Fig. 1. Illustration of stress release zone during tunnel excavation and stress release zone determination (modified after Xu et al., 2018)
Fig. 2. Mechanism of restoration for ground cavity with inserting of expansive material
Fig. 4. Laboratory tests of expansive material; (a) uniaxial compression, (b) expansion ratio, (c) temperature effect and (d) expansion pressure test
Fig. 3. Brief chemical equation of urethane reaction process (modified after Kim and Youn, 2009)
Fig. 5. Assumption of stress release zone when cavity was occurred in this study
Fig. 6. Composition of experiment equipment capable simulating of stress release zone; (a) combination with each part (b) mold, (c) load cell attached spring and (d) frame for fixing
Fig. 7. Principle of experiment equipment capable simulating of stress release zone
Fig. 8. Experiment procedure: (a) Pour the half of sands, (b) insertion of expansive material into equipment, (c) installation of part containing load cell and spring after pour of the remaining half of the sands, and (d) measurement of sand-expensive material mixture
Fig. 9. Results of experiment: Variation of average expansion pressure with (a) time and (b) displacement (spring coefficient = 148.764 kN/m)
Fig. 10. Relationship between thermal strain and temperature given in ABAQUS/CAE (modified after SIMULIA, 2014)
Fig. 11. Result of thermal expansion analysis: (a) Numerical model and (b) Ratio of expanded-to-initial volume with increasing thermal expansion coefficient
Fig. 12. Result of uniaxial compression analysis: (a) Numerical model and (b) uniaxial compression strength with increasing elastic modulus (Poisson's ratio = 0.3)
Fig. 14. Modeling of experiment equipment capable simulating of stress release zone
Fig. 15. Displacement field of soil and expansive material after expansion based on the model represented in Fig. 14
Fig. 16. Behavior after expansion according to the volume ratio of the expansion material to the cavity: Increased volume in percentile : (a) 1.7%, (b) 10.5%, (c) 23.6% and (d) 41.9%
Fig. 17. Variation of (a) maximum expansion pressure and (b) average compressive strain with increasing spring coefficient
Fig. 18. Variation of (a) maximum expansion pressure and (b) average compressive strain with ratio of width and height (W/H)
Fig. 13. (a) boundary condition of experiment capable simulating of stress release zone: (a) Numerical modeling and (b) result and plot after numerical analysis
Table 1. Laboratory test for expansion material
Table 2. Results with volume ratio of the expansion material to the cavity
References
- Chun, B. S. (1997), "The Engineering Properties and Effectiveness of Polyurethane for Ground Reinforcement", Journal of The Korean Society of Civil Engineers, Vol.17, No.3_4, pp.475-475. (in Korean)
- Han, Y. S. (2017), "Complex Detect system for the Underground Cavern and Object Detect", Journal of the Korean Geosynthtic Society, Vol.16, No.4, pp.6-12. (in Korean)
- Kim, C. Y., Jung, J. H., Choi, C. H. and Woo, W. G. (2015), "Cause of Ground Subsidence (Sink Hole), Technical and Policy Response Direction", Research Institute of Ssanyong Engineering and Construction, Vol.71, pp.17-25. (in Korean)
- Kim, H. S. and Youn, J. W. (2009), "A Study on Foaming Characteristics of Polyurethane depending on Environmental Temperature and Blowing Agent Content", Transactions of Materials Processing, Vol.18, No.3, pp.256-261. (in Korean) https://doi.org/10.5228/KSPP.2009.18.3.256
- Kim, J. B., You, S. K., Han, J. G., Hong, G. G. and Park, J. B. (2017), "A Study on Simulation of Cavity and Relaxation Zone Using Laboratory Model Test and Discrete Element Method", Journal of the Korean Geosynthtic Society, Vol.16, No.2, pp.11-21. (in Korean)
- Kuwano, R., Sato, M. and Sera, R. (2010), "Study on the detection of underground cavity and ground loosening for the prevention of ground cave-in accident", Japanese Geotechnical Journal, Vol.5, No.2, pp.219-229. https://doi.org/10.3208/jgs.5.219
- Lee, K., Choi, B. G., Park, J. and Kim, D. (2018), "Numerical Analysis and Laboratory Experiment of Rapid Restoration of Underground Cavity Using Expansive Material without Excavation", Journal of the Korean Geosynthtic Society, Vol.17, No.1, pp.55-64. (in Korean)
- Lee, S. M. and Yoon, H. M. (2017), "A Study for Improvement of Policy on Ground Subsidence Prevention in Urban Areas", Seoul Studies, Vol.18, No.1, pp.27-42. (in Korean)
- Sahebi, A., Jalalifar, H., Ebrahimi, M. and Abdolrezaee, A. (2010), "Stability Analysis of Tabas Coal Mine Roadway using Empirical and Numerical Methods", 2010 Underground Coal Operators' Conference, pp.125-134.
- Sato, M. and Kuwano, R. (2010), "Model Tests for the Evaluation of Formation and Expansion of a Cavity in the Ground", In Proc. of 7th International Conference on Physical Modelling in Geotechnics, pp. 581-586.
- Seoul City (2016), Road collapse management comprehensive counter measures reporter briefing, Seoul City. (In Korean)
- SIMULIA (2014), ABAQUS/CAE User's Manual, Dassault Systemes Simulia Corp., Providence, RI, USA.
- Singh, B. and Goel, R. K. (2011), Engineering Rock Mass Classification, Butterworth-Heinemann.
- Whittaker, B. N. and Hodgkinson, D. R. (1971), "The Influence of Size on Gate Roadway Stability", The Mining Engineer, Vol.130, pp.203-213.
- Xu, D. P., Zhou, Y. Y., Qiu, S. L., Jiang, Q. and Wang, B. (2018), "Elastic Modulus Deterioration Index to Identify the Loosened Zone around Underground Openings", Tunnelling and Underground Space Technology, Vol.82, pp.20-29. https://doi.org/10.1016/j.tust.2018.07.032
- Yu, N. J., Choi, J. H. and Lee, K. I. (2017), "Fundamental study on the development of Filling materials for Trenchless Emergency Restoration of Ground cavity", Journal of the Korean Geosynthtic Society, Vol.16, No.2, pp.97-107. (in Korean)