Geomechanics and Engineering

Techno-Press (테크노프레스)
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Discrete element numerical analysis for simulating trapdoor tests to assess loosening earth pressure on tunnel linings

  • Chaemin Hwang (School of Civil, Environmental and Architectural Civil Engineering, Korea University) ;
  • Junhyuk Choi (Civil Overseas Engineering Team, Daewoo Engineering & Construction Co., Ltd.) ;
  • Jee-Hee Jung (Korea Expressway Corporation Research Institute) ;
  • Hangseok Choi (School of Civil, Environmental and Architectural Civil Engineering, Korea University)
  • Received : 2023.11.23
  • Accepted : 2024.02.23
  • Published : 2024.09.25
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Abstract

Concrete linings in tunnels constructed by drilling and blasting such as NATM serve as a secondary support structure. However, these linings can face unexpected earth pressures if the primary support deteriorates or if ground conditions become unfavorable. It is crucial to determine the loosening earth pressure that allows the lining to maintain its structural integrity and prevent damage caused by this pressure. This study proposes a numerical model for simulating the trapdoor test and developing a method for calculating the loosening earth pressure. The discrete element method (DEM) was employed to describe the soil characteristics around the tunnel. Using this numerical model, a sequence of experimental trapdoor steps was simulated, and the loosening earth pressure was analyzed. Contact parameters were calibrated based on an analysis of a triaxial compression test. The reliability of the developed model was confirmed through a comparison between simulation results and laboratory test findings. The model was used to calculate the contact force applied to the trapdoor plate and to assess the settlement of soil particles. Furthermore, the model accounted for the soil-arching effect, which effectively redistributes the load to the surrounding areas. The proposed model can be applied to analyze the tunnel's cross-sectional dimensions and design stability under various ground conditions.

Keywords

Acknowledgement

This research was conducted with the support of the "National R&D Project for Consecutive Excavation Technological Development Project of Tunnel Boring Machine (RS-2022-00144188)" funded by the Korea Agency for Infrastructure Technology Advancement under the Ministry of Land, Infrastructure and Transport, and managed by the Korea University.

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