Abstract：Research purposes: The karst tunnel easily becomes the place where the geological disasterhappens during construction of karst tunne,l such as water -inrush and mud -inrush, due to its complexity, changeability and uncertainty. Atpresen,t it isdifficult to accurately forecast the type, position and size of the unfavorable geologicalbody in front of the tunne.l So it is urgent to improve the accuracy of the geological forecast in order to decrease the construction costand casualties asmuch as possible in karst tunnels construction.
Research conclusions:(1)The characteristics and mechanical properties of the karst caves ofQipanshi Tunnel are analyzedwith geological knowledge, and the location and size of the caves in the leftside of tunnelwall are speculated.(2)The ground probing radar is used to probe the left side of tunnelwall and the tunnel bottom, and the probing result shows thata large karst cave exists in the left side of the tunnel and it conforms to the speculated results, except the deviation in position. The reasons for the deviation are analyzed. (3)The comprehensive geological knowledge and geophysical equipmentare two necessary conditions to do the geological forecast perfectly.
2009, Vol. 26 
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