A simple semi-empirical analysis method for predicting the group effect of pile group under dragload embedded in clay was described assuming an effective influence area around various locations of pile group. Various ...A simple semi-empirical analysis method for predicting the group effect of pile group under dragload embedded in clay was described assuming an effective influence area around various locations of pile group. Various pile and soil parameters such as the array of pile group, spacing of the piles (S), embedment length to diameter ratio of piles (L/D) and the soil properties such as density (γ), angle of internal friction (φ) and pile-soil interface friction coefficient (μ) were considered in the analysis. Model test for dragload of pile group on viscosity soil layer under surface load consolidation conditions was studied. The variations of dragload of pile, resistance of pile tip and the layered settlement of soil with consolidation time were measured. In order to perform comparative analysis, single pile was tested in the same conditions. The predicted group effect values of pile group under dragload were then compared with model test results carried out as a part of the present investigation and also with the values reported in literatures. The predicted values were found to be in good agreement with the measured values, validating the developed analysis method. The model test results show that negative skin friction of pile shaft will reach 80%-90% of its maximum value, when pile-soil relative displacement reaches 2 mm.展开更多
This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of bot...This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of both a single pile and pile groups.Considering the pile group effect and the skin friction from both outer and inner soils,an analytical solution is developed to calculate the settlement and axial force in large-diameter pipe pile groups.The analytical solution was verified by centrifuge and field testing results.An extensive parametric analysis was performed to study the bearing performance of the pipe pile groups.The results reveal that the axial forces in group piles are not the same.The larger the distance from central pile,the larger the axial force.The axial force in the central pile is the smallest,while that in corner piles is the largest.The axial force on the top of the corner piles decreases while that in the central pile increases with increasing of pile spacing and decreasing of pile length.The axial force in side piles varies little with the variations of pile spacing,pile length,and shear modulus of the soil and is approximately equal to the average load shared by one pile.For a pile group,the larger the pile length is,the larger the influence radius is.As a result,the pile group effect is more apparent for a larger pile length.The settlement of pile groups decreases with increasing of the pile number in the group and the shear modulus of the underlying soil.展开更多
This study presents a numerical simulation of large-scale shaking table tests on a superstructure supported by a pile group installed in an inclined liquefiable site,fo-cusing on nonlinear interactions between piles a...This study presents a numerical simulation of large-scale shaking table tests on a superstructure supported by a pile group installed in an inclined liquefiable site,fo-cusing on nonlinear interactions between piles and the soil.A three-dimensional finite element model of a soil-pile superstructure system is developed using OpenSeesMP.The temporal and spatial evolution of the radial soil pressure around the pile is evaluated in both liquefied and nonlique-fied sites.Results show that the soil pressure around the pile is significantly influenced by site inclination and soil lateral spreading.In liquefied sites,the soil pressure in the ex-truded zone of the upstream pile is significantly higher than that in the diffused zone.However,higher pressure occurs in the diffused zone for nonliquefied sites.Correspond-ingly,the liquefaction state significantly influences the force characteristics of the pile group system.Additionally,the group effect is more pronounced in liquefied sites.The results also indicate that the soil pressure distribution around the piles is closely related to the relative pile-soil displace-ment and reveals different on-pile force mechanisms under varying site conditions.These findings offer valuable in-sights into the seismic design of pile foundations in inclined liquefied sites.展开更多
基金Project(50679015) supported by the National Natural Science Foundation of China
文摘A simple semi-empirical analysis method for predicting the group effect of pile group under dragload embedded in clay was described assuming an effective influence area around various locations of pile group. Various pile and soil parameters such as the array of pile group, spacing of the piles (S), embedment length to diameter ratio of piles (L/D) and the soil properties such as density (γ), angle of internal friction (φ) and pile-soil interface friction coefficient (μ) were considered in the analysis. Model test for dragload of pile group on viscosity soil layer under surface load consolidation conditions was studied. The variations of dragload of pile, resistance of pile tip and the layered settlement of soil with consolidation time were measured. In order to perform comparative analysis, single pile was tested in the same conditions. The predicted group effect values of pile group under dragload were then compared with model test results carried out as a part of the present investigation and also with the values reported in literatures. The predicted values were found to be in good agreement with the measured values, validating the developed analysis method. The model test results show that negative skin friction of pile shaft will reach 80%-90% of its maximum value, when pile-soil relative displacement reaches 2 mm.
基金supported by the Joint High Speed Railway Key Program of National Natural Science Foundation of China (Grant No.U1134207)the National Natural Science Foundation of China (Grant No.51378177)+1 种基金the Program for Excellent University Talents in New Century (Grant No.NCET-12-0843)the Fundamental Research Fund for the Central Universities (Grant No.106112014CDJZR200007)
文摘This paper aims to present a theoretical method to study the bearing performance of vertically loaded large-diameter pipe pile groups.The interactions between group piles result in different bearing performance of both a single pile and pile groups.Considering the pile group effect and the skin friction from both outer and inner soils,an analytical solution is developed to calculate the settlement and axial force in large-diameter pipe pile groups.The analytical solution was verified by centrifuge and field testing results.An extensive parametric analysis was performed to study the bearing performance of the pipe pile groups.The results reveal that the axial forces in group piles are not the same.The larger the distance from central pile,the larger the axial force.The axial force in the central pile is the smallest,while that in corner piles is the largest.The axial force on the top of the corner piles decreases while that in the central pile increases with increasing of pile spacing and decreasing of pile length.The axial force in side piles varies little with the variations of pile spacing,pile length,and shear modulus of the soil and is approximately equal to the average load shared by one pile.For a pile group,the larger the pile length is,the larger the influence radius is.As a result,the pile group effect is more apparent for a larger pile length.The settlement of pile groups decreases with increasing of the pile number in the group and the shear modulus of the underlying soil.
基金The National Science Fund for Distinguished Young Scholars (No. 52225807)。
文摘This study presents a numerical simulation of large-scale shaking table tests on a superstructure supported by a pile group installed in an inclined liquefiable site,fo-cusing on nonlinear interactions between piles and the soil.A three-dimensional finite element model of a soil-pile superstructure system is developed using OpenSeesMP.The temporal and spatial evolution of the radial soil pressure around the pile is evaluated in both liquefied and nonlique-fied sites.Results show that the soil pressure around the pile is significantly influenced by site inclination and soil lateral spreading.In liquefied sites,the soil pressure in the ex-truded zone of the upstream pile is significantly higher than that in the diffused zone.However,higher pressure occurs in the diffused zone for nonliquefied sites.Correspond-ingly,the liquefaction state significantly influences the force characteristics of the pile group system.Additionally,the group effect is more pronounced in liquefied sites.The results also indicate that the soil pressure distribution around the piles is closely related to the relative pile-soil displace-ment and reveals different on-pile force mechanisms under varying site conditions.These findings offer valuable in-sights into the seismic design of pile foundations in inclined liquefied sites.
