019/9236172.
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Water-rock interaction is a vital factor to affect the stabilities of rock projects. This paper conducted a series of experiments on argillaceous limestones to investigate the influences of saturation and wetting-drying cycle on the physical and mechanical performances of rocks. The results show that the increasing saturation increases the dissolution of clay minerals and lubrication among mineral grains, resulting in an obvious reduction effect on the strength and deformation performances of argillaceous limestones. Wetting-drying cycle increases the porosity and changes the pore structure of argillaceous limestones, leading to the pore transformation from small pore (0.01∼0.1 μm) to relatively large pore (0.1∼1.0 μm). Both the physical and mechanical performances of argillaceous limestones are weakened by the wetting-drying cycle. Besides, the variation process of the physical and mechanical parameters, including mass loss, density, ultrasonic velocity, compression strength, peak strain, elasticity modulus, and secant modulus, can be divided into two stages: 0∼6th wetting-drying cycle, gently changing, and 6th∼12th wetting-drying cycle, drastically changing. The whole change process of these physical and mechanical parameters with the increase in the wetting-drying cycle number can be expressed with the exponential function in general.
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Du, Bin, Wu Sun, and Qiangqiang Cheng. "Influence of Drying-Wetting Cycles on Dynamic Tensile Properties of Red-Sandstone Using the Brazilian Test." Advances in Materials Science and Engineering 2023 (February 20, 2023): 1–12. http://dx.doi.org/10.1155/2023/8330326.
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The phenomenon of the drying-wetting cycle is a component of the weathering process and has a significant impact on the characteristics of rock materials. In order to examine the physical and dynamic tensile properties of red sandstone subjected to drying-wetting cycles, physical tests and dynamic splitting tensile tests were performed on red sandstone specimens under varying drying-wetting conditions. First, the split Hopkins pressure bar was used to perform dynamic tensile tests on red sandstone samples after varying numbers of drying-wetting cycles (0, 20, 40, 60, and 80). Second, the effects of the loading rate and drying-wetting cycles on dynamic tensile strength and energy dissipation of red sandstone were studied. Finally, taking into account the effect of the loading rate, a model was developed to predict the trend of decay in the dynamic tensile strength of red sandstone following drying-wetting cycles. The findings indicate that as the number of drying-wetting cycles increases, there is a decrease in longitudinal wave velocity and a marked degradation of the red sandstone due to the effects of the drying-wetting cycles. The dynamic tensile strength and dissipation energy density of red sandstone samples increase with the increasing loading rate. Under consistent loading rate conditions, the dynamic tensile strength and dissipative energy density of red sandstone samples exhibit a decrease as the number of drying-wetting cycles increases.
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Bang, Van Son, Yi Wang, Trong Vu, et al. "The Influence of Rainfall and Evaporation Wetting–Drying Cycles on the Open-Pit Coal Mine Dumps in Cam Pha, Quang Ninh Region of Vietnam." Applied Sciences 14, no. 5 (2024): 1711. http://dx.doi.org/10.3390/app14051711.
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Among the slope hazards caused by rainfall, not all of them occur directly during storm washout, and the wetting–drying cycles’ effect on the rainfall–evaporation process is an important cause of shallow slope instability. In this study, taking the slope of the open-pit coal mine dumps in Cam Pha, in the Quang Ninh region of Vietnam, as the research object, we carry out experiments on the physical properties of the rock body under different wetting–drying cycles, as well as numerical analyses. The results show that the wetting–drying cycles significantly affect the physical and mechanical parameters and permeability of the rock body. In the process of the wetting–drying cycle, a transient saturated zone occurs on the surface of the slope, and the range of the unsaturated zone inside the slope body decreases with the increase in the number of wetting–drying cycles. Moreover, the infiltration line keeps moving downward, but the rate of downward movement is slowed down by the decrease in the gradient of matrix suction affected by rainfall. Under the influence of the wetting–drying cycles, the slope displacement, plastic zone, and maximum shear strain increment range gradually approach the slope surface with the wetting–drying cycles, and the displacement peak gradually increases. A dump is a site for the centralized discharge of mining waste, formed by the crushing and stockpiling of the original rock formation. Bang Nau is the name of the dump considered in this study. After multiple rainfall events, the slope stability under five wetting–drying cycles decreases from 1.721 to 1.055, and the landslide mode changes from a whole landslide to a single-step shallow landslide, with a certain landslide risk. It is necessary to strengthen the slope stability as the landslide risk is very high, and it is necessary to strengthen the monitoring and inspection of the slope.
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Ye, Hao, Chengfu Chu, Long Xu, Kunlong Guo, and Dong Li. "Experimental Studies on Drying-Wetting Cycle Characteristics of Expansive Soils Improved by Industrial Wastes." Advances in Civil Engineering 2018 (September 24, 2018): 1–9. http://dx.doi.org/10.1155/2018/2321361.
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The improved engineering properties of the expansive soil by mixing with various additives will be changed during the long-term variation of the meteorological and hydrological conditions. In the present work, a series of tests are performed to investigate the evolution of the unconfined compression strength and the Atterberg limits under drying-wetting cycling conditions for specimens treated by iron tailing sands and calcium carbide slag. Typical results of the unconfined compressive strength can be divided into three stages. The unconfined compressive strength increases initially and then decreases to reach a stable state with continuous drying-wetting process. The calcium carbide slag content (αCCS) of 10% can be determined for the minimum effect of the drying-wetting cycle on the strength of the treated specimen. An exponential relationship is established to describe the evolution of the unconfined compressive strength with the drying-wetting cycle. The liquid limit and plastic index of the specimen increase initially followed by a decreasing trend, while a reverse trend was observed for that of the plastic limit during the drying-wetting process. The minimum effect of the drying-wetting cycle on the Atterberg limits can be presented for the specimen with αCCS of 10% as well.
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Jin, Jiayao, and Gang Dai. "Effect of Sterilization on the Change of Available Phosphorus During the Wetting and Drying Process." E3S Web of Conferences 560 (2024): 02015. http://dx.doi.org/10.1051/e3sconf/202456002015.
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Wetting and drying are typical natural events in arid and semiarid areas. In order to explore the contribution of microorganisms to the change in soil phosphorus components during wetting and drying processes, soil incubation experiments were conducted on calcareous soil from Inner Mongolia grasslands. By comparing the change in various phosphorus fractions between sterilized and unsterilized soils, the microbial effect on the change in available phosphorus with soil moisture changes was studied. The results indicated that there was no significant difference in APi (NaHCO3-extractable inorganic phosphate) content between the two treatments. Sterilization caused the content of APo (NaHCO3-extractable inorganic phosphate) to significantly increase. These results suggested that soil microorganisms have a negligible influence on changes of soil available inorganic phosphorus (APi) in the present soil sample during the wetting and drying process. The change in APo may be related to the high-temperature and high-pressure sterilization processes. These results enrich our knowledge about the microbial influence on dynamics of soil available phosphorus during wetting and drying events.
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Yuan, Pu, Ning-Ning Wei, Qin-Yong Ma, and Ju-Cai Chang. "Coupled Effect of Water Temperature and Cyclic Wetting and Drying on Dynamic Mechanical Characteristics of Sandstone." Advances in Civil Engineering 2019 (September 30, 2019): 1–15. http://dx.doi.org/10.1155/2019/8167651.
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Considering the periodical moisture variation in deep rock masses, cyclic wetting and drying under high geothermal condition is a vital issue for the safety and stability of deep rock engineering. To investigate the coupled effect of water temperature and cyclic wetting and drying on dynamic mechanical characteristics of sandstone, dynamic uniaxial compressive tests were carried out under the same loading condition for sandstone specimens subjected to cyclic wetting and drying treatment. When the temperature was 60°C in both wetting and drying processes, cyclic wetting and drying treatment presents a detrimental effect on the tested sandstone. Both physical and dynamic uniaxial compressive characteristics deteriorate in an exponential function with the increase of wetting and drying cycles. Based on SEM image analyses, the initiation and propagation of microcracks is mainly the result of cyclic loading and unloading of tensile stresses induced by water absorption and desorption of kaolinite within sandstone during cyclic wetting and drying treatment. After 15 cycles of wetting and drying, the deterioration of both physical and dynamic uniaxial compressive characteristics first increase then decrease with water temperature in wetting process elevating from 20°C to 98°C. SEM images indicate that more microcracks generate when water temperatures increase from 20°C to 60°C, while the micromorphology is changed and fewer microcracks display due to kaolinite mobilization when water temperature increases from 60°C to 98°C. The threshold value for the effect of water temperature on cyclic wetting and drying is found to be about 60°C for the tested sandstone.
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Wang, Lei, Chunhong Chen, Ronggui Liu, et al. "Chloride Corrosion Process of Concrete with Different Water–Binder Ratios under Variable Temperature Drying–Wetting Cycles." Materials 17, no. 10 (2024): 2263. http://dx.doi.org/10.3390/ma17102263.
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In this paper, four water–binder ratios (w/b) of 0.29, 0.33, 0.39, and 0.46 were designed. A variable test temperature was implemented in the drying–wetting cycle test according to the temperature fluctuations in the actual service environment, and the constant temperature test was established as the control group. The mechanical properties and chloride corrosion resistance of concrete with different w/b ratios under variable temperature drying–wetting cycles, as well as the microstructure changes, phase composition, and damage mechanism inside the concrete, were investigated. The results showed that the mechanical properties of concrete increased first and then decreased with drying–wetting cycles increasing, whereas the chloride corrosion resistance continued to decline. A higher w/b exacerbated the deterioration of the concrete performance. A higher w/b increased the porosity, chloride diffusion depth, and chloride content, thus reducing the resistance of chloride corrosion. Compared with w/b = 0.29, the compressive strength, splitting tensile strength, mass, and relative dynamic elasticity modulus of w/b = 0.46 exposed to 60 drying–wetting cycles decreased by 54.50%, 52.44%, 0.96%, and 6.50%, respectively, while the porosity, peak chloride content, and erosion depth increased by 45.12%, 70.45%, and 45.00%. Compared with the drying–wetting cycle with a constant temperature, the cumulative damage caused by the drying–wetting cycle with a variable temperature was greater, resulting in more severe deterioration of concrete performance. The increase in the test temperature significantly accelerated the diffusion rate, penetration depth, and chemical binding capacity of chloride ions. After 60 drying–wetting cycles, the peak chlorine content and erosion depth of w/b = 0.46 under variable temperature cycles were 15.38% and 10.32% higher than those under a constant temperature, while the compressive strength, splitting tensile strength, mass, and relative dynamic elastic modulus were reduced by 7.76%, 14.81%, 0.33%, and 2.40%, respectively. Microscopic analysis confirmed that higher w/b and variable temperature cycles accelerated the decay of mechanical properties and the decline of chloride corrosion resistance. According to the numerical fitting analysis, the w/b should be 0.29~0.39 under the condition that the mechanical properties and chloride corrosion resistance of concrete are met.
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Kong, Lingwei, Hossain Md Sayem, and Huihui Tian. "Influence of drying–wetting cycles on soil-water characteristic curve of undisturbed granite residual soils and microstructure mechanism by nuclear magnetic resonance (NMR) spin-spin relaxation time (T2) relaxometry." Canadian Geotechnical Journal 55, no. 2 (2018): 208–16. http://dx.doi.org/10.1139/cgj-2016-0614.
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Due to the formational environment and climatic variability, granite residual soils with grain-size distribution ranging from gravel to clay undergo multiple drying–wetting cycles. The influences of multiple drying–wetting cycles on the soil-water characteristic curve (SWCC) and pore-size distribution (POSD) of undisturbed granite residual soils are investigated using the pressure plate test and nuclear magnetic resonance (NMR) spin-spin relaxation time (T2) distribution measurement, respectively. Results show that the water-retention capacity and air-entry value decrease and pores become more uniform with increasing drying–wetting cycles. After four drying–wetting cycles, the soil reaches a nearly constant state. The POSD change of multiple drying–wetting cycle samples is consistent with the SWCC of the soils. Furthermore, a modified van Genuchten model in terms of cumulative pore volume is used to obtain the best-fit POSD of the drying–wetting cycle samples. The shape and changing tendency of both curves of SWCC and POSD are quite similar and achieved a better correlation. It can be concluded that the SWCC is strongly dependent on the POSD of the soil and NMR T2 relaxometry can be used as an alternative to the assessment of microstructural variation of residual soils subjected to the periodic drying and wetting process.
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Guo, Qingzhen, Haijian Su, Hongwen Jing, and Wenxin Zhu. "Effect of Wetting-Drying Cycle on the Deformation and Seepage Behaviors of Rock Masses around a Tunnel." Geofluids 2020 (May 26, 2020): 1–14. http://dx.doi.org/10.1155/2020/4237163.
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Water inrush caused by the wetting-drying cycle is a difficult problem in tunnel excavation. To investigate the effect of the wetting-drying cycle on the stability of the tunnel surrounding rock, physical experiments and numerical simulations regarding the process of tunnel excavation with different wetting-drying cycle numbers were performed in this study. The evolutions of stress, displacement, and pore water pressure were analyzed. With the increase in cycle number, the pore water pressure, vertical stress, and top-bottom approach of the tunnel surrounding rock increase gradually. And the increasing process could be divided into three stages: slightly increasing stage, slowly increasing stage, and sharply increasing stage, respectively. The failure process of the surrounding rock under the wetting-drying cycle gradually occurs from the roof to side wall, while the baseplate changes slightly. The simulation results showed that the maximum principal stress in the surrounding rock mass of the tunnel increases, while the minimum principal stress decreases. Furthermore, the displacement of the rock mass decreases gradually with the increasing distance from the tunnel surface. By comparing the simulation results with the experimental results, well consistency is shown. The results in this study can provide helpful references for the safe excavation and scientific design of a tunnel under the wetting-drying cycle.
Dissertations / Theses on the topic "Drying-wetting process"
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Polatcelik, Remzi Mert. "The assessment of effectiveness and compatibility of water repellents in heritage masonry conservation: laboratory tests and non-destructive investigation through IR thermography." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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Moisture jeopardizes the durability of historic buildings by speeding up the deterioration mechanisms. One way to protect the historic masonry walls from exterior moisture agents is the application of water repellant chemicals. Those chemicals have been used as surface treatments for more than 60 years in historic buildings for conservation purposes. However, most of the time the effectiveness and the performance of the treatments are not evaluated after the onsite application. In this thesis, the evaluation of the effectiveness of those chemicals is investigated through IR thermography and other lab techniques. Small-scale brick samples are used to obtain qualitative and quantitative data to assess the behavior of the brick when it interacts with moisture through capillary action. Moreover, those data are used to compare the results with the thermal image that are obtained from a masonry wall made with the same commercial bricks. These comparisons are aimed to propose a cheap, effective, and continuous monitoring method for the evaluation of the effectiveness of surface treatments for the preservation of historic buildings.
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Chen, Yu-Wen, and 陳昱文. "Amorphous Molybdenum Sulfide Catalyst for Hydrogen Evolution Reaction— Influences of Solution Dynamic Wetting Behavior in The Drying Process." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/bq9daz.
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碩士<br>國立臺灣科技大學<br>化學工程系<br>105<br>Hydrogen is an ideal clean energy, and using the method of water splitting for hydrogen evolution reaction (HER), can prevent the environment from pollution. However, water splitting needs highly efficient catalysts to lower the overpotential. Till today, the most efficient catalyst for HER is still Pt. Therefore, finding a cheap and earth abundant catalyst for HER is essential. Molybdenum sulfide has been proved to be an excellent catalyst for HER.
In this study, the low temperature within atmospheric pressure for thermo-decomposition method to produce amorphous molybdenum sulfide (MoSx) catalyst on carbon paper substrates. However, during the precursor solution drying process, the dynamics of liquid wetting behavior dominates the morphology of MoSx. As a result, here, pairing the substrate hydrophobicity and solvent polarity, the cohesive force between solvent molecules and adhesive force between solvent and carbon paper substrates can be tuned, and thus the MoSx morphology can be controlled.
Pairing hydrophilic carbon paper with DMF+H2O mixing solvent results in a relatively strong adhesive force, it can make the well wrapped MoSx on carbon paper fiber structure. It can lower the charge transfer resistance and boost the current density to 43 mA/cm2 at -0.20 V vs. RHE. Therefore, using DMF+H2O mixing solvent and pair hydrophilic carbon paper can prepare the excellent MoSx catalyst for HER.
Books on the topic "Drying-wetting process"
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Yang, Kun. Observed Regional Climate Change in Tibet over the Last Decades. Oxford University Press, 2017. http://dx.doi.org/10.1093/acrefore/9780190228620.013.587.
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The Tibetan Plateau (TP) is subjected to strong interactions among the atmosphere, hydrosphere, cryosphere, and biosphere. The Plateau exerts huge thermal forcing on the mid-troposphere over the mid-latitude of the Northern Hemisphere during spring and summer. This region also contains the headwaters of major rivers in Asia and provides a large portion of the water resources used for economic activities in adjacent regions. Since the beginning of the 1980s, the TP has undergone evident climate changes, with overall surface air warming and moistening, solar dimming, and decrease in wind speed. Surface warming, which depends on elevation and its horizontal pattern (warming in most of the TP but cooling in the westernmost TP), was consistent with glacial changes. Accompanying the warming was air moistening, with a sudden increase in precipitable water in 1998. Both triggered more deep clouds, which resulted in solar dimming. Surface wind speed declined from the 1970s and started to recover in 2002, as a result of atmospheric circulation adjustment caused by the differential surface warming between Asian high latitudes and low latitudes.The climate changes over the TP have changed energy and water cycles and has thus reshaped the local environment. Thermal forcing over the TP has weakened. The warming and decrease in wind speed lowered the Bowen ratio and has led to less surface sensible heating. Atmospheric radiative cooling has been enhanced, mainly through outgoing longwave emission from the warming planetary system and slightly enhanced solar radiation reflection. The trend in both energy terms has contributed to the weakening of thermal forcing over the Plateau. The water cycle has been significantly altered by the climate changes. The monsoon-impacted region (i.e., the southern and eastern regions of the TP) has received less precipitation, more evaporation, less soil moisture and less runoff, which has resulted in the general shrinkage of lakes and pools in this region, although glacier melt has increased. The region dominated by westerlies (i.e., central, northern and western regions of the TP) received more precipitation, more evaporation, more soil moisture and more runoff, which together with more glacier melt resulted in the general expansion of lakes in this region. The overall wetting in the TP is due to both the warmer and moister conditions at the surface, which increased convective available potential energy and may eventually depend on decadal variability of atmospheric circulations such as Atlantic Multi-decadal Oscillation and an intensified Siberian High. The drying process in the southern region is perhaps related to the expansion of Hadley circulation. All these processes have not been well understood.
Book chapters on the topic "Drying-wetting process"
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Kuwano Reiko, Suwal L.P., and Beltran-Galvis A.L. "Change of physical and mechanical properties of sandy soil due to repeated water infiltration." In Deformation Characteristics of Geomaterials. IOS Press, 2011. https://doi.org/10.3233/978-1-60750-822-9-829.
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This paper presents the deformation characteristics of sandy soil specimens developed in wetting and drying processes. A series of triaxial tests was carried out on Toyoura sand and some silty sands, when the tested material is subject to wetting/drying cycles, under the constant confining pressure of 50kPa. During these processes, small cyclic loading tests were performed in order to obtain small strain stiffness of the materials. Throughout the test, volumetric, axial and radial strains were measured and the amount of water flowing in/out of the specimen was monitored. It was found that the deformation of silty sand was highly affected by the wetting/drying cycles, whereas Toyoura sand did not show noticeable changes. For silty sand, volumetric strains were developed positively throughout the first wetting process as well as the successive drying and repeated drying/wetting stages. The presence of fines appeared to play an important role in collapse behaviour of sandy soil, even though the fines content was only 3%. Small strain stiffness seemed to be also affected by the wet/dry condition, but the change in small strain stiffness could not be well explained by the change of density and suction of the material, which indicates that the internal structure of the material was altered due to the collapse occurred in the first wetting cycle.
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Gullà G., Mandaglio M.C., and Moraci N. "Influence of degradation cycles on the mechanical characteristics of natural clays." In Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2005. https://doi.org/10.3233/978-1-61499-656-9-2521.
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On low depths, soils are exposed seasonally to frequent wetting-drying and freezing-thawing cycles; the degradation effects of these cycles are more pronounced in clayey soils. The number of cycles is due to periods of rainfall and variations in air temperature. Such processes can trigger shallow instability essentially controlled by the physical weathering of soils. An experimental study was carried out to investigate how the physical weathering, reproduced by laboratory wetting-drying and freezing-thawing cycles, affects the mechanical behaviour of natural clays in the superficial layers. For this purpose block samples of Pliocene clays were taken from a slope in Southern Calabria (Italy). They are overconsolidated stiff clays which can be classified as to high plasticity clays (CH). Different specimens were trimmed from the block samples and they were subjected to different numbers of wetting-drying-freezing-thawing cycles and then tested in oedometer and direct shear tests. Results of oedometer and direct shear tests seem to show that the physical weathering has caused a degradation of the bonding due to an insufficient ability to resist this cyclic process. The variations of peak shear strength are pronounced in the first month then they may be regarded as essentially constant. The wetting-drying-freezing-thawing cycles also cause a decrease in compression index and an increase of swelling index.
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Chittoori B.S., Puppala A.J., Saride S., Nazarian S., and Hoyos L.R. "Durability studies of lime stabilized clayey soils." In Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2009. https://doi.org/10.3233/978-1-60750-031-5-2208.
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The proper selection of type and concentration of the stabilization of a soil should consider the complex interaction between the mineralogy of the materials and additives, the presence or absence of moisture in soils and the long-term durability of the stabilization process. One measure of the durability of a stabilized material is to study the strength and volumetric strain potentials of the treated material by subjecting them to different wetting and drying cycles. In this research, two clays with known plasticity characteristics were considered. Stabilizer design was first performed based on strength and pH criterion. At these designed stabilizer dosage levels, samples were prepared and subjected to durability related wetting and drying cycles. At select cycles, mechanical tests including volume change measurements and strength tests were performed. Both volumetric stability and strength variations with respect to wetting and drying cycles were then analyzed. Influence of clay mineralogy and its impact on the mechanical performance of treated soils are explained. Importance of clay mineralogy on durability treatments is addressed.
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Li Jinhui and Zhang Limin. "Formation and repeatability of crack network in soil." In Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering. IOS Press, 2009. https://doi.org/10.3233/978-1-60750-031-5-997.
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The formation process and repeatability of desiccation cracks in soils was studied through field surveys. The changes of crack porosity and aperture with drying time and water content were studied. Results show that the process of crack formation can be divided into three distinct stages: initial stage, primary stage, and steady state stage. In the initial stage few cracks appeared with gradually decreasing water content. After a few cracks appeared in the soil, the soil water would evaporate from the crack walls horizontally in addition to the water loss from the ground surface in the vertical direction. Formation of the crack network in this stage took place rather rapidly within one or two days and this was the primary stage. In the steady sate stage, both the crack porosity and crack aperture increased very slowly and tended to reach a steady state. The pattern and locations of the cracks during several wetting-drying cycles were found to be repeatable. Relatively large cracks might still be open at near saturation for a fresh soil experiencing the first few drying-wetting cycles because shrinkage during the first few drying cycles could cause irreversible fabric changes. Small cracks may disappear due to swelling of soil aggregates. However the cracks remained to be potential discontinuities when the crack aperture is not large enough to allow mitigation of soil particles in the cracks so that healing of cracks cannot take place.
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Liu Qiang, Yasufuku Noriyuki, Omine Kiyoshi, and Kobayashi Taizo. "Automatic soil water retention testing system with volume change measurement." In Deformation Characteristics of Geomaterials. IOS Press, 2011. https://doi.org/10.3233/978-1-60750-822-9-447.
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The complete determination of soil water retention curves requires volume to be measured in order to calculate its void ratio and degree of saturation. The volume change of sample during drying and wetting recycles in soil water retention test is obvious and non-ignorable, especially for the soils with deformability. The soil water retention curve is generally superimposed with the volume change of soil matrix. However, in general, traditional apparatus cannot measure the volume change during test process. In this study, a modified experimental system, which can measure and record volume change during test and the whole process of the test can be controlled by computer, is proposed to determine soil water retention curve. The new system has several advantages over existing apparatus: especially, it is fully automated, is capable of determining both wetting and drying characteristics in significantly less time, and is capable of measuring volume change during test using only one sample. This technical note presents the design detail and algorithm of control software. Water retention curves considering volume change are determined for four types of soil, ranging from sandy to silty. The effect of volume change on soil water retention curve is also discussed.
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Kumar, Uttam, Nirmal Kumar, V. N. Mishra, and R. K. Jena. "Soil Quality Assessment Using Analytic Hierarchy Process (AHP)." In Interdisciplinary Approaches to Information Systems and Software Engineering. IGI Global, 2019. http://dx.doi.org/10.4018/978-1-5225-7784-3.ch001.
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Fields with rice-based cropping systems are unique from other wetland or upland soils because they are associated with frequent cycling between wetting and drying under anaerobic and aerobic conditions. This alters the C and N transformations, microbial activities and their diversity, and soil physical properties, depending on the other crop in rotation with rice. This chapter aims to compare the soil quality of vertisols of central plains of Chhattisgarh under rice-wheat and rice-chickpea cropping systems. Soil quality index was developed using analytical hierarchy process (AHP). Five soil quality indicators were selected under minimum datasets including soil organic carbon, mean weight diameter, available water content, available phosphorous and zinc. The results indicated that the rice-chickpea cropping system shows improved soil quality than that of rice-wheat cropping system.
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Rojas, Eduardo. "The Probabilistic Porous-Solid Model." In Towards a Unified Soil Mechanics Theory: The Use of Effective Stresses in Unsaturated Soils (Third Edition). BENTHAM SCIENCE PUBLISHERS, 2022. http://dx.doi.org/10.2174/9789815050356122010007.
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: In the previous chapter, a computational network porous-solid model was developed to simulate the hydraulic behavior of unsaturated soils. However, important computational constraints make this model unpractical. In this chapter, a probabilistic porous-solid model is developed to overcome these constraints. The probabilistic model is an alternative to the use of computational network models and shows important advantages. This model is built from the probability of a certain pore to be filled or remain filled with water during a wetting or drying process, respectively. The numerical results of the probabilistic model are compared with those of the computational network model showing only slight differences. Then the model is validated by making some numerical and experimental comparisons. Finally, a parametric analysis is presented.
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Lopes, Sérgio, Paulo Pinho, Sandra Santos, Nuno Rodrigues, Jorge Raposo, and Domingos Xavier Viegas. "Modelling sorption processes of 10-hour dead Pinus pinaster branches." In Advances in Forest Fire Research 2022. Imprensa da Universidade de Coimbra, 2022. http://dx.doi.org/10.14195/978-989-26-2298-9_185.
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Forest fuel moisture content is an important parameter that determines fire risk and fire behaviour. An accurate prediction of moisture content is therefore of great importance in fire management. In the fire risk period, dead forest fuel moisture content changes mainly by water vapour sorption processes so its knowledge enables the development of predictive fire risk models. In the present work, the adsorption and desorption processes and equilibrium moisture content of 10-hour dead Pinus pinaster branches (diameter between 0.6 cm and 2.5 cm) were described in order to develop a moisture content prediction model for this type of fuels. Laboratorial tests were used to determine sorption curves, timelag and equilibrium moisture content for different sets of air temperature (range between 20°C and 40°C) and relative humidity (range between 10% and 90%). The sorption curves and equilibrium moisture were also modelled with forest fuels and agricultural and food products existing models. Field tests were used to evaluate the sorption and equilibrium moisture content models performance. Dead Pinus pinaster branches were collected in central Portugal through the year 2020 and 2021 on the Portuguese fire risk period (15th May to 15th October) between 12:00h and 13:00h LST. Samples with 0.6 cm to 2.5 cm diameter were collected and transported to laboratory to determine moisture content. The laboratorial drying and wetting curves of dead Pinus pinaster branches (0.6 cm to 2.5 cm diameter) show that they are not pure exponential functions, but with different timelag values until equilibrium is reached. Additionally, the results suggest no significant relationship of the timelag periods with air relative humidity but a dependence with air temperature, showing an increase in the sorption rates with temperature. In terms of sorption curves, Modified Henderson and Pabis model provide the best fitting. For this type of fuels, the representation of EMC values as a function of air relative humidity at constant temperature allowed to obtain a typical sigmoid curve. The EMC values obtained were higher for desorption process than for adsorption process, indicated the typical hysteresis effect in these processes. It was found that, besides the models used in forest fires, other EMC models are also suitable to predict fuel moisture content of dead Pinus pinaster branches, as the ones used in agricultural and food analysis.
Conference papers on the topic "Drying-wetting process"
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Legat, A., V. Kuhar, M. Leban, and A. Vernekar. "Comparison between Electrochemical Noise and Measurements with Electrical Resistance Probes in Concrete." In CORROSION 2003. NACE International, 2003. https://doi.org/10.5006/c2003-03390.
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Abstract In the study two different methods were used to monitor corrosion of steel embedded in concrete. Electrochemical noise and electrical resistance techniques are frequently used in various industrial fields, especially in the oil and chemical-processing industry, but very rarely in concrete structures. Both techniques were slightly modified and tested in carbonated concrete specimens during successive wetting (exposure to salt water) and drying cycles. The results of the measurements were compared with the results of corrosion assessments of the rebars after the specimens were disintegrated. It was confirmed that both methods are effective for measuring corrosion of steel embedded in concrete, and somehow compatible. Electrochemical noise technique can detect various stages of the corrosion process (the initiation of corrosion, dynamic behaviour of corrosion during wetting and drying of concrete), whereas electrical resistance probes indicate cumulative corrosion damage. The results of both methods indicated also some general characteristics of corrosion processes in concrete.
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Matsuoka, K., H. Kihira, S. Ito, and T. Murata. "Monitoring of Corrosion of Reinforcing Bar in Concrete." In CORROSION 1987. NACE International, 1987. https://doi.org/10.5006/c1987-87121.
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Abstract The purpose of this study is to make clear fundamental aspect of the corrosion behavior of reinforcing steel bars in concrete, and to develop an accurate monitoring method. In order to simulate the corrosion environment of concrete structures, a cyclic wetting and drying test in artificial synthetic sea water was conducted using the samples of steel plates embedded in mortar. The samples were monitored by A.C. impedance method for a month or so during the tests. The following conclusions were obtained in this study. From the impedance study of the corrosion of steel in mortar, the corrosion reaction can be explained by the equivalent circuit represented as a parallel combination of anodic reaction resistance and cathodic one controlled by diffusion.The corrosion process of steel in concrete can be classified into three stages: (a) The first stage: passive film on steel surface is stable. (b) The second stage: passive film is partially broken down by chloride attack. The corrosion reaction is controlled by oxygen diffusion, where oxygen concentration is then reduced upon wetting but increased in drying, and (c) The third stage: the corrosion reaction is controlled by redox reaction of ferric ion within rust layers formed around reinforcing bars.Utilization of both A.C. impedance and rest potential measurements give a very useful and accurate tool to monitor the corrosion of reinforcing bars in concrete structures.
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Stuart, Charles O., and Charles Vallance. "Underwater Inspection and Repair of Linings in Immersion Areas." In CORROSION 1988. NACE International, 1988. https://doi.org/10.5006/c1988-88176.
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Abstract Periodic condition evaluation of in-service coatings and linings is the most cost effective method of assuring that minor defects are repaired before major maintenance is required. Repairing minor defects in the early stages of corrosion results in extending the life of the coating system at minimum cost. Periodic condition evaluations of linings in immersion service presents unique problems. The contents of the tank must be used or stored elsewhere. The tank must be cleaned prior to inspection. The inspection process in the dry requires, at a minimum, foot traffic on the coating and frequently scaffolding to reach upper areas. This process often results in additional damage to a lining system which has been embrittled by wetting and drying. This paper will present a proven system of underwater cleaning, inspection and repair of immersed lining systems. Underwater inspection and repair can and is accomplished in contaminated liquids ranging from chemicals to radiologically contaminated water. Inspections are documented photographically and with video presentations. The paper will also discuss completed projects, project safety, scheduling, client support, documentation and costs.
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John, R. C., and W. Van Hooff. "Improved Corrosion Control by Coating in the Splash Zone and Subsea." In CORROSION 1988. NACE International, 1988. https://doi.org/10.5006/c1988-88456.
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Abstract The splash zone around offshore structures is without doubt one of nature’s most hostile and corrosive environments. Apart from the continuous wetting and drying of salt spray, wave impacts, plentiful supplies of oxygen and lack of cathodic protection, the region is always difficult and sometimes dangerous to access. This paper reviews the performance of two new offshore repair coatings recently installed on North Sea and Gulf of Mexico installations. The first coating, a reinforced heatshrinkable sleeve, is designed to be installed over properly cleaned and dried steel surfaces. Suitable conditions for the application of this coating exist during low tide and calm weather when certain exposed sections of the splash zone are accessible. Alternatively, by using a special remote controlled cofferdam chamber to create an artificial local environment, subsea coating application can proceed under ideal conditions. Cofferdam chamber installations are diver-free and can be made throughout the entire splash zone, even during rough weather. When a remote controlled cofferdam is not available and repairs are needed in subsea or wet areas, then some form of diver assistance is usually required. The second coating system, a unique gel-based, diver applied tape has been developed specifically for such applications.
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Taranto, Osvaldir Pereira, R. F. Nascimento, K. Andreola, and J. G. Rosa. "Improvement of pea protein isolate powder properties by agglomeration in a fluidized bed: comparison between binder solutions." In 21st International Drying Symposium. Universitat Politècnica València, 2018. http://dx.doi.org/10.4995/ids2018.2018.7344.
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This study aimed to compare the agglomeration process of pea protein isolate (PPI) using water and aqueous gum Arabic solution as binder liquids. Drying air temperature and binder flow rate were set at 75 °C and 3.1 mL/min, respectively. Moisture content, mean particle size, wetting time and flowability were analyzed. Using water as binder liquid, the responses were (4.0 ± 0.4)%, 316.13 ± 16.73 μm, 10 s and free flow, respectively. Aqueous gum Arabic solution provided (2.9 ± 0.5)%, 462.67 ± 51.23 μm, 3 s and free flow as responses. Gum Arabic solution showed to be a more promising binder.Keywords: Agglomeration; Pulsed fluidized bed; Pea protein isolate; Wetting time; Flowability
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Sham, J. F. C., W. W. L. Lai, and C. H. C. Leung. "Effects of homogeneous/heterogeneous water distribution on GPR wave velocity in a soil's wetting and drying process." In 2016 16th International Conference on Ground Penetrating Radar (GPR). IEEE, 2016. http://dx.doi.org/10.1109/icgpr.2016.7572693.
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"Degradation Process of Cementitious Materials with Copper Slag Subjected to Sodium Sulfate Attack under Drying-Wetting Cycles." In "SP-330: Recent Advances in Concrete Technology and Sustainability Issues Proceedings Fourteenth International Conference Beijing, China". American Concrete Institute, 2018. http://dx.doi.org/10.14359/51711235.
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Tohm, Calvin, and Bret Lingwall. "Shear Strength and 1D Compressibility Characteristics of a Plastic and Non-Plastic Soil Exposed to Wet-Dry Weathering." In 58th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2024. http://dx.doi.org/10.56952/arma-2024-0433.
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ABSTRACT: Seasonal weathering cycles such as wet-dry desiccation weathering can alter geomaterial (weak rock to soil) structure, particle arrangement (i.e. fabric), shear strength, 1D compressibility, and other engineering properties. During the drying and rehydration process associated with wet-dry weathering cycles geomaterial intra-particle forces are altered. These micro-scale changes to rock structure and soil fabric facilitate macro-scale responses in the soils engineering properties. As the number of wetting-drying cycles increases its expected to see the geomaterial mass become fragmented and disjointed due to the formation of drying tensile cracks. Upon rewetting the tensile cracks within the soil mass may partially recover but will still result in altered soil properties. This study sought to investigate how this phenomenon alters a soils shear strength and 1D compressibility properties. To accomplish this a plastic (MH) weathered shale residual and non-plastic (SC) soil was molded at its optimum moisture content (OMC) in accordance with ASTM D698 then exposed to 0, 1, 2, and 10 wetting-drying cycles. It was found that the wetting-drying cycles had a large impact on the MH material. This is most likely a result of the higher swelling clay content in the MH material, resulting in larger amounts of shrink swell that occurring during drying and rehydration of the samples. The SC soil contained relatively little amounts of swelling clay which resulted in smaller amounts of sample alteration that occurred during the weathering cycles. 1. INTRODCUTION Seasonally driven weathering cycles act as external environmentally driven stresses on near surface soil, rock and intermediary geomaterial (IGM) masses. Seasonal weathering cycles gradually alter geomaterial engineering properties by gradually degrading the material fabric. Seasonal weathering cycles (freeze-thaw and wetting-drying desiccation) interact with the topmost layer of soil or rock in the upper 2 to 5-m and develop an active zone in this depth range in the slope as the degree of weathering over time increase. This ultimately results in degraded soil, weak rock or IGM that becomes fragmented and disjointed at the degree of degradation increases unless repaired through mechanical compaction, grouting, or anchoring.
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Reineke, Lea, Regina Schlegel, and Sebastian Hein. "Influence Of Powder Packing Density On Binder Saturation And Wetting Behavior In Metal Binder Jetting." In Euro Powder Metallurgy 2023 Congress & Exhibition. EPMA, 2023. http://dx.doi.org/10.59499/ep235740488.
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Metal Binder Jetting (MBJ) has an increasing attention in additive manufacturing because of its serial production potential. Finding the most suitable parameterization in MBJ and develop pre-printing tests, can reduce the iteration stages in material-specific process development, which saves costs, effort as well as material resources and printing capacity. The powder binder interaction of five powders at different packing densities were determined and the wetting behaviors were compared. The equilibrium saturation, the wetting rate and the initial wetting time were analyzed. In order to understand the nature of the resulting porosity at low packing density, various samples were sintered and compared by micrographs. The results show that an increasing packing density decreases the initial wetting time, increases the equilibrium saturation and lowers the saturation rate. The relationship between wetting behavior and printing parameters, as well as the effect of drying must be investigated further in subsequent studies.
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Reineke, Lea, Regina Schlegel, and Sebastian Hein. "Influence Of Binder Characteristics On Binder Saturation And Wetting Behavior In Metal Binder Jetting." In Euro Powder Metallurgy 2024 Congress & Exhibition. EPMA, 2024. http://dx.doi.org/10.59499/ep246233737.
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Metal Binder Jetting (MBJ) has an increasing attention in Additive Manufacturing because of its serial production potential. The aim of this work is to get a better understanding of the powder-binder-interaction for better process control and consequently a reduction in the number of iteration stages in material-specific process development, which saves costs, effort as well as material resources and printing capacity. Depending on the binder characteristics, the equilibrium saturation and wetting behavior changes. A better understanding of binder viscosity and surface tension on the powder-binder-interaction will improve the part quality. A suitable parameterization of the MBJ printing processes for specific powder-binder combinations, based on the binder and powder characteristics as well as the powder-binder interaction will improve the part density, accuracy and surface quality. The results show that, depending on the binder characteristics, the equilibrium saturation and wetting behavior changes. A higher surface tension seems to cause a higher equilibrium saturation and a lower saturation rate. The effect of the surface tension on the initial wetting time was overlaid by the effect of the surface chemistry. A higher viscosity leads to a significant higher initial wetting time on the powder bed surface, significant higher equilibrium saturation and a significant lower saturation rate. The relationship between wetting behavior and printing parameters as well as the effect of drying and droplet impact must be investigated further in subsequent studies.
Reports on the topic "Drying-wetting process"
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Snyder, Victor A., Dani Or, Amos Hadas, and S. Assouline. Characterization of Post-Tillage Soil Fragmentation and Rejoining Affecting Soil Pore Space Evolution and Transport Properties. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7580670.bard.
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Tillage modifies soil structure, altering conditions for plant growth and transport processes through the soil. However, the resulting loose structure is unstable and susceptible to collapse due to aggregate fragmentation during wetting and drying cycles, and coalescense of moist aggregates by internal capillary forces and external compactive stresses. Presently, limited understanding of these complex processes often leads to consideration of the soil plow layer as a static porous medium. With the purpose of filling some of this knowledge gap, the objectives of this Project were to: 1) Identify and quantify the major factors causing breakdown of primary soil fragments produced by tillage into smaller secondary fragments; 2) Identify and quantify the. physical processes involved in the coalescence of primary and secondary fragments and surfaces of weakness; 3) Measure temporal changes in pore-size distributions and hydraulic properties of reconstructed aggregate beds as a function of specified initial conditions and wetting/drying events; and 4) Construct a process-based model of post-tillage changes in soil structural and hydraulic properties of the plow layer and validate it against field experiments. A dynamic theory of capillary-driven plastic deformation of adjoining aggregates was developed, where instantaneous rate of change in geometry of aggregates and inter-aggregate pores was related to current geometry of the solid-gas-liquid system and measured soil rheological functions. The theory and supporting data showed that consolidation of aggregate beds is largely an event-driven process, restricted to a fairly narrow range of soil water contents where capillary suction is great enough to generate coalescence but where soil mechanical strength is still low enough to allow plastic deforn1ation of aggregates. The theory was also used to explain effects of transient external loading on compaction of aggregate beds. A stochastic forInalism was developed for modeling soil pore space evolution, based on the Fokker Planck equation (FPE). Analytical solutions for the FPE were developed, with parameters which can be measured empirically or related to the mechanistic aggregate deformation model. Pre-existing results from field experiments were used to illustrate how the FPE formalism can be applied to field data. Fragmentation of soil clods after tillage was observed to be an event-driven (as opposed to continuous) process that occurred only during wetting, and only as clods approached the saturation point. The major mechanism of fragmentation of large aggregates seemed to be differential soil swelling behind the wetting front. Aggregate "explosion" due to air entrapment seemed limited to small aggregates wetted simultaneously over their entire surface. Breakdown of large aggregates from 11 clay soils during successive wetting and drying cycles produced fragment size distributions which differed primarily by a scale factor l (essentially equivalent to the Van Bavel mean weight diameter), so that evolution of fragment size distributions could be modeled in terms of changes in l. For a given number of wetting and drying cycles, l decreased systematically with increasing plasticity index. When air-dry soil clods were slightly weakened by a single wetting event, and then allowed to "age" for six weeks at constant high water content, drop-shatter resistance in aged relative to non-aged clods was found to increase in proportion to plasticity index. This seemed consistent with the rheological model, which predicts faster plastic coalescence around small voids and sharp cracks (with resulting soil strengthening) in soils with low resistance to plastic yield and flow. A new theory of crack growth in "idealized" elastoplastic materials was formulated, with potential application to soil fracture phenomena. The theory was preliminarily (and successfully) tested using carbon steel, a ductile material which closely approximates ideal elastoplastic behavior, and for which the necessary fracture data existed in the literature.
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Chapman, Ray, Phu Luong, Sung-Chan Kim, and Earl Hayter. Development of three-dimensional wetting and drying algorithm for the Geophysical Scale Transport Multi-Block Hydrodynamic Sediment and Water Quality Transport Modeling System (GSMB). Engineer Research and Development Center (U.S.), 2021. http://dx.doi.org/10.21079/11681/41085.
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The Environmental Laboratory (EL) and the Coastal and Hydraulics Laboratory (CHL) have jointly completed a number of large-scale hydrodynamic, sediment and water quality transport studies. EL and CHL have successfully executed these studies utilizing the Geophysical Scale Transport Modeling System (GSMB). The model framework of GSMB is composed of multiple process models as shown in Figure 1. Figure 1 shows that the United States Army Corps of Engineers (USACE) accepted wave, hydrodynamic, sediment and water quality transport models are directly and indirectly linked within the GSMB framework. The components of GSMB are the two-dimensional (2D) deep-water wave action model (WAM) (Komen et al. 1994, Jensen et al. 2012), data from meteorological model (MET) (e.g., Saha et al. 2010 - http://journals.ametsoc.org/doi/pdf/10.1175/2010BAMS3001.1), shallow water wave models (STWAVE) (Smith et al. 1999), Coastal Modeling System wave (CMS-WAVE) (Lin et al. 2008), the large-scale, unstructured two-dimensional Advanced Circulation (2D ADCIRC) hydrodynamic model (http://www.adcirc.org), and the regional scale models, Curvilinear Hydrodynamics in three dimensions-Multi-Block (CH3D-MB) (Luong and Chapman 2009), which is the multi-block (MB) version of Curvilinear Hydrodynamics in three-dimensions-Waterways Experiments Station (CH3D-WES) (Chapman et al. 1996, Chapman et al. 2009), MB CH3D-SEDZLJ sediment transport model (Hayter et al. 2012), and CE-QUAL Management - ICM water quality model (Bunch et al. 2003, Cerco and Cole 1994). Task 1 of the DOER project, “Modeling Transport in Wetting/Drying and Vegetated Regions,” is to implement and test three-dimensional (3D) wetting and drying (W/D) within GSMB. This technical note describes the methods and results of Task 1. The original W/D routines were restricted to a single vertical layer or depth-averaged simulations. In order to retain the required 3D or multi-layer capability of MB-CH3D, a multi-block version with variable block layers was developed (Chapman and Luong 2009). This approach requires a combination of grid decomposition, MB, and Message Passing Interface (MPI) communication (Snir et al. 1998). The MB single layer W/D has demonstrated itself as an effective tool in hyper-tide environments, such as Cook Inlet, Alaska (Hayter et al. 2012). The code modifications, implementation, and testing of a fully 3D W/D are described in the following sections of this technical note.
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Or, Dani, Shmulik Friedman, and Jeanette Norton. Physical processes affecting microbial habitats and activity in unsaturated agricultural soils. United States Department of Agriculture, 2002. http://dx.doi.org/10.32747/2002.7587239.bard.
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experimental methods for quantifying effects of water content and other dynamic environmental factors on bacterial growth in partially-saturated soils. Towards this end we reviewed critically the relevant scientific literature and performed theoretical and experimental studies of bacterial growth and activity in modeled, idealized and real unsaturated soils. The natural wetting-drying cycles common to agricultural soils affect water content and liquid organization resulting in fragmentation of aquatic habitats and limit hydraulic connections. Consequently, substrate diffusion pathways to soil microbial communities become limiting and reduce nutrient fluxes, microbial growth, and mobility. Key elements that govern the extent and manifestation of such ubiquitous interactions include characteristics of diffusion pathways and pore space, the timing, duration, and extent of environmental perturbations, the nature of microbiological adjustments (short-term and longterm), and spatial distribution and properties of EPS clusters (microcolonies). Of these key elements we have chosen to focus on a manageable subset namely on modeling microbial growth and coexistence on simple rough surfaces, and experiments on bacterial growth in variably saturated sand samples and columns. Our extensive review paper providing a definitive “snap-shot” of present scientific understanding of microbial behavior in unsaturated soils revealed a lack of modeling tools that are essential for enhanced predictability of microbial processes in soils. We therefore embarked on two pronged approach of development of simple microbial growth models based on diffusion-reaction principles to incorporate key controls for microbial activity in soils such as diffusion coefficients and temporal variations in soil water content (and related substrate diffusion rates), and development of new methodologies in support of experiments on microbial growth in simple and observable porous media under controlled water status conditions. Experimental efforts led to a series of microbial growth experiments in granular media under variable saturation and ambient conditions, and introduction of atomic force microscopy (AFM) and confocal scanning laser microscopy (CSLM) to study cell size, morphology and multi-cell arrangement at a high resolution from growth experiments in various porous media. The modeling efforts elucidated important links between unsaturated conditions and microbial coexistence which is believed to support the unparallel diversity found in soils. We examined the role of spatial and temporal variation in hydration conditions (such as exist in agricultural soils) on local growth rates and on interactions between two competing microbial species. Interestingly, the complexity of soil spaces and aquatic niches are necessary for supporting a rich microbial diversity and the wide array of microbial functions in unsaturated soils. This project supported collaboration between soil physicists and soil microbiologist that is absolutely essential for making progress in both disciplines. It provided a few basic tools (models, parameterization) for guiding future experiments and for gathering key information necessary for prediction of biological processes in agricultural soils. The project sparked a series of ongoing studies (at DTU and EPFL and in the ARO) into effects of soil hydration dynamics on microbial survival strategy under short term and prolonged desiccation (important for general scientific and agricultural applications).
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Shani, Uri, Lynn Dudley, Alon Ben-Gal, Menachem Moshelion, and Yajun Wu. Root Conductance, Root-soil Interface Water Potential, Water and Ion Channel Function, and Tissue Expression Profile as Affected by Environmental Conditions. United States Department of Agriculture, 2007. http://dx.doi.org/10.32747/2007.7592119.bard.
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Constraints on water resources and the environment necessitate more efficient use of water. The key to efficient management is an understanding of the physical and physiological processes occurring in the soil-root hydraulic continuum.While both soil and plant leaf water potentials are well understood, modeled and measured, the root-soil interface where actual uptake processes occur has not been sufficiently studied. The water potential at the root-soil interface (yᵣₒₒₜ), determined by environmental conditions and by soil and plant hydraulic properties, serves as a boundary value in soil and plant uptake equations. In this work, we propose to 1) refine and implement a method for measuring yᵣₒₒₜ; 2) measure yᵣₒₒₜ, water uptake and root hydraulic conductivity for wild type tomato and Arabidopsis under varied q, K⁺, Na⁺ and Cl⁻ levels in the root zone; 3) verify the role of MIPs and ion channels response to q, K⁺ and Na⁺ levels in Arabidopsis and tomato; 4) study the relationships between yᵣₒₒₜ and root hydraulic conductivity for various crops representing important botanical and agricultural species, under conditions of varying soil types, water contents and salinity; and 5) integrate the above to water uptake term(s) to be implemented in models. We have made significant progress toward establishing the efficacy of the emittensiometer and on the molecular biology studies. We have added an additional method for measuring ψᵣₒₒₜ. High-frequency water application through the water source while the plant emerges and becomes established encourages roots to develop towards and into the water source itself. The yᵣₒₒₜ and yₛₒᵢₗ values reflected wetting and drying processes in the rhizosphere and in the bulk soil. Thus, yᵣₒₒₜ can be manipulated by changing irrigation level and frequency. An important and surprising finding resulting from the current research is the obtained yᵣₒₒₜ value. The yᵣₒₒₜ measured using the three different methods: emittensiometer, micro-tensiometer and MRI imaging in both sunflower, tomato and corn plants fell in the same range and were higher by one to three orders of magnitude from the values of -600 to -15,000 cm suggested in the literature. We have added additional information on the regulation of aquaporins and transporters at the transcript and protein levels, particularly under stress. Our preliminary results show that overexpression of one aquaporin gene in tomato dramatically increases its transpiration level (unpublished results). Based on this information, we started screening mutants for other aquaporin genes. During the feasibility testing year, we identified homozygous mutants for eight aquaporin genes, including six mutants for five of the PIP2 genes. Including the homozygous mutants directly available at the ABRC seed stock center, we now have mutants for 11 of the 19 aquaporin genes of interest. Currently, we are screening mutants for other aquaporin genes and ion transporter genes. Understanding plant water uptake under stress is essential for the further advancement of molecular plant stress tolerance work as well as for efficient use of water in agriculture. Virtually all of Israel’s agriculture and about 40% of US agriculture is made possible by irrigation. Both countries face increasing risk of water shortages as urban requirements grow. Both countries will have to find methods of protecting the soil resource while conserving water resources—goals that appear to be in direct conflict. The climate-plant-soil-water system is nonlinear with many feedback mechanisms. Conceptual plant uptake and growth models and mechanism-based computer-simulation models will be valuable tools in developing irrigation regimes and methods that maximize the efficiency of agricultural water. This proposal will contribute to the development of these models by providing critical information on water extraction by the plant that will result in improved predictions of both water requirements and crop yields. Plant water use and plant response to environmental conditions cannot possibly be understood by using the tools and language of a single scientific discipline. This proposal links the disciplines of soil physics and soil physical chemistry with plant physiology and molecular biology in order to correctly treat and understand the soil-plant interface in terms of integrated comprehension. Results from the project will contribute to a mechanistic understanding of the SPAC and will inspire continued multidisciplinary research.