Segment-Lined Tunnel Construction for Overlapping Excavation
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Solution Overview
Problem
The construction times of natural tunnels using the 'traditional' excavation technique are limited by the sequential and labor-intensive nature of operations, which are significantly influenced by workforce experience and skill, and the final lining process obstructs excavation progress.
Innovation Solution
A method involving simultaneous advancement of the excavation and final lining fronts using prefabricated segments assembled by a segment placing machine, allowing the final lining to be built mechanized and overlapping with excavation, reducing the need for repeated machine passage through the tunnel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the final lining is built using traditional concrete casting with formwork, then the tunnel structure is stabilized, but the excavation progress is obstructed and construction time is extended
Solution Approach 1:
The final lining is divided into prefabricated segments that can be assembled in discrete units. This allows the lining to be pre-manufactured outside the tunnel and then quickly installed, eliminating the need for time-consuming on-site concrete casting operations and formwork assembly/disassembly, thus resolving the contradiction between structural stability and construction time
Solution Approach 2:
The lining segments are pre-manufactured and prepared before being installed in the tunnel. This preliminary action allows the lining to be ready for immediate installation, eliminating the waiting time associated with on-site concrete curing and formwork operations, thereby reducing overall construction time while maintaining structural reliability
2Productivity
If operating machines and vehicles pass through the tunnel repeatedly to reach the working front, then the excavation can be advanced, but the construction time is extended due to repeated passage requirements
Solution Approach 1:
The final lining is pre-installed at the working front before excavation machines need to pass through. This preliminary installation eliminates the need for machines to pass through the tunnel repeatedly to reach the working front, as the lining is already in place to guide and protect the excavation advance, thus reducing machine passage time and improving productivity
Solution Approach 2:
The prefabricated lining segments act as an intermediary structure that is installed first to create a stable pathway. This intermediary lining allows subsequent excavation machines to move through the tunnel more efficiently without needing to repeatedly pass through unstable or unlined sections, thereby reducing the time lost to repeated machine passages
3Reliability
If the final lining process is completed before excavation can resume, then the tunnel structure is stabilized, but the excavation advance is blocked
Solution Approach 1:
The final lining is segmented into modular units that can be installed progressively at the working front. This segmentation allows the lining to be advanced simultaneously with excavation operations, enabling both structure stabilization and excavation progress to occur in parallel rather than sequentially, thus resolving the contradiction between reliability and productivity
Solution Approach 2:
The installation of lining segments and the advancement of excavation fronts are performed continuously and simultaneously. This continuous action ensures that the lining is always being advanced to match the excavation progress, maintaining both structural stability and excavation speed without blocking the excavation advance
Data Source
AI summary
A method for constructing natural tunnels including advancing an excavation front of a tunnel by a predetermined advance length via point excavation with excavating machines, removing excavated material from a work region between the excavation front and a final lining front of the tunnel, applying a primary lining onto walls exposed by the excavation at the advance length of the excavation front, advancing the final lining front by a predetermined advance length by creating a final lining on the primary lining applied at the same advance length in a previous advance cycle, and repeating all steps until the tunnel is completed. The step of advancing the final lining front is carried out with a segment placing machine having a tubular frame. Passage or displacement of operating machines, vehicles, or equipment from/to the work region during the steps of removing and applying takes place through the tubular.