(1. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China；2. Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education，Tongji University，Shanghai 200092，China；3. Fujian Electric Power Survey and Design Institute，Fuzhou，Fujian 350003，China)
Abstract：Jinjishan tunnel in project of Fuzhou airport expressway construction is multi-arch tunnel with eight lanes in China. In surrounding rock of the tunnel，joints were developed which cut the original rock blocks into even smaller blocks. The blocks can be easily disturbed and become unstable during tunnel excavation. To keep the blocks stable is one of the most important problems in construction of the highway tunnel. Data of joints unveiled during excavation in several cross-sections of mid-drift of the tunnel and other areas are collected in detail and described meticulously. Based on statistical analysis of the data，distribution of joints in whole face tunnel relative to the same cross-section is forecasted. The block theory is adopted to study the location，volume，sliding force，safety factor and other parameters of key blocks in the cross-sections of whole face tunnel. Mechanical calculations of stability are performed to analyze the key blocks in different situations which are the none of reinforced situation，reinforced by anchors situation，and reinforced by anchors and shotcrete situation. The situations are evaluated and advices are made for the engineering application of the tunnel.
