The use of conventional concrete as the inner lining in double-layer lining shield tunnels presents challenges, including cracking and poor durability. This study proposes a novel double-layer lining structure with Ultra-High Performance Concrete (UHPC) as the secondary lining. The enhancement mechanism of this structure is analyzed through full-scale experiments and refined numerical simulations. The experimental results reveal that, compared to the joints using C30 as the inner lining with a thickness of 20 cm, those with UHPC as the inner lining exhibited an increase in ultimate bearing capacity by 27.23 % and 39.47 % under sagging and hogging moments. Additionally, the initial characterization of the bending stiffness of these joints improved by 21.00 % and 30.06 %. The joints with UHPC as the inner lining exhibited a 29.61 % increase in initial cracking load under sagging moments and a 22.61 % increase in crushing load under hogging moments compared to those with C30 as the inner lining. Notably, the joints with UHPC as the inner lining show lower debonding and slipping between the inner and outer linings. Finally, refined numerical simulations reveal that a 10 cm thick inner lining with UHPC offers a bearing capacity equivalent to that of a 30 cm thick inner lining made of C30, while a 20 cm thick UHPC inner lining exhibits bending stiffness matching that of a 30 cm thick C30 lining. Comparative analyses of different concrete grades and axial forces further highlight UHPC’s significant advantages in enhancing overall structural performance.

中文翻译：

---

UHPC二次衬砌对盾构隧道节理力学性能的增强机理：全尺寸实验与仿真


在双层衬砌盾构隧道中使用传统混凝土作为内衬存在挑战，包括开裂和耐久性差。本研究提出了一种以超高性能混凝土 （UHPC） 为次衬的新型双层衬砌结构。通过全尺寸实验和精细数值模拟分析了该结构的增强机制。实验结果表明，与以 C30 为内衬、厚度为 20 cm 的接缝相比，以 UHPC 为内衬的接缝在下垂和起皱时刻的极限承载力提高了 27.23 % 和 39.47 %。此外，这些接头的弯曲刚度的初步表征分别提高了 21.00% 和 30.06%。与以 C30 为内衬的节点相比，以 UHPC 作为内衬的节点在下垂时刻的初始开裂载荷增加了 29.61%，在磨合时刻的破碎载荷增加了 22.61%。值得注意的是，以 UHPC 作为内衬的接缝在内衬和外衬之间的脱粘和滑动程度较低。最后，精细的数值模拟表明，10 cm 厚的 UHPC 内衬的承载能力相当于 30 cm 厚的 C30 内衬，而 20 cm 厚的 UHPC 内衬表现出与 30 cm 厚的 C30 衬里相当的弯曲刚度。对不同混凝土等级和轴向力的比较分析进一步突出了 UHPC 在提高整体结构性能方面的显著优势。