上公山隧洞4+439部位TMB卡机地质条件及后护盾顶部塑性变形分析

Geological Conditions of TMB Jamming at 4+439 Section of Shang’gongshan Tunnel and Deformation Analysis of the Top of Back Shield

被选做长距离地下隧洞施工的岩石掘进机(TBM)以快速施工优势明显著称,当遇到软弱围岩加断层破碎带时,常发生卡机等事故,面临工期延误等挑战。穿越元古界黑山头组砂质板岩等软弱岩体的上公山隧洞,施工中多次发生围岩大变形卡机等施工地质灾害。其中较严重的是在桩号4+439侧向扩挖过程中TBM后护盾出现变形裂缝的严重事故。采用X-衍射粘土矿物分析、岩体受力模型分析和有限元数值模拟方法,研究软弱围岩与TBM相互作用下莫尔圆和库伦强度曲线的关系变化,模拟断层出露于隧洞掌子面不同部位时所产生的位移变化。结果发现,断层出露于掌子面中部时顶拱位移最大,侧向扩挖状态下护盾变为有侧向约束的单轴压缩状态,使顶部受压,反分析得到后护盾刚度系数K=153.00 kN/mm。鉴于所研究软弱围岩和小角度交切断层等不利地质条件,TBM正常适用受太多影响使工期延误,最终剩余洞段被钻爆法所取代。

Because of the obvious advantage of rapid construction,Tunnel Boring Machine(TBM)is often used for long-distance underground tunnel construction.When it comes to weak surrounding rock and fault fracture zone,it is often jammed and faced with such challenges as construction delay.During the construction of Shang’gongshanTunnel,which passes through the weak rock such as sandy slate of HeishantouFormation(Pt1hs)in Proterozoic,there are many construction geological disasters such as large deformation of surrounding rock and jamming.One of the most serious accidents is the deformation and crack of TBM back shield in the process of lateral excavation at pile 4+439.Using XRD clay mineral composition analysis,rock stress model analysis and finite element numerical simulation method,the relationship change of Mohr circle and Coulomb strength curve under the interaction of weak surrounding rock and TBM is studied,and the displacement change of fault exposed in different parts of tunnel face is simulated.The results show that when the fault is exposed in the middle of the face,the displacement of the top arch is the largest,and the shield changes into a uniaxial compression state with lateral restraint under the condition of lateral expansion excavation,which makes the top compressed.The back analysis shows that the stiffness coefficient of the back shield is k=153.00kn/mm.In view of the unfavorable geological conditions such as weak surrounding rock and small angle intersecting fault,the normal use of TBM is affected and the construction period is Seriouslydelayed,which is finally replaced by the traditional drilling and blasting method.The results of this paper are expected to provide reference for similar projects.