砂层锁扣钢管桩围堰受力变形规律分析

Analysis on Stress and Deformation Rules of Locking Steel Pipe Pile Cofferdam in Deep Foundation Excavation with Sand Layer

西安地铁10号线深基坑处于西北地区特殊的富水砂层中,渗透性强、土体黏聚力低、自稳性差,为确保此地质下深基坑施工过程中锁扣钢管桩围堰结构安全,通过三维数值模拟和现场监测方法,研究由基坑开挖引起的锁扣钢管桩围堰桩身水平位移、内支撑轴力及周边地表沉降规律。深基坑施工过程中,锁扣钢管桩围堰强度、刚度及稳定性均满足规范要求,有限元计算值与实测桩身位移分布规律基本相同。随着基坑开挖深度增大,桩体侧斜曲线呈两端变形小、中间变形大的鼓肚状,钢围堰第1层内支撑轴力呈先增大后减小趋势,地表沉降累计变化时程曲线为沉降型,基坑邻河侧的桩身变形和地表沉降均大于基坑背河侧。

The deep foundation excavation of Xi’an Metro Line 10 locates in the special water-rich sand layer in northwest China,the sand layer has the characteristics of strong permeability,low cohesiveness and poor self-stability,in order to ensure the safety of locked steel pipe pile cofferdam structure during the construction for geological deep foundation excavation,through 3D numerical simulation and field monitoring methods,the horizontal displacement,axial force of inner support and surrounding surface settlement of latched-steel pipe pile cofferdam caused by foundation excavation are studied.The strength,stiffness and stability of locking steel pipe pile cofferdam during construction of deep foundation excavation all meet the specification requirements,and the finite element calculation value is basically the same as the measured pile displacement distribution law,with the excavation of the foundation excavation.As the depth deepens,the side slope curve of the pile body takes on a bulging shape with small deformation at both ends and large deformation in the middle.The support axial force in the first layer of the steel cofferdam shows a trend of first increasing and then decreasing,the cumulative change time history curve of surface settlement is a settlement type,the pile deformation and surface settlement on the side of foundation excavation facing the river are larger than those on the side of the foundation excavation away from the river.