In the construction of tunnel through karst area due to the concealed caves which in the project could not be taken to safety and often made nonplused susceptible damage to the tunnel construction and that caused a great deal of potential safety problems and greater danger. Because the stability problem caused by mid and small-scale concealed karst cave when tunnel through karst areas is most common

The influence of different scale of crown concealed kast cave and the different distance between the tunnel and the crown concealed kast cave to rock stress

displacement and the internal forces of supporting structure were studied used numerical analytial test method

and the influence of the concealed cave on the tunnel plastic changes of the rock characteristics is also studied. Based on the numerical tests

the tunnel displacement changes inherent mechanism caused by top concealed are proposed. The study shows that within a certain scope of the existing large-scale top concealed cave will lead to increased displacement of the tunnel and the tunnel of rock stress will also increase. The research results of the karst area tunnel have a scientific and quantitative promotion to the design and construction of karst tunnel.