In this article, we investigated the influence of size and initial water content on the effective diffusion coefficient of sweet potatoes samples cut into cubic and cylindrical shapes. The sizes of the cubic samples a...In this article, we investigated the influence of size and initial water content on the effective diffusion coefficient of sweet potatoes samples cut into cubic and cylindrical shapes. The sizes of the cubic samples are 0.5, 1, 1.5, 1.75, 2, 2.5 and 3 cm edge with a respective initial water content of 2.7, 3.76, 3.48, 2.68, 3.28, 2.17 and 2.29 kg/kgms. For cylindrical samples, the radius is set at 0.5 cm and sample heights are 1, 1.5, 2, 2.5, 3, 3.5 and 4 cm with respective water contents of 2.2, 3.19, 2.85, 2.1, 2.17, 2.39 and 2.03 kg/kgms. The effective diffusion coefficients of cubic samples are of the order of 10−10 and 10−9 m2∙s−1 grew with sample edge. As for the cylindrical samples, the effective diffusion coefficients were of the order of 10−9 m2∙s−1 and there was no linear correlation between cylinder height and their effective diffusion coefficient. As for the examination of the initial water content on the effective diffusion coefficient, it turned out that the initial water content had no influence on the effective diffusion coefficient of the sweet potato samples.展开更多
The observations on compressibility of reconstituted clays show that the compression line with a higher initial water content lies above the compression line with a lower initial water content for a given clay. Hence ...The observations on compressibility of reconstituted clays show that the compression line with a higher initial water content lies above the compression line with a lower initial water content for a given clay. Hence there exists additional void ratio due to initial water contents among virgin compression lines(VCLs) of reconstituted clays. In this paper, the difference in void ratio caused by different initial water contents is investigated based on the empirical equation proposed by Liu and Carter(2000) for describing the differential void ratio at the same stress between natural and reconstituted clays. The mechanism of compressibility of reconstituted clays, when the stress level is larger than the remolded yield stress, is also discussed.展开更多
The effects of soil texture, initial water content and bulk density on diesel oil infiltration in fine sand and silty clay loam materials were evaluated. Three physical and two empirical equations express diesel oil i...The effects of soil texture, initial water content and bulk density on diesel oil infiltration in fine sand and silty clay loam materials were evaluated. Three physical and two empirical equations express diesel oil infiltration through soils with time, with coefficients of determination greater than 0.99. Diesel oil infiltrates more quickly in the fine sand than in the silty clay loam material. Diesel oil infiltration rates are found to decrease with increasing initial water content and bulk density for the silty clay loam material. The infiltration rate of diesel oil in the fine sand material increases slightly with increasing initial water content. The diesel oil saturated conductivity(Kdiesel) decreases with increasing bulk density for the silty clay loam column. Diesel oil sorptivity(S) decreases linearly with increased initial water content and bulk density of the silty clay loam material. Changes in empirical parameters relative to initial water content and bulk density are similar to the parameter S.展开更多
The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for d...The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for damaging contaminants. It is well known that the capillarity coefficient and sorptivity are two important parameters to characterize the water absorption of porous materials. Generally, the former is used to describe the penetration depth or height of water transport, which must be measured by special and advanced equipment. In contrast, the sorptivity represents the relationship between cumulative volume of water uptake and the squareroot of the elapsed time, which can be easily measured by the gravimetric method in a normal laboratory condition. In the present study, an analytical method is developed to build up a bridge between these two parameters, with the purpose that the sorptivity or the gravimetric method can be used to predict the penetration depth of water absorption. Additionally, a new model to explain the dependence of sorptivity on initial water content of the material is developed in order to fit the in situ condition. The comparison of predicted results by the analytical method with experimental data or numerical calculation results, as well as some previous models, validates the feasibility of the methods presented in this paper.展开更多
The soil-water characteristic curve(SWCC)is often used to estimate unsaturated soil properties(e.g.strength,permeability,volume change,solute and thermal diffusivity).The SWCC of soil samples is significantly affected...The soil-water characteristic curve(SWCC)is often used to estimate unsaturated soil properties(e.g.strength,permeability,volume change,solute and thermal diffusivity).The SWCC of soil samples is significantly affected by cyclic wetting-drying.To examine how water content and cyclic wetting-drying affect the SWCC of disintegrated carbonaceous mudstone(DCM),SWCC tests were implemented using a pressure-plate apparatus.In addition,SWCC models for DCM considering the initial gravimetric water content and cyclic wetting-drying were developed.The test results showed that the volumetric water content(θ)of the DCM first decreased rapidly and then became stable as matric suction(s)increased.The initial water content affected the SWCC by altering the pore structure of the DCM.For a given number of wetting-drying cycles,the higher the initial water content,the higher the stabilizedθ.At a given s value,θdecreased as the number of wetting-drying cycles increased,which suggests that cyclic wetting-drying reduces the water-holding capacity of DCM.The Gardner model for DCM was constructed considering initial water content and cyclic wetting-drying,and was effective at describing and predicting the SWCC model for DCM.展开更多
The compression behavior responsible for unity sensitivity is very valuable in quantitative assessment of the effects of soil structure on the compression behavior of soft marine sediments. However, the quantitative a...The compression behavior responsible for unity sensitivity is very valuable in quantitative assessment of the effects of soil structure on the compression behavior of soft marine sediments. However, the quantitative assessment of such effects is not possible because of unavailability of the formula for the compression curve of marine sediments responsible for unit sensitivity. In this study, the relationship between the remolded state and the conventional critical state line is presented in the deviator stress versus mean effective stress plot. The analysis indicates that the remolded state is on the conventional critical state line obtained at a relatively small strain. Thus, a unique critical state sedimentation line for marine sediments of unit sensitivity is proposed. The comparison between the critical state sedimentation line proposed in this study and the existing normalized consolidation curves obtained from conventional oedometer tests on remolded soils or reconstituted soils explains well the展开更多
To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil w...To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil water content, and tube diameter on the emitter discharge of the vertical tube were studied. The results show that quantitative relationship between the time and cumulative infiltration and emitter discharge of the vertical tube is obtained, and R 2 is more than 0.98. Emitter discharge exhibits a positive and negative correlation with the pressure head and soil water content, respectively. Tube dia- meter has a nonsignificant effect on the emitter discharge. Changes of the soil water content around the emitter water outlet are the main causes of emitter discharge variations. In the experiments, the range of vertical tube emitter discharge is 0.056-1.102 L/h. The emitter of vertical tube irrigation automatically adjusts the soil water content and maintains the root zone soil water content within an appropriate range, which achieves continuous irrigation, and further achieves the effect of water-saving.展开更多
Mulching and soil water content(SWC) have a significant impact on soil erosion,and this study investigated the effect of straw mulching on water infiltration and soil loss under different initial SWC treatments in a r...Mulching and soil water content(SWC) have a significant impact on soil erosion,and this study investigated the effect of straw mulching on water infiltration and soil loss under different initial SWC treatments in a rainfall simulation experiment conducted in northern China.Increasing initial SWC can decrease soil infiltration and increase soil loss.During an 80 mm rainfall event(80 mm·h–1for 60 min),8%,12% and 16% initial SWC treatments decreased cumulative infiltration by8.7%,42.5% and 58.1%,and increased total sediment yield by 44,146 and 315 g,respectively,compared to 4%initial SWC.However,in all the straw mulching treatments,there was no significant difference in stable infiltration rate between the different initial SWC treatments.For all initial SWC treatments,straw mulching of30% or more significantly enhanced water infiltration by over 31% and reduced soil loss by over 49%,compared to the unmulched treatment.Taking into consideration the performance of no-till planters,a maize straw mulching rate of 30% to 60%(1400–3100 kg·hm–2) is recommended for the conservation of water and soil in northern China.展开更多
文摘In this article, we investigated the influence of size and initial water content on the effective diffusion coefficient of sweet potatoes samples cut into cubic and cylindrical shapes. The sizes of the cubic samples are 0.5, 1, 1.5, 1.75, 2, 2.5 and 3 cm edge with a respective initial water content of 2.7, 3.76, 3.48, 2.68, 3.28, 2.17 and 2.29 kg/kgms. For cylindrical samples, the radius is set at 0.5 cm and sample heights are 1, 1.5, 2, 2.5, 3, 3.5 and 4 cm with respective water contents of 2.2, 3.19, 2.85, 2.1, 2.17, 2.39 and 2.03 kg/kgms. The effective diffusion coefficients of cubic samples are of the order of 10−10 and 10−9 m2∙s−1 grew with sample edge. As for the cylindrical samples, the effective diffusion coefficients were of the order of 10−9 m2∙s−1 and there was no linear correlation between cylinder height and their effective diffusion coefficient. As for the examination of the initial water content on the effective diffusion coefficient, it turned out that the initial water content had no influence on the effective diffusion coefficient of the sweet potato samples.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41502263,41372309 and 41330641)the National Key Basic Research Program of China(973 Program,Grant No.2015CB057803)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20150819)the Fundamental Research Funds for the Central Universities of China in support of this study is also gratefully acknowledged
文摘The observations on compressibility of reconstituted clays show that the compression line with a higher initial water content lies above the compression line with a lower initial water content for a given clay. Hence there exists additional void ratio due to initial water contents among virgin compression lines(VCLs) of reconstituted clays. In this paper, the difference in void ratio caused by different initial water contents is investigated based on the empirical equation proposed by Liu and Carter(2000) for describing the differential void ratio at the same stress between natural and reconstituted clays. The mechanism of compressibility of reconstituted clays, when the stress level is larger than the remolded yield stress, is also discussed.
基金Projects(40272108,41402208)supported by the National Natural Science Foundation of ChinaProjects(ZR2012DL05,ZR2015EL044)supported by Shandong Provincial Natural Science Foundation,China+1 种基金Project(4072-114017)supported by Young Teachers’ Development of Shandong University of Technology,ChinaProject(J12LC51)supported by Shandong Province Higher Educational Science and Technology Program,China
文摘The effects of soil texture, initial water content and bulk density on diesel oil infiltration in fine sand and silty clay loam materials were evaluated. Three physical and two empirical equations express diesel oil infiltration through soils with time, with coefficients of determination greater than 0.99. Diesel oil infiltrates more quickly in the fine sand than in the silty clay loam material. Diesel oil infiltration rates are found to decrease with increasing initial water content and bulk density for the silty clay loam material. The infiltration rate of diesel oil in the fine sand material increases slightly with increasing initial water content. The diesel oil saturated conductivity(Kdiesel) decreases with increasing bulk density for the silty clay loam column. Diesel oil sorptivity(S) decreases linearly with increased initial water content and bulk density of the silty clay loam material. Changes in empirical parameters relative to initial water content and bulk density are similar to the parameter S.
基金supported by the Key Programs of Ministry of Education of China(Grant No.109046)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Eduation Ministrythe Program of Innovative Research Team of Education of China(Grant No.IRT0518)
文摘The capillary absorption of water by unsaturated cement-based material is the main reason of degradation of the structures subjected to an aggressive environment since water often acts as the transporting medium for damaging contaminants. It is well known that the capillarity coefficient and sorptivity are two important parameters to characterize the water absorption of porous materials. Generally, the former is used to describe the penetration depth or height of water transport, which must be measured by special and advanced equipment. In contrast, the sorptivity represents the relationship between cumulative volume of water uptake and the squareroot of the elapsed time, which can be easily measured by the gravimetric method in a normal laboratory condition. In the present study, an analytical method is developed to build up a bridge between these two parameters, with the purpose that the sorptivity or the gravimetric method can be used to predict the penetration depth of water absorption. Additionally, a new model to explain the dependence of sorptivity on initial water content of the material is developed in order to fit the in situ condition. The comparison of predicted results by the analytical method with experimental data or numerical calculation results, as well as some previous models, validates the feasibility of the methods presented in this paper.
基金the financial support of the National Natural Science Foundation of China(Grant Nos 51838001,51878070,51578079,51678074,51908069 and 51908073)the Special Funds for the Construction of Innovative Provinces in Hunan,China(Grant No.2019SK2171)+1 种基金Changsha Outstanding Innovative Youth Training Program(Grant No.kq1905043)the Double First-Class Scientific Research International Cooperation Expansion Project at Changsha University of Science&Technology(Grant No.2019IC04).
文摘The soil-water characteristic curve(SWCC)is often used to estimate unsaturated soil properties(e.g.strength,permeability,volume change,solute and thermal diffusivity).The SWCC of soil samples is significantly affected by cyclic wetting-drying.To examine how water content and cyclic wetting-drying affect the SWCC of disintegrated carbonaceous mudstone(DCM),SWCC tests were implemented using a pressure-plate apparatus.In addition,SWCC models for DCM considering the initial gravimetric water content and cyclic wetting-drying were developed.The test results showed that the volumetric water content(θ)of the DCM first decreased rapidly and then became stable as matric suction(s)increased.The initial water content affected the SWCC by altering the pore structure of the DCM.For a given number of wetting-drying cycles,the higher the initial water content,the higher the stabilizedθ.At a given s value,θdecreased as the number of wetting-drying cycles increased,which suggests that cyclic wetting-drying reduces the water-holding capacity of DCM.The Gardner model for DCM was constructed considering initial water content and cyclic wetting-drying,and was effective at describing and predicting the SWCC model for DCM.
基金This research project was financially supported by the Ministry of Science and Technology, Japan(Domestic Research Fellowship, 1999-2001)
文摘The compression behavior responsible for unity sensitivity is very valuable in quantitative assessment of the effects of soil structure on the compression behavior of soft marine sediments. However, the quantitative assessment of such effects is not possible because of unavailability of the formula for the compression curve of marine sediments responsible for unit sensitivity. In this study, the relationship between the remolded state and the conventional critical state line is presented in the deviator stress versus mean effective stress plot. The analysis indicates that the remolded state is on the conventional critical state line obtained at a relatively small strain. Thus, a unique critical state sedimentation line for marine sediments of unit sensitivity is proposed. The comparison between the critical state sedimentation line proposed in this study and the existing normalized consolidation curves obtained from conventional oedometer tests on remolded soils or reconstituted soils explains well the
基金National Natural Science Foundation of China (41571222)。
文摘To examine the working principle of vertical tube irrigation, variations in vertical tube emitter discharge and their causes were analyzed in the laboratory experiment. The effects of the pressure head, initial soil water content, and tube diameter on the emitter discharge of the vertical tube were studied. The results show that quantitative relationship between the time and cumulative infiltration and emitter discharge of the vertical tube is obtained, and R 2 is more than 0.98. Emitter discharge exhibits a positive and negative correlation with the pressure head and soil water content, respectively. Tube dia- meter has a nonsignificant effect on the emitter discharge. Changes of the soil water content around the emitter water outlet are the main causes of emitter discharge variations. In the experiments, the range of vertical tube emitter discharge is 0.056-1.102 L/h. The emitter of vertical tube irrigation automatically adjusts the soil water content and maintains the root zone soil water content within an appropriate range, which achieves continuous irrigation, and further achieves the effect of water-saving.
基金supported by Changjiang Scholars and Innovative Research Team in University of China(IRT13039)Special Fund for Agro-scientific Research in the Public Interest(201503136)
文摘Mulching and soil water content(SWC) have a significant impact on soil erosion,and this study investigated the effect of straw mulching on water infiltration and soil loss under different initial SWC treatments in a rainfall simulation experiment conducted in northern China.Increasing initial SWC can decrease soil infiltration and increase soil loss.During an 80 mm rainfall event(80 mm·h–1for 60 min),8%,12% and 16% initial SWC treatments decreased cumulative infiltration by8.7%,42.5% and 58.1%,and increased total sediment yield by 44,146 and 315 g,respectively,compared to 4%initial SWC.However,in all the straw mulching treatments,there was no significant difference in stable infiltration rate between the different initial SWC treatments.For all initial SWC treatments,straw mulching of30% or more significantly enhanced water infiltration by over 31% and reduced soil loss by over 49%,compared to the unmulched treatment.Taking into consideration the performance of no-till planters,a maize straw mulching rate of 30% to 60%(1400–3100 kg·hm–2) is recommended for the conservation of water and soil in northern China.