Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but...Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.展开更多
As a new kind of technology in retaining structures, the characteristics of double-row piles are significantly affected by spatial effects. In this paper, double-row piles as a retaining structure are simulated numeri...As a new kind of technology in retaining structures, the characteristics of double-row piles are significantly affected by spatial effects. In this paper, double-row piles as a retaining structure are simulated numerically in three-dimension by finite element software PLAXIS 3D FOUNDATION. The behavior differences of piles in different positions around the foundation pit are analyzed. By changing the parameters, including the length-width ratio, the excavation depth, the distance between rows and the diameter of piles, the variations of the lateral deformation, the bending moment and the earth pressure around the piles are determined. The reasonable values of parameters and some suggestions with consideration of earth pressure are proposed for the design of double-row piles as a retaining structure. The results show that the lateral deformation and bending moment are the largest in the middle of long side of the foundation pit, which is identified as the most unfavorable position. It is indicated that the earth pressure between rows above pit bottom is close to active earth pressure, while the earth pressure between rows under pit bottom is close to static earth pressure. It is suggested that 1/2-2/3 of pile length, 0.6-1.2 m, 3d-6d, and 2d-2.5d be chosen as embedded depth of piles, diameter of piles, distance between rows, and distance between piles, respectively, where d is the pile diameter.展开更多
This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upo...This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upon excavation.The horizontal displacement(δ_(h)),Von Mises stress(δ_(M)),strain(ε),ground surface settlement(δ_(v)),and earth pressure are systematically investigated.Furthermore,the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and discussed.The experimental results can basically match the numerical results,and the maximumδ_(M),maximum bending moment(M_(max)),maximum horizontal displacement(δ_(hm))of structural members are all less than the tolerance limits.The ground surface settlement model of double-row piles retaining system consists of three zones,i.e.,rebound influence zone,primary influence zone and secondary influence zone.The dhm values are 0.07%–1.42%of the excavation depth(He).The maximum ground surface settlement(δ_(vm))is generally less than dhm.The ratio ofδ_(vm)=δ_(hm)varies between 0.09 and 0.76,with an average value of 0.5.The observed earth pressure on the retained side of front pile(paf)is about 0.53–0.57γH below the excavation surface.Above the excavation surface,p_(af)decreases dramatically when getting closer to the ground surface.展开更多
基金the Key Research Program of Shanghai Construction Group(No.17JCSF-37)。
文摘Double-row pile(DRP)retaining systems have been widely used in deep excavations in China.Soil between the front and back-row piles(FBP soil)is often improved to decrease the displacement of DRPs in soft soil areas,but the improvement efficiency has rarely been researched.A large and deep excavation supported by a DRP retaining system is introduced,and the effect of FBP soil improvement is discussed by comparing the finite element analysis and the monitoring results.Then,a parametric study of DRP using the finite element method considering the small strain of soil is conducted to investigate the effect of FBP soil improvement.It was shown that the pile deflection and bending moment decrease when the FBP soil is improved.Moreover,the most efficient way to minimize the pile deflection and bending moment is to improve the FBP soil around the excavation level.The FBP soil improvement 2-4 m below the pile head is not very useful for reducing the pile deflection and can be eliminated when the pile displacement limit is not very strict.
文摘As a new kind of technology in retaining structures, the characteristics of double-row piles are significantly affected by spatial effects. In this paper, double-row piles as a retaining structure are simulated numerically in three-dimension by finite element software PLAXIS 3D FOUNDATION. The behavior differences of piles in different positions around the foundation pit are analyzed. By changing the parameters, including the length-width ratio, the excavation depth, the distance between rows and the diameter of piles, the variations of the lateral deformation, the bending moment and the earth pressure around the piles are determined. The reasonable values of parameters and some suggestions with consideration of earth pressure are proposed for the design of double-row piles as a retaining structure. The results show that the lateral deformation and bending moment are the largest in the middle of long side of the foundation pit, which is identified as the most unfavorable position. It is indicated that the earth pressure between rows above pit bottom is close to active earth pressure, while the earth pressure between rows under pit bottom is close to static earth pressure. It is suggested that 1/2-2/3 of pile length, 0.6-1.2 m, 3d-6d, and 2d-2.5d be chosen as embedded depth of piles, diameter of piles, distance between rows, and distance between piles, respectively, where d is the pile diameter.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFC3100803)the National Natural Science Founda tion of China(Grant Nos.52208380 and 52078506)+2 种基金the Guangdong Basic and Applied Basic ResearchFoundation,China(Grant No.2023A1515012159)Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences(Grant No.SKLGME021022)the Science and Technology Program of Guangzhou Municipal Construction Group Co.,Ltd.,China(Grant No.2022-KJ004).
文摘This paper introduces a new prefabricated recyclable double-row piles retaining system for excavations in silty clay ground.Laboratory model test and numerical simulation are conducted to study the system behavior upon excavation.The horizontal displacement(δ_(h)),Von Mises stress(δ_(M)),strain(ε),ground surface settlement(δ_(v)),and earth pressure are systematically investigated.Furthermore,the monitoring data of 13 excavation cases supported by double-row piles retaining system are presented and discussed.The experimental results can basically match the numerical results,and the maximumδ_(M),maximum bending moment(M_(max)),maximum horizontal displacement(δ_(hm))of structural members are all less than the tolerance limits.The ground surface settlement model of double-row piles retaining system consists of three zones,i.e.,rebound influence zone,primary influence zone and secondary influence zone.The dhm values are 0.07%–1.42%of the excavation depth(He).The maximum ground surface settlement(δ_(vm))is generally less than dhm.The ratio ofδ_(vm)=δ_(hm)varies between 0.09 and 0.76,with an average value of 0.5.The observed earth pressure on the retained side of front pile(paf)is about 0.53–0.57γH below the excavation surface.Above the excavation surface,p_(af)decreases dramatically when getting closer to the ground surface.
