In room-and-pillar mining method which is commonly adopted for underground limestone mine in Korea, the design of safety pillar is very important for securing a safety in mining operation as well as for preventing a collapse in roof. It is known that the stability of safety pillar in underground mine openings is mainly determined by characteristics of rock and discontinuities during mining process and also affected by time-dependent weathering characteristics of rock after completion of mining operation.
For analyzing the effect of time-dependent weathering characteristics of rock on pillar stability, in this study, a freeze-thaw test for Poongchon limestone obtained from underground limestone mine has been implemented in temperature range of -18 ~ +4? for simulating the weathering process. Changes in physical and mechanical characteristics of rock and discontinuities are determined from artificial weathering test and used for numerical analysis on time-dependent pillar stability.
Mining methods are being changed recently from surface mining method to underground mining method, for reasons of increment of environmental issues in Korea. For underground mining operations, therefore, the room-and-pillar mining method has been commonly adopted in underground limestone mine in Korea. Considering a room-and-pillar method in underground limestone mine, safety pillar designing should be reflected on long-term stability and its weakening process should be also reviewed by chemical and physical weathering (Chatterji and Christensen, 1979; Goudie, 1999; Hanja, 2003; Park and Park, 2015).
For analyzing the effect of time-dependent weathering characteristics of rock on pillar stability, in this study, a freeze-thaw test on Poongchon limestone from underground limestone mine was performed in temperature range of -18 ~ +4? for simulating the physical weathering process. The artificial weathering test by a freeze-thaw test deduced changes in several physical properties such as density, absorption, elastic wave velocity, shore hardness, and shear strength of rock mass. These results were used for numerical analysis on time-dependent stability of safety pillar.
