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Research Article

Design and Construction of a Room-and-Pillar Pilot Underground Space and Evaluation of Roof Deformation by 3D Scan Point-Cloud Comparison

격자형 지하공간 파일럿 테스트의 설계 및 시공과 3D 스캔 점군 비교에 의한 천정부 변형 검토

Chulho Lee12*
이 철호12*
1Member, Professor, KICT　School, University of Science and Technology, 283 Goyang-daero, Ilsanseo-gu, Goyang-Si, Gyeonggi-Do 10223, Republic of Korea
2Member, Senior Researcher, Department of Geotechnical Engineering Research, Korea Institute of Civil Engineering and Building Technology, 283 Goyang-daero, Ilsanseo-gu, Goyang-Si, Gyeonggi-Do 10223, Republic of Korea
*Corresponding Author
30 September 2026. pp. 95-106
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Abstract

The room-and-pillar (grid-type) method forms an underground space by leaving in-situ rock as pillars and allows the space to be expanded during operation. A design procedure based on the strength–stress ratio of pillars and the critical strain of the roof has been proposed in previous studies, but a field-scale space designed by this procedure has not been constructed and its long-term behavior has not been reported. In this study, a pilot room-and-pillar space with four 8 × 8m pillars and 12m wide, 8m high rooms was designed and constructed by drill-and-blast excavation in an operating granite aggregate mine in Gyeongsan, Korea. The roof and pillar surfaces were compared after approximately one year using a photogrammetric point cloud (first epoch) and a terrestrial laser scan (second epoch). Since no absolute control points were available, the two point clouds were registered on the pillar surfaces, and the cloud-to-cloud (C2C) distances along four roof spans between pillars and two central roof profiles were expressed as displacements of the roof relative to the pillars. A level of detection of about 10mm was defined from the specified accuracy of the two sensors and the registration residual on the pillars (±3mm). The space remained unsupported throughout the monitoring period. The relative displacements of the roof spans remained within about ±8mm and those of the pillar faces within ±3mm, all below the level of detection, indicating that no significant deformation of the roof relative to the pillars occurred during the monitoring period. The pillar-based registration and level-of-detection procedure presented in this study is expected to be applicable to long-term monitoring of unsupported room-and-pillar spaces where point-wise instrumentation is impractical.

Keywords
Room-and-pillar method
Pilot test
Terrestrial laser scanning
Photogrammetry
Cloud-to-cloud distance

주방식(격자형) 공법은 원지반 암반을 암주로 남겨 지하공간을 형성하는 공법으로, 운영 중에도 공간을 확장할 수 있다는 특징을 갖는다. 선행 연구에서 암주의 강도응력비와 천정부 한계변형률에 기반한 주방식 지하구조 설계법이 제안되었으나, 이 설계법으로 실제 규모의 공간을 건설하고 장기 거동을 확인한 사례는 보고되지 않았다. 본 연구에서는 경북 경산의 가행 화강암 골재광산에 암주 8 × 8m, 룸 폭 12m·높이 8m의 파일럿 테스트 공간을 설계하고 발파 굴착으로 건설하였으며, 약 1년의 시차를 두고 취득한 사진측량 점군과 지상 레이저 스캔 점군을 비교하여 천정부와 암주면의 형상 변화를 검토하였다. 절대 기준점이 없는 조건이므로 두 점군을 암주면 기준으로 정합하고, 암주 사이 천정부 4개 구간과 중앙부 2개 프로파일의 C2C(cloud-to-cloud) 거리를 암주에 대한 천정부의 상대 변위로 산정하였다. 두 센서의 사양 정확도와 암주면 정합 잔차(±3mm)로부터 약 10mm의 검출 한계를 정의하였으며, 관측 기간 중 공간은 무지보 상태로 유지되었다. 천정부 구간의 상대 변위는 ±8mm 이내, 암주면은 ±3mm 이내로 모두 검출 한계 미만으로 나타나, 관측 기간 중 암주에 대한 천정부의 유의한 변형은 발생하지 않은 것으로 판단되었다. 본 연구에서 제시한 암주면 기준 정합과 검출 한계 산정 절차는 계측기 설치가 어려운 무지보 주방식 지하공간의 장기 모니터링과 정밀 계측 위치 선정에 활용될 수 있을 것으로 기대된다.

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Information
  • Publisher :Korean Geosythetics Society
  • Publisher(Ko) :한국지반신소재학회
  • Journal Title :Journal of the Korean Geosynthetics Society
  • Journal Title(Ko) :한국지반신소재학회 논문집
  • Volume : 25
  • No :3
  • Pages :95-106
  • Received Date : 2026-09-10
  • Revised Date : 2026-09-15
  • Accepted Date : 2026-09-17
  • DOI :https://doi.org/10.12814/jkgss.2026.25.3.095
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