Study On The Interaction Mechanism Between Double Shield TBM Tunneling And Surrounding Rocks In Duoxiongla Mountain Of Tibet

At present,China is building large-scale traffic and water conservancy deep tunnels,especially in Tibet,where water resources are abundant and geological conditions are complex.Its construction safety has restricted the safety and progress of major national infrastructure.Compared with traditional drilling and blasting methods,TBM construction method has high efficiency,good construction quality,and construction process is conducive to environmental protection.Therefore,TBM construction method is the preferred construction method for many major lifeline construction projects.It is of great significance to study the mechanism of interaction between TBM and surrounding rock.This paper makes a deep study on the mechanism of TBM excavation and surrounding rock tunneling in Duoxiongla tunnel in Tibet from four aspects: field test,rock physical and mechanical test,indoor model test and numerical simulation analysis.(1)Through site investigation and testing,this paper analyzes the geological conditions of the tunnel area,the conditions of groundwater and surrounding rock,and lays a foundation for exploring the situation of the double shield TBM excavation;it analyzes the double shield TBM shield friction resistance and tunnel surrounding rock.Deformation,the influencing factors affecting the TBM excavation with double shields in the Duoxiongla Tunnel in Tibet were obtained.(2)The physical and mechanical tests of the rock were carried out by sampling at the site of the Duoxiongla tunnel in Tibet.The physical and mechanical properties of the rock under triaxial loading and triaxial loading and unloading were tested to simulate the actual rock state of the excavated tunnel and the influence of excavation unloading on the surrounding rock.The physical and mechanical parameters of the surrounding rock were obtained.And so on,laid the foundation for subsequent model tests and numerical simulations.(3)There is a gravel-packed layer between the surrounding rock and the segment of the tunnel.To explore the influence of the gravel-packed layer on the surrounding rock and segments of the tunnel,an in-house model test was conducted based on the actual excavation process of the Duoxiongla tunnel in Tibet.The ratio of wall rock model was calculated theoretically,and the cutterhead was used to tunnel tunneling.After the tunneling was completed,the segments were installed and backfilled with bean gravel.The function of the gravel pack in the TBM tunneling process was obtained and analyzed.(4)The finite-difference software FLAC3 D was used to establish the segment-bean gravel packing-surrounding rock model to analyze the effect of bean-gravel-filled layer on the tunnel segment and surrounding rock;to establish the TBM shield-enclosure model and analyze the TBM affecting the excavation efficiency.The friction resistance of the shield verified the rationality of the theoretical calculation.