Journal of Korean Tunnelling and Underground Space Association (한국터널지하공간학회 논문집)

Korean Tunnelling and Underground Space Association (한국터널지하공간학회)
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Effect of RMR and rock type on tunnel drilling speed

RMR과 암석종류가 터널 천공속도에 미치는 영향

  • Kim, Hae-Mahn (Dept. of Civil, Environmental, and Architectural Engineering, Korea University) ;
  • Lee, In-Mo (Dept. of Civil, Environmental, and Architectural Engineering, Korea University) ;
  • Hong, Chang-Ho (Dept. of Civil and Environmental Engineering, KAIST)
  • 김해만 (고려대학교 건축사회환경공학부) ;
  • 이인모 (고려대학교 건축사회환경공학부) ;
  • 홍창호 (한국과학기술원 건설및환경공학과)
  • Received : 2019.05.22
  • Accepted : 2019.06.21
  • Published : 2019.07.31
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Abstract

Drilling and charging of the blast holes during NATM tunneling works take more than 30% of construction time among the whole tunneling work process. Prediction of ground condition ahead of tunnel face has been studied by several researchers by correlating percussion pressure and drilling speed during tunneling work with the ground condition and/or RMR values. However, most of the previous researches were conducted in the granite rock condition which is the most representative igneous rock in the Korean peninsula. In this study, drilling speeds in igneous rocks were analyzed and compared with those in sedimentary rocks (most dominantly composed of conglomerates, sandstones, and shales) under the similar RMR ranges; it was identified that the drilling speed is pretty much affected by rock types even in a similar RMR range. Under the similar RMR values, the drilling speed was faster in sedimentary rocks compared with that in igneous rock. Moreover, while the drilling speed was not much affected by change of the RMR values in igneous rocks, it became faster in sedimentary rocks as the RMR values got lower.

NATM 공법을 이용한 터널굴착 시 발파공 천공 및 장약 작업은 전체 터널 굴착 시간의 30% 이상을 차지하는 중요한 과정이다. 최근에는 이 공정을 활용하여 천공작업 도중 얻어지는 타격압, 천공속도 등을 바탕으로 터널 굴착면 전방의 지반상태, RMR 등을 예측하는 연구들이 진행되어 왔다. 하지만 선행 연구들은 대부분 화강암으로 대표되는 화성암질 지반에 대해서만 수행되어 왔다. 본 연구에서는 유사한 RMR의 범위를 가지는 화성암의 천공속도를 퇴적암(특히, 역암, 사암 및 셰일)의 천공속도와 비교/분석하였으며, 유사한 RMR 값을 가지는 암이라 하더라도 암질 종류에 따라서 천공속도가 크게 달라질 수 있음을 확인하였다. 퇴적암에서의 천공속도가 화성암에서의 속도보다 더 빨랐으며, 또한 화성암의 경우 천공속도와 RMR등급에 따른 천공속도의 차이는 거의 없는 것에 반하여, 퇴적암의 경우는 RMR등급이 낮아질수록 천공속도는 증가함을 알 수 있었다.

Keywords

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Fig. 1. Jumbo drill utilized in this study

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Fig. 2. Test sites

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Fig. 3. Sectional view of the tunnels and measured sections

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Fig. 4. Acquisition of average drilling speed (underground manager)

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Fig. 5. Drilling process

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Fig. 6. Drilling speed with different RMR

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Fig. 7. Drilling speed with different types of rock and RMR class

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Fig. 8. Sandstone near the tunnel site B

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Fig. 9. Relationship between RMR and drilling speed

Table 1. Specification of jumbo drill (Atlas Copco XL3C & COP 2238)

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Table 2. Summarization of the obtained data

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