以局部破碎带的某海底岩体隧道为例，采用有限元极限分析法分析了海底隧道岩体注浆加固前后的稳定性。计算表明，对于整体较为安全的隧道，当存在局部破碎带时，安全度降低，破碎带越宽，注浆堵水圈厚度越小，安全系数越小。与完整围岩破裂面位于两侧相比，含倾角45°破碎带围岩的堵水部分最先失稳。因此，必须做好破碎带的超前注浆堵水，以减少其渗水量，并对破碎带进行局部加固，此种情况下，隧道衬砌原则上可按无水压设计，衬砌厚度与采用全水头设计相比可以大大降低。

Considering the sea water seepage, limit analysis by finite element method is used in a subsea tunnel to analyze the stability before and after grouting reinforcement. Results show that the faultrupture zone decreases the stability of tunnel. The wider the faultrupture zone is, the more unsafe the tunnel is. The more thickness the grouting loop is, the safer the tunnel is. And the faultrupture zone with slip surface of 45° tends to lose stability most. The width of subsea tunnel lining must increase, if the full seepage pressure is considered in the design of tunnel.