Model test and numerical simulation of a new prefabricated double-row piles retaining system in silty clay ground

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.

Three-dimensional numerical simulation and earth pressure analysis on double-row piles with consideration of spatial effects

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.

天津港7号、8号泊位改造工程原挡土结构安全性评估

天津港 7号、8号泊位将由件杂货码头改造为集装箱码头 ,改造后码头工艺荷载发生了变化 ,文中对码头改造后挡土结构在新工艺载作用下的安全性进行了评估 。

带墩双排桩在基坑开挖中的工作性状分析

对于平面面积较大的基坑,常规双排桩支护结构在基坑长边中部往往出现较大位移而可能导致失效,为改善其力学性能,本文提出一种带墩双排桩支护结构体系,并利用Midas GTS有限元软件建模分析佛山某工程实例基坑开挖中的工作性状,研究结果表明墩距及墩自身刚度的影响较大,墩距不宜大于60m,墩自身平面尺寸不宜小于8m×4m。