Abstract: Voids behind tunnel linings are a major cause of structural deterioration and can significantly reduce the composite load-bearing performance of the surrounding rock-lining system. As a key embedded component for reinforcement and repair during tunnel operation, the pressure-resistant sealing performance of reserved grouting devices directly governs the effectiveness of post-construction grouting. In this study, four improved grouting-device prototypes were designed and fabricated, and their performance was evaluated through grouting-continuity and sealing tests. The results show that all four device configurations achieve feasible overall structural layouts and enable zoned grouting between the inner and outer sides of the tunnel waterproofing layer. In sealing tests, Device Scheme 1 exhibited pronounced leakage at the zoned-grouting control valve and switching valve, indicating that assembly precision and interface-sealing design require further optimization. Device Scheme 2 incorporated flexible gaskets at the switching valve, effectively mitigating leakage and demonstrating the feasibility of flexible-gasket sealing, though minor leakage persisted at the control valve. Device Scheme 3 improved the connection structure of the control valve by adopting a bottom-bolt radial anchoring design for the exhaust pipe and optimizing gasket materials, successfully achieving the intended sealing and zoned-grouting performance. Device Scheme 4 integrated the control valve, exhaust pipe, and switching assembly into a unified structure, further enhancing sealing reliability. Considering the complexity of tunnel construction environments and the need to balance on-site assembly conditions with overall sealing performance, Device Scheme 3 is comparatively optimal, while actual engineering applications may select among the schemes based on specific project conditions. The experimental results verify that structural refinements and material optimization effectively enhance the sealing performance of reserved grouting devices, providing technical support for their engineering design and broader application in tunnel lining backfill grouting systems.

Key words: Tunnel Lining, Pre-Installed Radial Grouting Device, Zoned Grouting, Penetrability Test, Sealing Test