Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was de...Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was derived by Laplace transformation method.The responses in time domain were obtained by inverse Fourier transformation.The results of the analytical solution proposed agree well with the solutions in homogenous soil.The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched.The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil.The smaller the shear modulus,the larger the amplitude of velocity admittance.The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil.The displacements of the piles with the same damping coefficients of the outer soil have less difference.Moreover,the effects of the distribution of soil layers are analyzed.The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer.A larger damping coefficient of the upper layer results in a smaller velocity admittance.The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.展开更多
Sustainable agricultural production is of vital importance to food supply security. This study aimed to investigate crop yield response to spatial variability of soil quality at a county scale in the North China Plain...Sustainable agricultural production is of vital importance to food supply security. This study aimed to investigate crop yield response to spatial variability of soil quality at a county scale in the North China Plain （NCP） and subsequently derive key soil quality indicators. Soil samples were geo-referenced and taken in 2008 from both surface （0-20 cm） and subsurface （20-40 cm） layers in 132 fields throughout the Fengqiu County, located in the centre of the NCP, for subsequent soil properties＇ analyses. Annum crop yields were obtained from the same fields where soil samples were collected. Soil quality was evaluated based on a fuzzy set with 13 soil properties, and its spatial distributions were investigated by integrating geostatistical analysis and geographic information system （GIS） techniques. Soil quality indices were classified into five grades, and their spatial distributions were mapped within the county. The surface soil qualities were about one to two grades higher than the subsurface soil. The quality indices for surface and subsurface soils were positively associated with the annual crop yields, suggesting the importance of both. Soil organic matter, total nitrogen, available P, and available K contributed 50% of the combined weight to the soil quality index and were identified as key indicators of soil quality status in the area in terms of sustainability.展开更多
基金Project(U1134207)supported by the National Natural Science and High Speed Railway Jointed Foundation of ChinaProject(B13024)supported by the "111" Program of China+1 种基金Project(BK2012811)supported by the Nature Science Foundation of Jiangsu Province,ChinaProject(NCET-12-0843)supported by the Fund for New Century Excellent Talents in Universities,China
文摘Considering the viscous damping of the soil and soil-pile vertical coupled vibration,a computational model of large-diameter pipe pile in layered soil was established.The analytical solution in frequency domain was derived by Laplace transformation method.The responses in time domain were obtained by inverse Fourier transformation.The results of the analytical solution proposed agree well with the solutions in homogenous soil.The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched.The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil.The smaller the shear modulus,the larger the amplitude of velocity admittance.The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil.The displacements of the piles with the same damping coefficients of the outer soil have less difference.Moreover,the effects of the distribution of soil layers are analyzed.The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer.A larger damping coefficient of the upper layer results in a smaller velocity admittance.The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.
基金supported by the National Basic Research Program of China (No. 2011CB100506)the National Natural Science Foundation of China (No. 41271311)+1 种基金the National Key Technology Support Program of China (No. 2012BAD05B0203)the Knowledge Innovation Program of Chinese Academy of Sciences (No. ISSASIP1118)
文摘Sustainable agricultural production is of vital importance to food supply security. This study aimed to investigate crop yield response to spatial variability of soil quality at a county scale in the North China Plain （NCP） and subsequently derive key soil quality indicators. Soil samples were geo-referenced and taken in 2008 from both surface （0-20 cm） and subsurface （20-40 cm） layers in 132 fields throughout the Fengqiu County, located in the centre of the NCP, for subsequent soil properties＇ analyses. Annum crop yields were obtained from the same fields where soil samples were collected. Soil quality was evaluated based on a fuzzy set with 13 soil properties, and its spatial distributions were investigated by integrating geostatistical analysis and geographic information system （GIS） techniques. Soil quality indices were classified into five grades, and their spatial distributions were mapped within the county. The surface soil qualities were about one to two grades higher than the subsurface soil. The quality indices for surface and subsurface soils were positively associated with the annual crop yields, suggesting the importance of both. Soil organic matter, total nitrogen, available P, and available K contributed 50% of the combined weight to the soil quality index and were identified as key indicators of soil quality status in the area in terms of sustainability.
