片式冠梁双排桩支护结构的变形受力特性研究

RESEARCH ON PROPERTIES OF DEFORMATION AND MECHANICS ON DOUBLE-ROW PILE STRUCTURE WITH FLAKE TOP BEAM

采用MIDAS-GTS软件,建立起同时考虑土层、实体支护结构、桩土界面Goodman单元以及实际施工过程的片式冠梁双排桩支护基坑三维有限元分析模型。分析表明:片式冠梁在基坑规模不大时对支护桩水平位移具有较强的约束作用,且冠梁的最大弯矩及剪力位于坑角附近。在其他参数不变、仅冠梁长度改变的情况下,冠梁的水平位移曲线、冠梁剪力曲线可视为自变量是坑角水平距离值的一元函数,与冠梁本身的长度关系不大。当冠梁高度增大时,冠梁的弯矩及剪力值均明显增加,但冠梁水平位移减少并不明显。而冠梁参数不变时,随着基坑开挖深度的增加,基坑长侧中部处冠梁的水平位移、弯矩及剪力有加速增大至失稳破坏的趋势。随着排距的增大,长边冠梁的水平位移、弯矩及剪力的最大值会逐渐减少,但减少的速率也在降低。桩距的增大对长边冠梁的位移及受力情况影响较小。

The 3D FEM software MIDAS-GTS was used for establishing numerical analysis model of double-row pile structure with flake top beam, in which practical soil layers, solid supporting structures, Goodman contact elements and actual construction stages were simulatneously considered. The resulted of the study showed that the horizontal displacement of supporting pile was strongly limited by flake top beam when the size of deep excavation was not large enough. The maximum values of bending moment and shearing force of top beam always appeared near the corner of the excavation. Along with change of the length of top beam, while other parameters were fixed, the curves of horizontal displacement and shear force of top beam were just single variable function with only one argument （horizontal displacement from the corner of the excavation） ,which little related with the length of top beam. When the hight of top beam was raised, the bending moment and shearing force of top beam were highly increased but the decrease of horizontal displacement of top beam was not sharp. Along with increasing of the depth of the excavation, the value of bending moment and internal force in the middle of top beam rose obviously. While the distance between the front and back pile increased, the value of bending moment and internal force in the middle of top beam decreased, yet, the rate of reduction also decreased. The increment of the distance between the front and back pile impacted the bending moment and internal force of top beam slightly.