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Stability evaluation of rock pillar between twin tunnels using the YAI
Huijian Zhang1, Gongning Liu2, Weixiong Liu1
1Key Laboratory of Transportation Tunnel Engineering, Ministry of Education, School of Civil Engineering, Southwest Jiaotong University, Chengdu, 610031, China.
Scientific Reports
|August 14, 2023
Summary
Rock pillar stability in twin tunnels is vital for safety. Up-down tunnel configurations offer greater stability than left-right layouts, especially with optimized rock pillar thickness to tunnel diameter ratios.
Area of Science:
- Geotechnical Engineering
- Tunneling Engineering
- Civil Engineering
Background:
- Rock pillar stability is critical for the safe construction of twin tunnels with small clearances.
- Transitioning from left-right to up-down tunnel layouts presents unique stability challenges.
- Limited research exists on comparing the stability of rock pillars in these different twin tunnel configurations.
Purpose of the Study:
- To introduce and apply the yield approach index (YAI) for assessing rock pillar stability in small-clearance twin tunnels.
- To comparatively analyze the stability of rock pillars in left-right versus up-down twin tunnel configurations.
- To investigate the influence of side pressure coefficient (SPC), stress release rate (SRR), and rock pillar thickness to tunnel diameter ratio (RPT/TD) on stability.
Main Methods:
- Utilized the yield approach index (YAI) to evaluate rock pillar stability.
- Analyzed the impact of varying side pressure coefficients (SPC).
- Assessed the influence of different stress release rates (SRR).
- Examined the effect of the rock pillar thickness to tunnel diameter ratio (RPT/TD).
Main Results:
- Up-down tunnel configurations exhibit significantly higher rock pillar stability compared to left-right configurations under similar conditions.
- The rock pillar in left-right tunnels is identified as the most vulnerable.
- Up-down tunnels are more sensitive to SPC, while left-right tunnels are more sensitive to SRR.
- Increasing RPT/TD ratio improves stability within the range of 1/4 to 2/3.
Conclusions:
- The stability of rock pillars in up-down twin tunnels is superior to that in left-right configurations.
- The findings provide crucial references for the stability evaluation and design of small-clearance twin tunnels.
- Optimizing RPT/TD is an effective strategy for enhancing rock pillar stability.
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