为保证施工安全，确定围护结构安全冗余度，依托北京某盖挖逆作地铁车站基坑工程，建立基于修正剑桥模型的三维精细化数值模型，在通过现场实测数据验证数值模型合理性的基础上，改变地下连续墙、楼板厚度和立柱直径，分析围护结构参数变化对基坑形变及围护结构抵御连续破坏冗余度变化影响的规律。研究结果表明： 1) 基坑的空间效应及坑角效应的耦合作用导致地下连续墙最大水平位移值分布规律为基坑长边地下连续墙中部水平位移最大、其他位置水平位移值相对较小，基坑短边地下连续墙水平位移最小； 2) 随地下连续墙和楼板厚度变小，地下连续墙深层水平位移逐渐增大，且地下连续墙最大水平位移值的变化量呈指数形式增长，地表沉降值逐渐增大，地表沉降主要发生于2倍基坑深度范围内，2~4倍基坑深度范围内地表沉降已经不显著； 3) 盖挖逆作法施工中楼板相比于明挖法中内支撑刚度更大抵抗变形能力更强，但是围护结构的水平变形仍在一定程度上受到地质条件、结构材料等影响； 4) 墙体厚度和楼板厚度达到1.0 m时，竖向围护结构冗余度趋于稳定，持续增大墙体和楼板厚度对于结构抵御连续破坏的能力不会持续增大。

To ensure the construction safety and determine the safety redundancy of the envelope structure, a threedimensional refined numerical model based on the modified Cambridge model is established based on a metro station foundation pit engineering constructed by covering topdown method in Beijing, China. On the basis of verifying the rationality of the numerical model by the data measured in the field, the thickness of the underground diaphragm wall and the floor slab and the diameter of the column are changed. The influence of the change of the parameters of the envelope structure on the deformation of the foundation pit and the change of the redundancy against continuous damage are analyzed. The results show the following: (1) The coupling effect of the space effect and the pit angle effect of the foundation pit leads to the distribution rule of the maximum horizontal displacement value of the underground diaphragm wall: the horizontal displacement value of the middle underground diaphragm wall of the long side of the foundation pit is the largest, the horizontal displacement value of other positions is relatively small, and the horizontal displacement value of the underground diaphragm wall of the short side of the foundation pit is the smallest. (2) As the thickness of the underground diaphragm wall and floor becomes smaller, the horizontal displacement value of the deep layer of the underground diaphragm wall gradually increases, and the change of the maximum horizontal displacement value of the underground diaphragm wall increases exponentially; the surface subsidence value increases gradually, surface settlement mainly occurs in the range of 2 times the depth of the foundation pit, and the surface settlement in the range of 2~4 times the depth of the foundation pit is no longer significant. (3) The stiffness of the floor in the covering topdown method is greater than that of the inner support in the opencut method, and the resistance to deformation is stronger, but the horizontal deformation of the envelope structure is still affected by the geological conditions and structural materials to a certain extent. (4) When the thickness of the underground diaphragm wall and the floor reaches 1.0 m, the redundancy of the vertical envelope structure tends to be stable, and the continuous increase of the thickness of the underground diaphragm wall and the floor will not increase the ability of the structure to resist continuous damage.