圆形基坑极正交各向异性支护结构变形解析分析

Analytical Analysis of Deformation of Polar Orthotropic Supporting Structure of Circular Foundation Pit

考虑圆形深基坑支护结构轴向和环向配筋的差异,将支护结构简化为极正交各向异性圆柱薄壳,研究了分层土体中具有弹性支撑环梁约束的支护结构轴对称变形和内力特征.首先,将弹性支撑环梁的约束解除,代之以沿环向分布的未知集中力,基于弹性环梁和圆柱壳的边界条件和变形协调条件,得到了分层土体中具有弹性支撑环梁支护结构轴对称变形的解析解.其次,以上海地区某一圆形深基坑支护结构为例,揭示了支护结构环向和纵向弹性模量、环梁刚度、土体重度和静止土压力系数等因素对支护结构内力和变形的影响,结果表明:支护结构以环向承压为主,轴向弯曲为辅,故其环向刚度对径向位移的影响要明显大于其轴向刚度的影响,但材料参数对内力分布影响较弱;环梁刚度的增加可有效限制支护结构的变形,但会引起支护结构在支撑环梁处内力的显著增大;土层性质相差不大区域的支护结构可按均质土中支护结构进行分析,而土层性质有较大突变区域的支护结构分析则需考虑土层的分层效应.

Considering the difference between the axial and circumferential reinforcements of the supporting structure of circular deep foundation pit,the supporting structure is simplified as a polar orthotropic cylindrical thin shell,and axisymmetric deformation and internal force characteristics of the supporting structure with elastic ring beam in layered soil are analyzed.First,the constraint of the elastic ring beam on the supporting structure is removed and replaced with the unknown concentrated force distributed along the circumferential direction.Based on the boundary conditions and deformation compatibility conditions between elastic ring beam and cylindrical shell,the axisymmetric analytical solution of the supporting structure with elastic ring beam in layered soils is obtained.Then,taking the supporting structure of a circular deep foundation pit in Shanghai as an example,the influences of axial and circumferential elastic modulus,stiffness of ring beam,soil gravity and static earth pressure coefficient on the internal forces and deformation of supporting structure are revealed.It is shown that the supporting structure is dominated by the circumferential pressure force and supplemented by the axial bending moment,so the influence of circumferential stiffness on the radial displacement is obviously greater than that of axial stiffness,but the influence of material parameters on internal force is weaker.The increase of ring beam stiffness can effectively limit the deformation of the supporting structure,but the internal forces of the supporting structure at the ring beams will increase significantly.The supporting structure in areas with little difference in soil layer properties can be analyzed as the supporting structure in homogeneous soil,while the supporting structure in areas with abrupt changes in soil layer properties needs to be analyzed considering the stratification effect of soil.