A Study On Excavation Stability Evaluation And Forecast Of Karst Tunnel

The world’s largest consecutive karst developing area, located in the southwest of China, as a complex and fragile system, is threatening the development of underground engineering, especially for mountain tunnels. Compared with the large-scale karst cave, water gushing and burst mud, people pay less attention to those small-scale karst caves, dissolved cavity and dissolved-fissure, which will cause karst disaster of tunnels such as unsymmetrically loaded and collapse. How to find the timing and method for controlling there karst disaster is still a difficult problem, the correlation techniques and specifications are urgent need.The paper is relied on the import engineering of GuiYang railway terminal, part of GuiGuang line. A survey and analysis has been taken for the karst disaster during the runnel excavation, and finally conclude the major inducement of karst disasters. The mechanical analysis is also used.Based on fussy mathematics, the insitu data and experience, the factor set, evaluate set, membership function set and weight set has been founded. Set up the evaluation index and the fussy evaluate system, apply it to some typical sections of the engineering, compare with the actual excavation and affirm the system’s availability.Choose the different location of the concealed cave, above tunnel, under tunnel and aside tunnel, establish the numerical calculate model for orthogonal experiment with four major factor group:the level of surrounding rock, the depth of tunnel, the diameter and the distance of karst cave. Run regression analysis of experimental data, and set up the quantitative evaluate system, as the assist and supplement for the fussy evaluate system.Apply it to the typical tunnel sections, compare with the actual excavation and affirm the system’s availability.