REFERENCES
- Bieniawski , Z. T. 1989 . Engineering rock mass classifications 51 – 63 . John Wiley & Sons .
- Coal Industry Promotion Board . 319 Investigation of ground stability in Munkyong area, pp. (in Korean)
- Im , S. B. , Lee , C. B. and Kim , D. S. 1993 . “ Survey of geology and coal in Samchok and Bekbyongsan area (XI) ” . In KIGAM Report, KR-92–6A-1, pp.101, (in Korean)