A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil pe...A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil permeability. In order to confirm the acceptability of the one-dimensional horizontal infiltration method（one-D method） for simultaneously determining both the saturated and unsaturated permeability coefficients of loamy sand, we first measured the cumulative infiltration and the wetting front distance under various infiltration heads through a series of one-dimensional horizontal infiltration experiments, and then analyzed the relationships of the cumulative horizontal infiltration with the wetting front distance and the square root of infiltration time. We finally compared the permeability results from Gardner model based on the one-D method with the results from other two commonly-used methods（i.e., constant head method and van Genuchten model） to evaluate the acceptability and applicability of the one-D method. The results showed that there was a robust linear relationship between the cumulative horizontal infiltration and the wetting front distance, suggesting that it is more appropriate to take the soil moisture content after infiltration in the entire wetted zone as the average soil moisture content than as the saturated soil moisture content. The results also showed that there was a robust linear relationship between the cumulative horizontal infiltration and the square root of infiltration time, suggesting that the Philip infiltration formula can better reflect the characteristics of cumulative horizontal infiltration under different infiltration heads. The following two facts indicate that it is feasible to use the one-D method for simultaneously determining the saturated and unsaturated permeability coefficients of loamy sand. First, the saturated permeability coefficient（prescribed in the Gardner model） of loamy sand obtained from the one-D method well agreed with the value obtained from the constant head method. Second, the relationship of unsaturated permeability coefficient with soil water suction for loamy sand calculated using Gardner model based on the one-D method was nearly identical with the same relationship calculated using van Genuchten model.展开更多
To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse...To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse were investigated. The permeability tests were carried using unidirectional and biaxial noncrimp carbon fabric( NCF) by linear capacitance sensors and ultrasound monitor system. The results indicate that the internal flow behavior and permeability in plane with different stitch and overlay placement styles are significantly different. When flow channels formed by stitches penetrate along the fiber direction,the permeability is high in one direction, which makes the in-plane principle permeabilities K_1 and K_2 significantly different. When there is an angle between the flow channel and fiber direction,the in-plane principle permeabilities on all directions are nearly the same and the flow process is close to isotropy. As to transverse permeability,the exist of flow channels on thickness influences it greatly and it is about 1-2 orders of magnitude lower in unidirectional fabric than that in biaxial NCF.展开更多
基金funded by the National Basic Research Program of China (2013CB429902)the National Natural Science Foundation of China (U1303181, 41671032)
文摘A knowledge of soil permeability is essential to evaluate hydrologic characteristics of soil, such as water storage and water movement, and soil permeability coefficient is an important parameter that reflects soil permeability. In order to confirm the acceptability of the one-dimensional horizontal infiltration method（one-D method） for simultaneously determining both the saturated and unsaturated permeability coefficients of loamy sand, we first measured the cumulative infiltration and the wetting front distance under various infiltration heads through a series of one-dimensional horizontal infiltration experiments, and then analyzed the relationships of the cumulative horizontal infiltration with the wetting front distance and the square root of infiltration time. We finally compared the permeability results from Gardner model based on the one-D method with the results from other two commonly-used methods（i.e., constant head method and van Genuchten model） to evaluate the acceptability and applicability of the one-D method. The results showed that there was a robust linear relationship between the cumulative horizontal infiltration and the wetting front distance, suggesting that it is more appropriate to take the soil moisture content after infiltration in the entire wetted zone as the average soil moisture content than as the saturated soil moisture content. The results also showed that there was a robust linear relationship between the cumulative horizontal infiltration and the square root of infiltration time, suggesting that the Philip infiltration formula can better reflect the characteristics of cumulative horizontal infiltration under different infiltration heads. The following two facts indicate that it is feasible to use the one-D method for simultaneously determining the saturated and unsaturated permeability coefficients of loamy sand. First, the saturated permeability coefficient（prescribed in the Gardner model） of loamy sand obtained from the one-D method well agreed with the value obtained from the constant head method. Second, the relationship of unsaturated permeability coefficient with soil water suction for loamy sand calculated using Gardner model based on the one-D method was nearly identical with the same relationship calculated using van Genuchten model.
基金National Natural Science Foundation of China(No.11472077)Shanghai Natural Science Foundation,China(No.13ZR1400500)+1 种基金the Fundamental Research Funds for the Central Universities,China(No.2232015D3-01)Innovation Experiment Programs for University Students,China(Nos.201410255024,201510255118)
文摘To study the resin flow and the permeability in fabric preforms during the liquid composite molding( LCM) process,influences of stitch and overlay placement styles on the internal flow behavior in-plane and transverse were investigated. The permeability tests were carried using unidirectional and biaxial noncrimp carbon fabric( NCF) by linear capacitance sensors and ultrasound monitor system. The results indicate that the internal flow behavior and permeability in plane with different stitch and overlay placement styles are significantly different. When flow channels formed by stitches penetrate along the fiber direction,the permeability is high in one direction, which makes the in-plane principle permeabilities K_1 and K_2 significantly different. When there is an angle between the flow channel and fiber direction,the in-plane principle permeabilities on all directions are nearly the same and the flow process is close to isotropy. As to transverse permeability,the exist of flow channels on thickness influences it greatly and it is about 1-2 orders of magnitude lower in unidirectional fabric than that in biaxial NCF.
