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Geomechanics and Engineering
  Volume 21, Number 2, April25 2020, pages 171-178

Deformation characteristics of tunnel bottom after construction under geological conditions of long-term deformation
Nag-Young Kim, Du-Hee Park, Hyuk-Sang Jung and Myoung-Il Kim

    Mountainous areas cover more than 70% of Korea. With the rapid increase in tunnel construction, tunnel-collapse incidents and excessive deformation are occurring more frequently. In addition, longer tunnel structures are being constructed, and geologically weaker ground conditions are increasingly being encountered during the construction process. Tunnels constructed under weak ground conditions exhibit long-term deformation behavior that leads to tunnel instability. This study analyzes the behavior of the bottom region of tunnels under geological conditions of long-term deformation. Long-term deformation causes various types of damage, such as cracks and ridges in the packing part of tunnels, as well as cracks and upheavals in the pavement of tunnels. We observed rapid tunnel over-displacement due to the squeezing of a fault rupture zone after the inflow of a large amount of groundwater. Excessive increments in the support member strength resulted in damage to the support and tunnel bottom. In addition, upward infiltration pressure on the tunnel road was found to cause severe pavement damage. Furthermore, smectite (a highly expandable mineral), chlorite, illite, and hematite, were also observed. Soil samples and rock samples containing clay minerals were found to have greater expansibility than general soil samples. Considering these findings, countermeasures against the deformation of tunnel bottoms are required.
Key Words
    tunnel bottom; long-term deformation; tunnel construction
Nag-Young Kim: Institute of Research, Korea Expressway Corporation, Gyeonggido, Korea

Du-Hee Park and Myoung-Il Kim: Department of Civil and Environment Engineering Hanyang University, Seoul, Korea

Hyuk-Sang Jung: Department of Railway Construction and Safety Engineering, Dongyang University, Gyeongbok, Korea

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