A study on asymmetric load on circular shaft due to engineering characteristics of discontinuous rock masses

Young-Wan* Shin; Kyoung-Sun Moon; Kyoung-Won Joo

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2008 Vol.10, Issue 2 Preview Page Next Page

A study on asymmetric load on circular shaft due to engineering characteristics of discontinuous rock masses 불연속암반의 공학적 특성에 따른 원형수직구 편하중에 관한 연구

30 June 2008. pp. 119-128

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Abstract

In the case of a circular shaft, it is expected that asymmetric loads should apply on the surface rather than symmetric loads due to geographical factors and the non-homogeneity of the jointed rock masses. In this study, discontinuous numerical analysis was carried in order to analyze the characteristics of asymmetric load distribution on the wall of the circular shaft due to anisotropy caused by heterogeneity of rock masses affected by the discontinuities like as a joint. And it was also analyzed that the effect of the mechanical properties varied with the rock mass rating and horizontal stress with depth had influence in the asymmetric load on the wall of the shaft. In the case of considering the effect of the joint as variable, asymmetric load ratio (Rp), which was defined as the ratio of the load subtracted minimum from maximum to minimum, was below 25% in the hard rock. As regarding the variation of the rock mass rating with depth as variable, the value of Rp was below than 25% in the hard rock, and the value between 30% and 40% in the soft rock. On the other hand, the Rp of fractures rock was between 45～50% which value was much higher than that in better rock mass rating.

Keywords

Circular shaft

jointed rock mass

heterogeneity

anisotropy

asymmetric load

원형수직구의 경우 지형적인 요인과 지반의 불균질성으로 인하여 등분포의 대칭하중이 작용하는 경우보다는 비대칭의 편하중이 작용하는 경우가 많을 것으로 예상된다. 지금까지 지반조건에 따른 원형수직구 벽체에 작용하는 편하중 산정을 위한 정량적인 연구는 미흡한 실정이다. 본 연구에서는 불연속암반의 불균질성을 고려한 불연속체 해석을 통하여 이방성 거동에 따른 원형수직구 벽체에 작용하는 편하중 분포특성을 분석하였다. 또한, 깊이에 따른 암반등급 및 초기응력이 편하중에 미치는 영향을 분석하였다. 검토 결과 절리특성에 따라 양호한 경암반에서는 25%이하의 편하중이 발생하는 것으로 분석되었으며, 수직구 깊이에 따른 암반등급의 영향을 검토한 결과 경암의 편하중비는 25%이하, 연암에서는 30%∼40%로 나타났다. 또한, 풍화가 진행된 파쇄연암의 편하중비는 40%∼50%로 나타났다. 깊이 100 m의 경암반에 대하여 초기응력을 나타내는 측압계수(Ko)를 변수로 한 불연속체 해석을 수행하였다. 해석 결과 측압계수가 2.0보다 작은 경우의 편하중비는 약 25%의 값을 나타내나 측압계수가 2.0보다 큰 경우에는 편하중비가 점차 증가하는 경향을 나타냈다.

키워드

원형수직구

불연속암반

불균질성

이방성

편하중

References

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Information

Publisher :Korean Tunneling and Underground Space Association
Publisher(Ko) :한국터널지하공간학회
Journal Title :Journal of Korean Tunnelling and Underground Space Association
Journal Title(Ko) :한국터널지하공간학회 논문집
Volume : 10
No :2
Pages :119-128

Journal of Korean Tunnelling and Underground Space Association ISSN:2233-8292(Print) 2287-4747(Online) 한국터널지하공간학회 논문집

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