Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Liquefaction Resistance of Pohang Sand

포항모래의 액상화 저항 특성에 관한 연구

  • Park, Sung-Sik (Dept. of Civil Engrg., Kyungpook National Univ.) ;
  • Nong, Zhenzhen (Dept. of Civil Engrg., Kyungpook National Univ.) ;
  • Choi, Sun-Gyu (Dept. of Civil and Environ. Engrg., KAIST) ;
  • Moon, Hong-Duk (Dept. of Civil Engrg., Gyeongnam National Univ. of Science and Technology)
  • 박성식 (경북대학교 공과대학 건설환경에너지공학부) ;
  • 농쩐쩐 (경북대학교 공과대학 건설환경에너지공학부) ;
  • 최선규 (한국과학기술원 건설및환경공학과) ;
  • 문홍득 (경남과학기술대학교 건설환경공과대학 토목공학과)
  • Received : 2018.06.12
  • Accepted : 2018.08.20
  • Published : 2018.09.30
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Abstract

A magnitude 5.4 earthquake struck the city of Pohang, North Gyeongsang Province, South Korea on November 15, 2017. Many sand volcanoes were observed on paddy fields, parks and roads. This phenomenon was the first to be observed as a sign of soil liquefaction in South Korea. In this study, two different kinds of ejected Pohang sands were collected from a liquefied paddy field. Those sands were reconstituted into loose and dense conditions and then a series of cyclic simple shear tests were conducted under confining stresses of 100 and 200 kPa. A real earthquake motion was also repetitively applied to the specimen. As a result of constant shear stress tests, the cyclic resistance ratio (CRR) of loose sand was 0.12-0.14, while the CRR value of dense sand was 0.17-0.21. It was shown that the relative density was more influencing factor on liquefaction resistance than the sand types and initial confining stress. When a real Pohang earthquake motion was repetitively applied to the specimen, a loose sand was liquefied at the second earthquake motion but the dense sand at the third earthquake motion.

2017년 11월 15일 경상북도 포항시 흥해읍에서 5.4 규모의 지진으로 논, 공원 또는 도로 등지에서 액상화로 인해 모래와 물이 지표면으로 분출되는 현상이 국내에서 처음으로 발생하였다. 본 연구에서는 포항지역 논에서 분출한 모래를 채취한 다음, 이를 2 종류로 분류하여 이에 대한 반복직접단순전단시험을 실시하였다. 포항모래의 상대밀도에 따른 액상화 거동을 연구하기 위해 느슨하거나 조밀한 상태로 모래를 재성형한 다음 구속응력 100kPa 또는 200kPa를 가한 후 정현파의 반복전단응력을 가하였다. 또한 실제 포항지역에서 계측된 지진파를 실험기기에 입력하여 액상화 발생 여부를 연구하였다. 정현파를 사용한 전단시험 결과 느슨한 시료의 전단저항응력비는 0.12-0.14, 조밀한 시료는 0.17-0.21정도로 조밀한 모래의 액상화 저항력이 느슨한 상태보다 42-50% 정도 높게 나타났다. 모래 종류 및 구속응력보다는 모래의 상대밀도가 액상화 저항력에 더 큰 영향을 미치는 것으로 나타났다. 실지진파를 이용한 전단시험 결과는 구속응력에 관계없이 느슨한 모래의 경우는 2회, 조밀한 모래는 3회 정도의 반복입력 시 액상화가 발생하는 것으로 나타났다.

Keywords

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