Polymer Foam Mortar for Tunnel Annular Gap Deformation
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Solution Overview
Problem
Existing annular gap mortars in underground tunnel construction exhibit unsatisfactory load-deformation characteristics, leading to high loading of segmental linings during large and time-dependent rock deformations, as they fail to effectively absorb and compress mechanical forces.
Innovation Solution
A mortar mixture is developed for annular gap applications, comprising a hydraulic binder, solid polymer foam particles, and liquid foam, which allows for flexible absorption of mechanical forces in the hardened state, featuring a high volume fraction of polymer foam and a surfactant-based liquid foam for enhanced compressibility and resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional annular gap mortar is used to fill the gap between tubbing lining and rock, then the lining structure is provided, but the mortar cannot effectively absorb mechanical forces during large rock deformations, leading to high loading of the segmental lining
Solution Approach 1:
The patent uses a composite material consisting of cementitious binder and polymer foam particles. The polymer foam particles (expanded polystyrene, polyethylene, or polypropylene) are mixed with the cementitious mortar to create a composite that combines the strength of cement with the compressibility and resilience of foam. This composite structure allows the annular gap filler to maintain load-bearing capacity while providing excellent deformation characteristics, resolving the contradiction between strength and adaptability.
Solution Approach 2:
The invention incorporates polymer foam particles that create a porous structure within the annular gap filler. This porous structure enables the material to compress and deform under rock pressures while maintaining structural integrity. The foam particles act as voids that can be compressed, providing the desired deformation capability without sacrificing the load-bearing capacity provided by the cementitious matrix.
2Strength
If the segmental lining is made sufficiently resistant to counteract high rock pressures, then the lining can withstand forces, but this reaches its limits in the case of large rock deformations
Solution Approach 1:
The patent introduces an intermediary material (the composite annular gap filler) between the tubbing lining and the surrounding rock. This intermediary layer absorbs and cushions the mechanical forces from rock deformations, preventing direct transmission of high stresses to the segmental lining. The foam-cement composite acts as a mediator that provides both structural support and deformation absorption, extending the lining's capability to handle large rock deformations.
3Object-affected harmful factors
If a shock-absorbing intermediate layer is installed, then dynamic effects on cavity construction are reduced, but the load-deformation characteristic remains insufficient for optimal performance
Solution Approach 1:
The patent creates a composite material that combines the shock-absorbing properties of polymer foam with the structural reliability of cementitious binder. This composite provides both the desired shock absorption to reduce dynamic effects from rock deformations and the reliable load-deformation characteristic needed for optimal performance. The synergy between foam and cement ensures both harm reduction and reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The mortar demonstrates optimal compression behavior, capable of withstanding up to 40-50% compression without impairing load-bearing capacity, providing excellent radial deformation properties and reducing the load transferred to the segmental lining, thus enhancing the load-deformation characteristic.
Implementation Method 1
the mortar hardened in a cavity can be deformed or compressed to a certain extent under the influence of mechanical forces
Implementation Method 2
solid particles of at least one polymer foam also being used as Aggregate are included and furthermore at least one liquid foam
Data Source
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AI summary
Mortar, in particular for filling cavities and for the flexible absorption of mechanical forces in the hardened state, comprising at least one binder. It further comprises particles of at least one polymer foam as an aggregate. Additionally, it comprises at least one liquid foam and water.