考虑椭圆度缺陷的盾构管片结构极限承载性能研究

为了探究初始椭圆度缺陷对于管片结构在外部围压下极限承载性能的影响，提出考虑初始椭圆度缺陷的管片非线性稳定极限承载性能计算方法.建立数值分析模型并基于文献实验数据验证，对椭圆度缺陷的几何计算理论及其取值进行分析；分别引入横长轴和斜长轴初始椭圆度缺陷，就不同椭圆度缺陷对管片非线性稳定极限承载力的影响进行参数分析；提出含椭圆度缺陷管片极限稳定承载力的取值建议.结果表明，初始椭圆度缺陷对管片非线性极限承载力均为不利作用，且缺陷越大，不利越明显.当不同椭圆度缺陷时，荷载系数随位移的变化均为迅速增大、平缓增大和趋于收敛.当不同横长轴椭圆度缺陷时，极限荷载系数的变化趋势为：以土体侧压力系数0.6为界，经历缓慢增大、迅速增大；以土体抗力系数5.0 MN/m3为界，经历迅速增大、缓慢增大；以接头抗弯刚度50.0 MN·m/rad为界，经历迅速增大、趋于平稳.对于不同椭圆度缺陷，随着倾斜角的增大，极限荷载系数逐渐增大，对应误差百分比绝对值逐渐减小，横长轴椭圆度缺陷为最不利工况.在实际工程中含椭圆度缺陷管片的非线性极限承载力相对无缺陷时的折减系数可按0.85～0.90考虑，而按整体式管片近似求解实际衬砌式管...

Ultimate bearing capacity of shield segment structures considering ovality imperfection

A calculation method of nonlinear stability ultimate bearing capacity for shield segments considering the initial ovality imperfection was proposed to study the influence of initial ovality imperfection on the ultimate bearing capacity of segment lining structure under the external confining pressure. A numerical model was established and verified by the literature experimental data. The geometric calculation theory of ovality imperfection and its value method were analyzed. By introducing the initial ovality imperfections of horizontal long axis and oblique long axis, parameter analysis was carried out to study the effects of different ovality imperfections on the nonlinear stability ultimate loading for shield segments. A method of nonlinear stability ultimate loading for segments with ovality imperfections was put forward. Analysis shows that the initial ovality imperfection has the adverse effect to nonlinear stability ultimate loading for segments and the adverse effect increases by the increase of defect amplitude. For the case of different ovality imperfections, the loading factor increases rapidly, increases gently and tends to converge with the increase of displacement. The variational trend of ultimate loading factor with different ovality imperfections of transverse long axis is summarized. Taking the soil lateral pressure coefficient 0.6 as the critical value, the variational trend experiences slow and rapid increase. Taking the soil resistance coefficient 5.0 MN/m³ as the critical value, the variational trend experiences rapid increase and slow increase. Taking the bending stiffness of the joint 50.0 MN·m/rad as the critical value, the variational trend increases rapidly and tends to be stable. For the case of different ovality imperfections, as the inclined angle increases, the ultimate loading factor improves and the absolute value for corresponding error percentage decreases. The ovality imperfection of transverse long axis is the worst adverse condition. In practical engineering, the reduction coefficient of nonlinear ultimate bearing capacity of segments with ovality imperfection could be considered as 0.85~0.90. The ultimate bearing capacity of the actual lining segment can be approximately solved according to the integral segment considering the reduction coefficient of 0.85.