| In tunnel and underground structure engineering,The double-shield TBM technology has gradually become the optimal choice for deep-buried and long water conveyance tunnel(diameter less than 8m).However,with the construction of projects with complex geological conditions,such as water diversion from central Yunnan,Hanjiang to Weihe River,and water resources allocation in the Pearl River Delta,it is increasingly necessary to make scientific and technological breakthroughs and innovations under the double-shield TBM tunneling mode.Therefore,this paper takes the Liupanshan ZQ1# water delivery tunnel of the Bailong River water diversion project as the engineering background,which is based on the rock mass elastoplastic theory and considers installation of concrete pipe fragments for the double-shield TBM tunneling of the ZQ1# water delivery tunnel,and uses the MIDAS GTS NX geotechnical and tunnel structure analysis software to study the stability of the surrounding rock and the mechanical characteristics of the segment lining structure of the tunnel,and analyses the influence of the change of the physical and mechanical parameters of the V type surrounding rock on the displacement and stress of the surrounding rock and the displacement and stress of the segment lining structure.It is expected to provide some reference for the actual design and construction of Liupanshan tunnel of Bailong River Project.During the research process,the main work and conclusions are as follows:(1)Under the action of high ground stress,the following conclusions can be drawn by comparing the results of the two working conditions of "segment" support system and "bolt +segment" support system: In the tectonic stress field,the displacement of the vault and the bottom varies greatly after the excavation and unloading of the tunnel,and the horizontal deformation of the tunnel is also great because the horizontal pressure of the surrounding rock is greater than the vertical pressure of the surrounding rock.Stress concentration occurs mainly at the top and bottom of the tunnel,and the compressive stress at the waist of the tunnel arch is large.In the whole of surrounding rock-grouting layer-segment,the grouting layer is mainly used as the force transmission part between the segment and the surrounding rock.After bolt support is applied,the deformation range of surrounding rock at the arch waist decreases obviously,which indicates that it can significantly improve the stability of soft rock section,and make the displacement change of surrounding rock at all parts around the tunnel relatively uniform.The anchor rod component can effectively reduce the stress of the tube segment and make it meet the design requirements.(2)The stress field data of the engineering area is analyzed,and the initial stress field formula of the Liupanshan water conveyance tunnel section is obtained,and it is used in the simulation of the double-shield TBM tunnel face propulsion.The vertical displacement of surrounding rock and the maximum principal stress of surrounding rock are analyzed,and the stress characteristics of the segment lining structure are studied.The results show that the roof begins to deform when the palmface reaches 0.5 times the diameter of the tunnel before the monitoring fault.When the tunnel diameter reaches 0.5 times after the monitoring section,the roof settlement increases greatly.When the tunnel diameter is 2 times behind the monitoring section,the roof of the tunnel no longer changes greatly.When advancing to the last 4 times of the diameter of the tunnel,displacement and settlement no longer occur,and the monitoring section remains basically stable.The law of maximum principal stress change of surrounding rock is basically consistent with the law of vertical displacement;the Mises equivalent stress of segment lining structure tends to be stable when it is twice the hole diameter from the tunnel face,and the maximum stress value does not exceed the requirements of the design scheme.(3)By selecting typical parameters and their variation intervals,a sensitivity analysis of the physical and mechanical parameters of the surrounding rock was carried out,and the following conclusions were drawn: For the displacement of surrounding rock,elastic modulus,internal friction Angle and Poisson’s ratio are highly sensitive parameters.The elastic modulus,internal friction Angle,Poisson’s ratio and cohesion are all low sensitive parameters for the stress change of surrounding rock.For the change of tube displacement and stress,the elastic modulus and internal friction angle are highly sensitive parameters,while the cohesion and internal friction angle are low sensitive parameters. |
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