Deformation Law Research On New Tunnel Crossing Existing Metro Structure In Beijing

With the increase of Beijing metro lines,a spate of newly-built tunnel crossing the existing metro structure engineering emerge.Due to the strict requirements of existing metro safety operation,that result in an increase of the difficulty in construction,construction period,and the economic cost.Knowing about the deformation regular of the new tunnel crossing existing metro structure engineering,and looking for a quick and reliable prediction method,which become an urgent problem in urban construction.In this paper,based on the eight crossing engineering which are built in the Beijing area,such as new tunnel crossing the metro line 1、6.Using means of correlation analysis、normality test、Gaussian fitting、numerical simulation,study the deformation patterns and prediction methods of new tunnel crossing metro structure engineering are studied.The following main achievements were achieved.(1)With analyzing the measured data,the deformation of existing metro structure during the whole construction period is divided in six stages.Which are pre-deformation fluctuating stage、deformation development stage、rapid deformation stage、later deformation fluctuating stage、slow settlement stage、stable stage.The rapid deformation stage is the stage of the most deformation of the metro structure.The cumulative deformation of the stage in lower crossing engineering accounted for 63%一70%of the maximum deformation,The cumulative deformation of the stage in upper crossing engineering accounted for 82%～88%of the maximum deformation.(2)the influence factors of deformation is studied with correlation analysis method.The deformation of existing metro structure has positive correlation with the excavation area of newly tunnel,which has negative correlation with crossing distance,crossing angular and reinforcement measures,which is correlation with the deformation the depth of embedment of newly-built tunnel and built structure of metro,and it changes with different crossing type.By analyzing the influence coefficient,the influence degree of all factors to the deformation of existing metro structure in small to lager order is crossing distance,excavation area of newly built metro,newly-built tunnel,embedment depth of existing metro structure,reinforcement measures,crossing angular.in lower crossing engineering,the influence coefficient is-0.559,0.524、-0.507,0.481,-0.44,-0.353,respectively;in upper crossing engineering,the influence coefficient is-0.887,0.67,0.586,-0.513,-0.505,-0.395.(3)The deformation of existing metro structure obey normal distribution with normality test method,the result shows,the whole deformation of existing metro structure has flexible characteristic,which is similar with deformation characteristic of natural stratum,but the deformation degree is smaller than that of natural stratum.(4)With Gaussian fitting method,combining with Peck formula,the maximum prediction equation of deformation is deduced.When in an area with lager numbers of engineering experience,and accurately estimating the parameter values of the equation,the accuracy of prediction is higher.And the correctness of the equation is verified by actual engineering and numerical simulation.