| Due to the geological complexity and concealment of deeply-buried long tunnels, it is usually difficult to predict occurance of geological hazards, posing risks on the safety of construction. This paper, based on Daxiangling Tunnel Project along Ya’an-Lugu Expressway, conducts comparison study on advance geological forecast methods for geological disasters including surrounding rock classification, rockburst, landslide, large deformation and water outburst and mud outburst of Daxiangling Tunnel.Based on analysis of previous experience and technologies from both China and other countries, this paper identifies the engineering geological condition of Nibashan Tunnel, and finds out its main types of geological hazards, disaster mechanism and distribution pattern. After analyzing conventional forecasting methods, the paper brings forward evaluation indexes and ratings of geological disasters that commonly happen in tunnel construction, like surrounding rock classification, rockburst, landslide, large deformation and water outburst and mud outburst. And then it establishes the fuzzy comprehensive assessment system and the matter-element analysis system for advance geological forecast, and compares these two systems with conventional forecasting methods. Compared with the actual excavation, the matter-element forecast reaches an accuracy rate of81.7%, and the forecast of the fuzzy comprehensive assessment system registers an accuracy rate of78.3%, which are much higher than that of the conventional forecasting methods.The success of the smart forecasting system in Nibashang Tunnel Project is an application of tremendous significance for similar engineering projects, which provides more reliable predictions and more convenience for excavation safety and surrounding rock stability in tunnel construction. |
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