Study On Deformation Characteristics And Control Technology Of High Ground Stress TBM Tunnel

Based on a TBM construction tunnel project of a national key railway,this thesisr studies the construction mechanical behavior,support system optimization,sensitivity of surrounding rock deformation influencing factors and surrounding rock deformation law of high ground stress TBM tunnel,and provides theoretical basis for TBM tunnel construction and support.The main research contents and achievements are as follows:（1）Study on the mechanical behavior of TBM tunnel construction in high geostress Ⅳ surrounding rockIn the high ground stress level Ⅳ surrounding rock section,the tunnel construction of the primary support system is simulated,and the stress characteristics,surrounding rock stability,support deformation and stress characteristics are analyzed respectively.The results show that the influence range of plane stress of surrounding rock at the analysis section is about 5.37D（D is the excavation diameter of TBM tunnel）.The spatial influence range of vertical stress is mainly concentrated in the range of 2.18D in front of the tunnel face and 1.18D behind the tunnel face.The spatial influence range of horizontal stress is mainly concentrated in the range of2.45D in front of the tunnel face and 1.59D behind the tunnel face.The displacement of surrounding rock is mainly concentrated in the range of 0.91D in front of the tunnel face and 3.27D behind the tunnel face.The maximum plastic zone at the foot of the wall is 0.63D.The settlement value of the steel arch vault is 25 mm,the horizontal displacement is 6.06 mm,and the maximum axial force of the side wall on both sides is 484 MPa.The maximum principal stress inside the shotcrete side wall is65.4 MPa.The stress borne by the tunnel support structure of the primary support system exceeds its own bearing capacity,which is easy to cause large deformation of surrounding rock and damage of the support structure.（2）Optimization of TBM tunnel construction support system in high geostress Ⅳ surrounding rockThe tunnel with long and short bolts combined with multiple shotcrete combined support system can improve the stability of its support structure and surrounding rock.In order to analyze the influence of different supporting structures on the control of surrounding rock deformation in the Ⅳ grade surrounding rock section of high ground stress,the sensitivity of the factors affecting the deformation of surrounding rock is studied,and the fast calculation formula of structural optimization is obtained.Based on the regression orthogonal test design,the regression orthogonal test was carried out by using L₈（2⁷）orthogonal table,and the regression equation was established.The results show that the ground stress level plays a decisive role in the deformation of surrounding rock.The length of short anchor rod,the spacing of steel arch and the longitudinal spacing of anchor rod all have significant influence on controlling the deformation of surrounding rock.（3）Study on the deformation law of surrounding rock of TBM tunnel in high ground stress grade Ⅴ surrounding rockIn the TBM construction section of high ground stress grade Ⅴ surrounding rock,considering the interaction of long and short anchor length and the interaction of anchor ring longitudinal spacing,the L₂₇(3¹³)orthogonal table is used to design the experiment.The primary and secondary order of factors affecting the settlement of the vault is as follows:steel arch longitudinal spacing>shotcrete grade>anchor longitudinal spacing>anchor ring spacing>short anchor length>long anchor length>long and short anchor interaction>ring longitudinal spacing interaction.The primary and secondary order of the factors affecting the horizontal displacement results is:anchor longitudinal spacing>shotcrete grade>steel arch longitudinal spacing>anchor ring spacing>short anchor length>long anchor length>long and short anchor interaction>ring longitudinal spacing interaction.There is a certain interaction between the long anchor and the short anchor,but the interaction effect is not very obvious.There is no interaction between the longitudinal spacing of the anchor ring,and the influence of the two can be ignored in the design and construction.