超长L形深基坑台阶法开挖围护结构变形特征研究

Research on the Deformation Characteristics of Enclosure Structure of Super-long L-shaped Deep Foundation Pit Excavated by Bench Method

通过对南宁地铁那洪立交站基坑工程的施工监测,分析了不同施工阶段地下连续墙围护结构的墙顶竖向位移、墙顶水平位移和墙体深层水平位移的变化规律,研究了超长L形深基坑台阶法开挖围护结构的变形特征。研究结果表明:L形基坑围护结构变形的形状效应显著,长边段中部的墙顶竖向位移量最大,交汇处次之,短边端最小;开挖深度较浅时,墙顶竖向位移以沉降为主,随着深度增加,围护结构发生波动隆起变形;同一区段内墙顶水平位移方向相一致,以向坑内变形为主;坑内开挖深度差导致不同深度侧的墙顶水平变形量差异较大,且变形方向相反。此外,还得到了不同开挖深度对应的墙体深层水平位移最大值变化范围及其所处深度范围。

Based on the field monitoring of the foundation pit project of Nahong Overpass Station of Nanning Metro,the laws of vertical displacement of wall top,horizontal displacement of wall top and deep horizontal displacement of wall body at different construction stages of the underground diaphragm wall enclosure structure are analyzed.The deformation characteristics of the enclosure structure of the super-long L-shaped deep foundation pit excavated by bench method is studied.The results show that the shape effect of deformation is significant to the L-shaped foundation pit enclosure structure.The vertical displacement of wall top in the middle of the long side section is the biggest,the intersection the second,and the short side the smallest.When the depth of excavation is shallow,the vertical displacement of wall top is dominated by settlement.As the depth increases,the enclosure structure undergoes waveform uplift deformation.The horizontal displacement direction of wall top is consistent in the same section,and the deformation direction mainly heads towards inside the foundation pit.Large differences appear in the horizontal deformation of wall top on different depth sides,which is created by the various excavation depths inside the pit,and the deformation direction is opposite.In addition,the variation range of the maximum deep horizontal displacement of wall body and its depth range corresponding to different excavation depths are also obtained.