Comparison of the RMR Ratings by Tunnel Face Mappings and Horizontal Pre-borings at the Fault Zone in a Tunnel

터널 단층대에서 수평시추와 막장관찰에 의한 RMR값의 비교 분석

  • 김치환 (우석대학교 토목공학과)
  • Published : 2005.02.01

Abstract

The RMR ratings, one by horizontal pre-boring in a tunnel and another by tunnel face mapping, are compared at the fault zone in a tunnel. Generally. the horizontal pre-borings were so effective as to forecast reasonably the supporting patterns after tunnel excavation. But the maximum difference in RMR ratings estimated by two methods was about 50 at a certain section of a tunnel. The differences were analyzed on each parameter of the RMR system: the rating differences were 24 in the condition of discontinuities, 15 in the RQD and 13 in the uniaxial compressive strength of rock. To minimize the gap between RMR by pre-borings and by face mappings, it is necessary to select the horizontal pre-boring location where tunnel stability could be critical and to evaluate in detail the sub-parameters of the condition of discontinuities.

Keywords

rock classification;RMR;fault zone;horizontal pre-boring;tunnel face mapping

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