基坑开挖对超深软土复合地基桩体的影响研究

Study on Influence of Foundation Pit Excavation on Pile in Composite Foundation in Super Soft and Deep Soft Soil Area

复合地基中素混凝土桩是一种易脆性折断的桩体。为研究场地真空预压及基坑开挖作用下超软超深软土区域桩体的受力特征,本文采用数值计算分析了真空预压及基坑开挖作用下素混凝土桩的轴力、弯矩和剪力变化规律。结果表明:越靠近基坑开挖侧,桩体位移越大,近基坑侧桩身上部至下部轴力逐渐减小,而弯矩主要分布在群桩的两侧并随开挖的进行逐渐增大;轴力和弯矩最大值出现在桩身1/3处,分别达到了85kN和13.5kN·m/m,剪力最大值处在开挖面标高位置为5.5kN/m,桩体的承载能力验算表明受拉侧会出现断裂。最后基于超软超深软土区域素混凝土桩的成桩特点,提出了防止桩体断裂的施工措施。

Plain concrete pile is a kind of pile prone to brittle fracture.In order to study the Variation law of pile force in super and deep soft soil under vacuum preloading and foundation pit excavation,the axial force,bending moment and shear force of plain concrete pile under vacuum preloading and foundation pit excavation are analyzed by numerical caculation.The results show that the lateral pile displacement increases as the pile is closer to the foundation pit excavation,and the axial force from the pile body to the lower part of the foundation pit decreases gradually,while the bending moment is mainly distributed on both sides of the pile group and increases with the progress of excavation.The maximum axial force and bending moment appear at 1/3 of the pile body,reaching 85kN and 13.5kN·m/m respectively.The maximum shear force at the elevation of excavation face is 5.5kN/m.The checking calculation of the bearing capacity of the pile shows that the tensile side will be broken.Finally,based on the forming characteristics of plain concrete pile in super and deep soft soil area,the construction measures to prevent pile breakage are put forward.