针对大卵石地层盾构施工的难点，从地质适用性、结构可维护性、自身性能特点、处理大卵石或孤石的优势、施工安全性与质量、施工速度等方面进行分析，阐述开敞式盾构机的可行性，给出了北京地铁开敞式盾构设计方案及施工工艺；针对大砂卵石地层中盾构施工，从掘进速度、经济特性、综合性能等方面对土压平衡盾构机与开敞式盾构机进行了对比，表明了在大卵石地层采用开敞式盾构机是值得考虑的。

 Focusing on the challenge of boring in cobblecontained ground, the authors make feasibility study on application of open shield in construction of Beijing Metro tunnels in cobblecontained ground in terms of geological adaptability, structural maintainability, performance, advantages in coping with large cobbles and boulders, construction safety and quality and boring speed. The authors propose the design and boring techniques of open shield for Beijing Metro works. Regarding boring in cobblecontained ground, the authors make comparison and contrast between EPB shield and open shield in terms of boring speed, economical index and comprehensive performance. The authors conclude that it is worth to take open shield into consideration in the selection of proper shields for cobblecontained ground.