The intersection vertical interval between Zhongliang Mountain tunnel of Chengdu-chongqing highspeed railway and existing business line tunnel is only 2.7 m.In order to perform the tunnel construction successfully,the reinforcement to existing business line tunnel was applied during the idle period with I20b steel by using the three-drilling method in the installation of foot bolt and feet-lock bolt.According to the characteristics of surrounding rock,the mechanical excavation with controlled blasting method was used,and the No.2 emulsion explosive with lowdetonation velocity was chosen as blasting source,finally,the maximum blasting vibration velocity,the vault subsidence and the horizontal convergence values are all controlled within the permissible range.%成渝高铁新中梁山隧道与既有营业线交叉段竖向净距仅为2.7m,为顺利完成隧道建设,对既有营业线路隧道利用“天窗”期采用I20b型钢进行加固,并运用“三次钻进法”完成了钢拱架脚底螺栓和锁脚锚杆的安装.根据围岩情况隧道采用机械开挖和非爆法加控制爆破法进行施工,通过计算采用低爆速2号岩石乳化炸药进行爆破,使得最大爆破振速、拱顶沉降值、水平收敛值均在规范允许变化范围内.
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