摘要
随着地下空间进一步的开发与利用,盾构施工面临的地质条件更加复杂多样。盾构在复合地层中掘进时,因地层间力学性质差异,易因开挖面支护力确定不当而造成失稳破坏,给工程带来负面影响。针对盾构隧道穿越复合地层较穿越均质土体时,由于上下地层间力学性质差异而导致的开挖面支护压力难以确定的问题,基于组合对数螺旋线破坏模式的复合地层中盾构开挖面失稳模型,利用极限分析上限定理推导了复合地层盾构隧道开挖面极限支护力上限表达式,结合非线性优化技术,求得极限支护力最优解,并通过与现有文献进行对比,验证了采用组合对数螺旋破坏模式的合理性;同时,讨论了不同参数对极限支护力及临界破坏模式的影响,给出了破坏时临界滑动面示意图。结果表明:当上部地层内摩擦角和黏聚力一定,极限支护力随下部地层内摩擦角和黏聚力的增大而降低;随着隧道直径的增大,极限支护力显著增大。定义上层地层深度与隧道直径之比为深度系数,对于复合地层,深度系数越小,极限支护力对于地层抗剪强度参数的变化越敏感;但对于单一地层,深度系数的变化对极限支护力没有影响。所得结论对实际工程具有一定的指导意义。
With the further development and utilization of underground space,the geological conditions faced by shield tunneling are more complex and diverse.When the shield tunnels in the composite strata,due to the differences in mechanical properties between the strata,it is easy to cause instability and damage due to improper determination of the supporting force of the excavation surface,which will bring negative impacts to the projects.It is difficult to determine the support pressure of the excavation face due to the stiffness differences between the upper and lower strata,when the shield tunnel passes through the composite strata.Based on the combined logarithmic helix failure model utilized as the instability model of the shield excavation face in the composite strata,the upper limit expression of the limit support force of shield excavation face in the composite strata was derived by using the upper bound theorem of limit analysis.The optimal solution of the ultimate support force was obtained by linear optimization technology,and the rationality of the combined logarithmic spiral failure mode was verified by comparing with the existing literatures.At the same time,the influence of different parameters on the ultimate support force and the critical failure mode were discussed,and the schematic diagram of the critical sliding surface was presented.The results showed that when the internal friction angle and cohesion of the upper stratum were fixed,the ultimate support force decreased with the increase of the internal friction angle and cohesion of the lower stratum.With the increase of the diameter of the tunnel,the ultimate support force increased significantly.The depth coefficient was defined as the ratio of the depth of the upper stratum to the diameter of the tunnel.The smaller the depth coefficient was,the more sensitive the ultimate support force was to the variations of the shear strength parameters of the stratum.But for a single stratum,the change of depth coefficient has no effect on the ultimate support
作者
代仲海
胡再强
DAI Zhonghai;HU Zaiqiang(Inst.of Geotechnical Eng.,Xi’an Univ.of Technol.,Xi’an 710048,China)
出处
《工程科学与技术》
EI
CAS
CSCD
北大核心
2021年第2期95-102,共8页
Advanced Engineering Sciences
基金
陕西省自然科学基金项目(2017JM5059)。
关键词
盾构隧道
复合地层
极限上限分析法
开挖面稳定性
shield tunnel
composite strata
upper bound limit analysis method
stability of excavation face
