为探明深厚软土地区小尺寸工作井空间效应的影响，提升基坑支护结构设计及计算的合理性，以宁波市通途路盾构法综合管廊工程沿线31座小尺寸工作井深基坑为研究对象，首先，基于基坑几何尺寸、基坑支护结构参数等详细统计数据，系统分析此类基坑的设计现状；然后，采用理论分析与三维有限元模拟相结合的方法，深入研究典型深厚软土地层下小尺寸工作井基坑施工全过程的变形特性；最后，通过建立包含不同基坑长边尺寸的一系列计算模型，定量揭示空间效应的分布规律及其影响范围，并提出小尺寸工作井基坑支护设计的优化策略。研究结果表明： 1）盾构法综合管廊工作井属于典型的小尺寸深基坑工程，在深厚软土地区此类基坑空间效应明显，现有基坑支护结构设计存在优化潜力。2）当基坑长边<25 m时，支护参数优化范围可取为基坑长边、短边全长；当基坑长边≥25 m时，支护参数优化范围可缩减为长边两端各l/3（l为基坑长边）区域及短边全长。3）小尺寸工作井基坑支护结构变形控制的关键在于合理设计地下连续墙厚度，稳定性控制的关键在于足够的地下连续墙插入比。
Examining the impact of spatial effects on the design of small-sized working shafts in deep soft soil regions is crucial for improving the rationality of design and calculation of foundation pit support structures. Herein, case studies are conducted on 31 deep foundation pits of small-sized working shafts along the Tongtu road shield-bored utility tunnels in Ningbo, China. First, based on detailed statistical data including geometric dimensions of the foundation pits and parameters of the support structures, the current design status of such foundation pits is systematically analyzed. Subsequently, a combined approach of theoretical analysis and three-dimensional finite element simulation is employed to thoroughly investigate the deformation characteristics throughout the entire construction process of typical small-sized working shaft foundation pits in deep soft soil strata. A series of calculation models incorporating different long-side dimensions of the foundation pits are established, quantitatively revealing the distribution pattern and influential scope of the spatial effects. Finally, optimization strategies for the support structure design are proposed. The research results indicate that: (1) The working shafts for utility tunnels represent typical deep foundation pits with small dimensions, exhibiting significant spatial effects in deep soft soil regions, suggesting substantial optimization potential in the existing support structure design. (2) The range for optimizing support parameters depends on the long-side dimension: when the long side is ＜25 m, optimization can be applied over the entire length of both the long and short sides; when the long side is ≥25 m, the optimization scope can be effectively reduced to l/3 sections at each end of the long side plus the entire length of the short side （l is side length of foundation pit）. (3) The key factor for deformation control of the support structures is the rational design of the diaphragm wall thickness, while the crucial factor for stability control is ensuring an adequate diaphragm wall embedment ratio.
