The stability of the shield tunneling face is an extremely important factor affecting the safety of tunnel construction. In this study, a transparent clay with properties similar to those of Tianjin clay is prepared and a new transparent clay model test apparatus is developed to overcome the “black box” problem in the traditional model test. The stability of the shield tunneling face (failure mode, influence range, support force, and surface settlement) is investigated in transparent clay under active failure. A series of transparent clay model tests is performed to investigate the active failure mode, influence range, and support force of the shield tunneling face under different burial depth conditions, whereas particle flow code three-dimensional numerical simulations are conducted to verify the failure mode of the shield tunneling face and surface settlement along the transverse section under different burial depth conditions. The results show that the engineering characteristics of transparent clay are similar to those of soft clay in Binhai, Tianjin and satisfy visibility requirements. Two types of failure modes are obtained: the overall failure mode (cover/diameter: C/D ⩽ 1.0) and local failure mode (C/D ⩾ 2.0). The influence range of the transverse section is wider than that of the longitudinal section when C/D ⩾ 2.0. Additionally, the normalized thresholds of the relative displacement and support force ratio are 3%–6% and 0.2–0.4, respectively. Owing to the cushioning effect of the clay layer, the surface settlement is significantly reduced as the tunnel burial depth increases.

盾构隧道施工面的稳定性是影响隧道施工安全的极为重要的因素。在这项研究中，制备了一种性能与天津粘土相似的透明粘土，并开发了一种新的透明粘土模型测试设备来克服传统模型测试中的“黑匣子”问题。研究了主动破坏下透明黏土中盾构隧道面的稳定性（破坏模式，影响范围，支撑力和表面沉降）。进行了一系列透明黏土模型测试，以研究在不同埋深条件下盾构隧道工作面的主动破坏模式，影响范围和支撑力，进行了粒子流代码三维数值模拟，以验证在不同埋深条件下盾构隧道掘进面的破坏模式和沿横截面的表面沉降。结果表明，透明黏土的工程特性与天津滨海的软黏土相似，并且满足可见性要求。获得两种类型的故障模式：整体故障模式（盖/直径：C / D⩽1.0）和本地故障模式（C / D⩾2.0）。当C / D≥2.0时，横截面的影响范围比纵向横截面的影响范围宽。此外，相对位移和支撑力比率的归一化阈值分别为3％–6％和0.2–0.4。由于粘土层的缓冲作用，随着隧道埋藏深度的增加，地表沉降明显减少。