Thin Spray-On Liners in Tunnel Engineering
Summary
Thin spray-on liners (TSLs) represent a transformative approach to tunnel support, combining polymer-modified cementitious matrices with rapid pneumatic application to deliver a thin, adherent coating over freshly excavated rock or shotcrete surfaces. Their high early strength and flexibility enable crack bridging, waterproofing and reinforcement in a single operation, reducing labour, formwork and waste compared with traditional steel mesh or thick shotcrete. Modern formulations leverage polymer emulsions—such as vinyl acetate–ethylene copolymers or polyacrylates—to control viscosity, adhesion and curing time, allowing precise adaptation to complex geometries and variable ground conditions. Quality control protocols encompass pre-production trials, rheology measurements and bond tests to ensure consistent performance. Globally, TSLs have been employed for surface support in mining and civil tunnelling, gas migration control in soft ground, and the rapid repair of pre-damaged linings, reflecting their versatility and growing acceptance in underground construction.
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Thin Spray-On Liners in Tunnel Engineering publication trend
The graph below shows the total number of articles in thin spray-on liners in tunnel engineering across all publications each year (not limited to Nature Index journals).
Technical terms
Thin Spray-On Liner (TSL): a polymer-modified cementitious coating applied pneumatically as a thin film for surface support and waterproofing in tunnels.
Shotcrete: concrete or mortar pneumatically projected at high velocity onto surfaces to form a structural lining.
Polymer–Cement Composite: a blend of polymer emulsion and cement designed to enhance adhesion, flexibility and durability of sprayed liners.
Bond Strength: the tensile force per unit area required to detach a liner from its substrate, indicating adhesion performance.
Flexural Strength: the ability of a material to resist bending stress, reflecting its crack-bridging and elastic recovery capabilities.
References
- Material Performance Tests of the Polymer‐Cement Thin Spray‐On Liner. Geofluids (2020).
- Repairing Performance of Polymer-Modified Cement-Based Thin Spray-On Liners on Pre-Cracked Rock-like Specimens. Coatings (2024).
- Study on Antiweathering Support Technology of Thin Spray‐On Liners in Shallowly Buried Coal Seam Roadway under Corrosion Condition. Shock and Vibration (2022).
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