| With the development of urban subway construction,the influence of shield tunnel construction on the existing pipeline is inevitable,and the frequency of similar situations will increase greatly.Because the weathered sandstone is widely distributed and its property is special.Therefore,in-depth analysis of the influence of weathered sandstone shield tunneling on the existing pipeline and discussion and analysis of pipeline stress and deformation under different states can provide a basis for subsequent practical engineering design and decision.According to the different mechanical properties of underground pipelines,the deformation mechanism of surrounding rock caused by tunnel excavation was discussed and analyzed based on Peck formula.Combined with beam model of elastic foundation,the rigid pipe deformation caused by double-wire shield excavation is calculated and deduced theoretically,and the calculation formula of pipeline deformation in the process of double-wire shield tunneling is obtained.Based on the actual engineering data of shield section from International Town to Aviation Industrial Park Station of Hefei Rail Transit Line S1,the corresponding model is established by using FLAC3 D simulation software.According to the previous survey data and relevant specifications,the simulation process of soil pressure balance shield tunneling process is introduced,and the relevant parameters of shield tunneling are calculated.The initial stress field of the established model soil is generated.Because the weathered sandstone is loose,the initial settlement is large,and the settlement decreases gradually along both sides of the model,showing a symmetrical distribution.By setting different working conditions,the pipeline deformation and force in the process of double-line shield tunneling were analyzed,and the following conclusions were obtained:1.The vertical displacement of surrounding rock caused by shield tunneling in weathered sandstone is mainly uplift displacement,and the surface displacement on both sides of the section of single-line through backing structure is the largest,and tends to be gentle after double-line through.2.Under various working conditions,the vertical displacement of pipeline located in weathered sandstone always shows a trend of increasing gradually with shield excavation.The effect of double shield tunneling on pipeline displacement in weathered sandstone is more similar to the result of vector superposition.3.When pipelines with different buried depths are parallel to the tunneling direction of shield,the vertical displacement of pipelines tends to increase along the tunneling direction of shield,that is,the maximum displacement occurs in the exit section of shield.The vertical displacement decreases after the shield tunneling.The stress value of the pipeline increases after the two lines are connected.The longitudinal tensile stress is mainly borne by the pipeline in the outlet section,and the pipeline with deeper burial depth is more vulnerable to damage.4.The maximum change of vertical displacement occurs in the secondary disturbance of weathered sandstone caused by rear shield tunneling.Due to the secondary disturbance caused by double-line excavation,the displacement and stress of the pipeline on the right side(the leading side of the shield)are greater than those on the left side.5.In the process of tunneling the weathered sandstone double-wire shield through the existing pipeline,the vertical displacement of the pipeline is not greatly affected by the pipeline depth;Pipelines mainly bear circumferential tensile stress and longitudinal tensile stress.The longitudinal tensile stress of pipelines with shallower depth is larger in the process of tunneling.Figure [63] table [11] reference [65]... |
