CHARACTERISTICS ANALYSES OF DEFORMATION AND FAILURE ON TUNNEL SURROUNDING ROCK BASED ON FINE DESCRIPTION OF JOINTS

Jinjishan tunnel in the second stage of Fuzhou airport expressway project is the first multi-arch tunnel with bidirectional eight-lane in China.There were developed joints and crushed rock in tunnel surrounding rock,and the characteristics of joint distribution had significant effect on the stability of tunnel surrounding rock.This paper collected the data of joints in several cross-sections of mid-drift and other outcrop areas of the tunnel,and predicted joints distribution of the main tunnel by using statistical analysis method.On the basis of this,the paper made simulation calculation for the deformation and failure process of the tunnel surrounding rock with the method of discontinuous deformation analysis(DDA).Meanwhile,it divided the typical stages of the deformation and failure process for the tunnel,and also indicated the most possible damaged parts.At last,the paper made a comparison between the result of DDA calculation and practical collapse of Jinjishan tunnel,which were almost the same.Therefore,it is shown that the DDA method is capable of analyzing the stability;and it has good application prospect of stability analysis for tunnel surrounding rock.