中文摘要：

以外径10.8m的大断面盾构隧道为研究对象,针对标准贯入度N≤5的软弱黏土地层条件,进行盾构隧道管片衬砌结构的失稳破坏模型试验,分析拼装方式、接头抗弯刚度、管片刚度、地层空洞及地层改良对盾构隧道稳定性的影响,探明盾构隧道的失稳破坏形态。结果表明,与增强管片结构刚度措施相比,地层改良更能显著提高盾构隧道的稳定承载力;地层空洞的存在加剧了管片衬砌的失稳,空洞位置越靠近隧道拱腰水平位置,盾构隧道的稳定性越差;从提高盾构隧道的稳定性方面考虑,建议采用错缝拼装方式、刚性管片接头,并避免管片缺陷的产生。盾构隧道失稳是管片衬砌结构强度破坏与整体刚度降低耦合发展的结果。在无管片缺陷、无地层空洞情况下,盾构隧道失稳时的管片衬砌最大单点位移80~140mm,椭圆扁平率2%~5%,可为外径10m级盾构隧道失稳判定提供参考。

英文摘要：

With the shield tunnel with large cross-section of 10. 8m outer diameter as the research object, a model test on the instability failure for segment lining structure of shield tunnel was carried out under the soft clay strata conditions with standard penetration degree of being less than or equal to 5. The influence of the assembling mode, joint bending stiffness, segment stiffness, strata cavity and strata improvement on the stability of shield tunnel was analysed to prove the instability of shield tunnel. The study shows as follows： compared with the measure to enhance segment structure stiffness, strata improvement can significantly increase the stability bearing capacity of shield tunnel. The existence of the strata cavity aggravates the instability of segment lining. The closer the position of the strata cavity is to the arch waist level position of the tunnel, the worse the stability of shield tunnel is; From the perspective of improving the stability of shield tunnel, the staggered joint assembling mode and rigid joints are recommended to use, and segment defect generation should be avoided . The instability of shield tunnel is the result of the coupling development result of the failure of segment lining structure strength and stiffness decreasing. In the case of no segment defect or no strata cavity, the maximum displacement of the segment lining is 80- 140mm, the elliptic flat rate is 2%- 5% when shield tunnel loses stability. It can provide references for instability judgment on shield tunnels of 10m outer diameter.