深基坑桩锚支护结构受力与变形特性现场试验

在成都地区某基坑支护工程开展了深基坑条件下桩锚支护结构受力与变形特性现场试验,研究了冠梁上土压力与内力变化规律、锚索轴力及支护桩侧向位移分布特征。结果表明:(1)在基坑中部,冠梁对桩顶侧向位移有一定的协调作用,角点处冠梁协调作用较弱,应适当提高冠梁刚度,并将其与其他部位断开;(2)锚索轴力沿基坑深度呈类抛物线型分布,且(0~2/3)倍基坑最终开挖深度he范围内的中上层锚索对支护桩顶侧向位移影响比较明显,施工时应尽量控制该深度范围的开挖速度及重点关注中上层锚索预应力损失;(3)受边界效应影响,基坑变形具有空间效应特征,具体表现为基坑中部大于角点处、长边大于较短边,边界效应对其影响范围大致为1h_e。

Filed Test of Pile-anchor Retaining Structure Mechanical and Deformation Characteristics in Deep Foundation Pit

A deep foundation pit filed test about pile-anchor retaining structure mechanical and deformation characteristics has carried out in Chengdu area,studied the earth pressure on top beam and internal force variation law,the distribution characteristics of anchor axial force and pile lateral displacement.The result showed:① in the middle of the foundation pit,the top beam has the coordinating role to the pile top lateral displacement,but the top beam play a weak coordinating role to the corner pile,so should be enhance top beam stiffness,and disconnect with the other parts;② anchor axial force along the foundation pit depth distribution is likely the parabolic type,and the upper-middle-class anchor cable which within the scope of (0～2/3) times of ultimate excavation depth(he),has an obvious effect to the pile top lateral displacement,so under construction,should be the control the excavation speed of this depth scope and the focus on upper-middle-class prestress loss;③ affected by the boundary effect,the lateral deformation of foundation pit has spatial effect,specific manifested as that:the lateral deformation of foundation central is greater than corner,the long side of foundation pit is greater than shorter side,and influence scope of boundary effect to lateral displacement is about 1he.