大瑞铁路高黎贡山平导隧道TBM在掘进过程中遭遇断层破碎带地层，发生3次较严重的卡机事故。为降低施工风险，加快施工进度，节约施工成本，采用调研、工程对比与专家论证的方法，分析刀盘被卡的原因，研究护盾延伸的必要性与可行性，制定护盾延伸方案，即将护盾与刀盘的间距由原来的360 mm缩减为50 mm。实践表明： 护盾延伸改造效果明显，在Ⅳ、Ⅴ级围岩实际占比达到67%的情况下，继续掘进近1 500 m，未再发生卡机事故，大大提高了TBM的掘进效率。

Three serious jam accidents occurred to TBM when boring in parallel adit of Gaoligongshan Tunnel on DaliRuili Railway in fault and fractured zone. In order to reduce the construction risk, speed up the construction schedule and save the construction cost, the causes for cutterhead jam are analyzed, and the necessity and feasibility of shield extension are studied by means of investigation, engineering analogy and expert argumentation; and then, the shield extension scheme is developed, i.e. the space between shield and cutterhead is shorten from 360 mm to 50 mm. The practices show that under the proportion of grade Ⅳ and Ⅴ surrounding rocks reaching 67%, jamming accident does not occur when TBM continues to tunneling about 1 500 m, the tunneling efficiency is improved greatly and the effect of shield extension is remarkable.