| With the rapid development of urban underground rail transportation,single-line subway transportation can no longer meet the needs of urban transportation.The subway lines must be crossed into a network and interchanged to meet people’s various travel requirements.Therefore,underpass projects are becoming more common in urban transit construction.If the construction method of the new subway is not selected properly or the deformation of the existing line is not well controlled in the underpass project,the deformation of the existing line above may exceed the control requirements,thus affecting the safety of the existing line and the safe operation of the existing subway.In the light of the new Beijing Metro Line 16 National Library～Erligou station underpass the existing Line 4 National Library～Dongwuyuan station and Line 9National Library～Baishiqiaonan station,the deformation law of different types of existing subway lines is analyzed by means of theoretical analysis,refine numerical simulation and field monitoring.Meantime,based on the existing tunnels safety and operation comfort,the existing structural deformation control standards were formulated.Finally,the filed results of engineering are used to verify the conclusions above.The main work and results are as follows:(1)A spatial coupling model of the tunnel,track bed,and rail was established,and the deformation transfer laws of those under different conditions were analyzed.The results show that when the width of the existing line settlement groove is large,the track bed structure and the tunnel follow well,and there is no separation between the layers.On the contrary,when the width of the settlement groove is small,The local deformation between those is quite different,and there may be gaps between the layers.(2)Considering the operation comfort of existing subway,the peak vertical acceleration 1.30m/s~2 of the subway was selected as the comfort control index and the existing structural settlement control standards to meet the train operation comfort under different deformation modes were respectively formulated.The results show that the settlement control value is approximately proportional to the peak acceleration of the train body.Within the vertical acceleration peak standard limit,the settlement control value range increased from 37 to 86mm when the width coefficient of the settlement groove i increased from 2 to 10m.(3)Considering the tensile strength of the existing tunnel structure,the relationship between different deformation indexes and structural safety are analyzed.The results show that settlement is the most intuitive,accurate,and easiest deformation indicator for judging whether an existing structure is safe.Structural settlement should be used as the main control indicator in the project.Meantime,considering the normal use limit state of the existing tunnel and the safety of the existing track,the settlement control value calculated that satisfies the structure safety is 16.1mm.(4)The finite element analysis model of the engineer is established to analyze the deformation law of the existing tunnels.Due to the different structures of the existing three lines,the settlement peaks are also different.The results show that the settlement peak of the shield of Line 4 is the largest,the mining method of Line 4 is the second,and the deformation control effect of the double arched of Line 9 is the best.(5)According to the comparative analysis of the existing three-line numerical calculation and the filed monitoring,the deviation value of them is basically within a reasonable range of 20%from the perspective of the vertical deformation trend.The filed results agree well with the numerical simulation results.Both these two results meet the formulated deformation control standards that take into account structural safety and subway operation comfort.The existing three-line is in a safe and comfortable state. |
PDF Full Text Request