Study On Mechanical Behavior Induced By Undercrossing Construction To Existing Metro Tunnel

With the large-scale construction of city track traffic and rapid development of Metrolines in operation, the engineering cases that subway tunnel under construction by the newsubway lines or similar underground structure are growing with each passing day, how torationally and effectively protect the subway tunnel structure safety, ensure the normaloperation of subway, has become the city track traffic safety protection structure of a pressingmatter of the moment. How to effectively forecast and analyse the influence degree of underconstruction to metro tunnel, to take targeted measures to control the influence of underconstruction in a safe range, is the main technical bottleneck of the current undercrossingexisting subway tunnel engineering. Therefore, based on the undercrossing existing subwaytunnel construction effect, establish the corresponding mechanical model, and apply thismodel to systematically researched the typical subway tunnel structure mechanical behavior.The specific work is as follows：（1）Take the thought of common load-structure method as lessons, simplify the subwaytunnel structure beneath stratum as a ground spring, above the tunnel and two side formationis simplified to pressure load, apply the incremental calculation method, establish load-structure-mechanical model for calculation of coefficient of subgrade reaction reductionmethod which can consider the influence of the under construction. Combining the underpassconstruction process, getting through continuous reduction tunnel beneath the coefficient ofsubgrade reaction coefficient of subgrade reaction range and size, we can have a dynamicprediction analysis of underpass construction influence on Metro tunnel.（2）Apply the established load–structure-coefficient of subgrade reaction reductionmethod, aim at shield tunnel, composite supporting tunnel and the excavation andcast-in-place box type structure of three kinds of typical subway tunnel structure, we have asystematical analysis of mechanical behaviors from the buried depth of tunnel, crossing underthe influence scope and the reduction degree of influence factors on crossing under theexisting subway tunnel structure.（3）Take a shield tunnel undercrossing composite supporting tunnel project as anexample, use the establishment of load–structure-coefficient of subgrade reaction reductionmethod for calculation of coefficient of subgrade reaction reduction method, analyse theshielding under construction on existing metro tunnel subsidence influence, and with a tunnelsubsidence observation data and the stratum structure method of3D finite element calculation results were comparative analysed.（4）In order to further explore the measures which can effectively reduce the shieldingunder construction impact on existing tunnel engineering，we take shield tunnel undercrossingcomposite supporting tunnel project as an example, use the stratum structure method of3Dfinite element model, study the effect on shielding under construction to existing metrotunnel，and adopt the related parameter sensitivity analysis，at last we gain some feasiblemeasures.