Mud and water gushing happened during the construction in DK262 +411 section of F21 fault in Dananshan tunnel on XiamenShenzhen Railway with the water gushing volume being 60m3/h. The dominant ground in that section is fault breccia consisting of granite, quartzite and diabase, which is subject to becoming mud when water is encountered and has poor stability. A groutstopping wall is designed according to the site conditions and fullface grouting technology, with the grouting boreholes being drilled from the upper semisection, is applied in the tunnel construction to seal off the water and strengthen the ground, which ensures safe tunnelling through the fault section.