Analysis In Influences On Railway Structure Caused By Metro Tunnel Undergoing Through Existing Lines

The metro engineering is developing with the growth of the population, and more andmore metro tunnels go through existing lines. Construction of shallow tunnel causes soildisturbances, and will affect initial stress state of surrounding and upper soil. Due to thecomplexity and uncertainty of construction technology, construction quality, surroundingsand soil, surface deformation troubles of varying degrees will appear. The underpasses of newtunnels are of high risk, involving normal operation of existing railways and constructionsafety of new tunnels. The number of high-speed trains is bigger and bigger with the speedincrease, raising the level of quality requirement of line, extremely controls over rail structuraldeformation. In a word, it is necessary to find a rational and effective way to minimize effectof tunnel structure to surface and other structures.Based on the theory of strata loss, pore pressure and consolidation, and secondaryconsolidation settlement, this paper analyzed causes of ground movement and deformationcaused by tunnel structure, the development law and characteristics of time effect and spatialeffect of ground movement, and summarized influences of tunnel structure on embankmentsand lines.First, according to the monitoring data of undercrossing metro tunnels, the authorresearched influence of two-tube tunnels on existing lines, analyzed the maximum settlementpoint, transverse distribution characteristics of settling tank. And then chosen key tunnel axisand the very middle point of two tunnels to analyzed variation characteristics of measuringpoints’ settlements and differential settlements of tunnels, and relationship between embanksettlement and crown settlement.Second, on the basis of geological conditions and construction of undercrossing metrotunnels, the author set up a numerical model to research embankment settlement value ofdifferent conditions, such as with or without train loads, variations of soil modules、Poissonratios、internal friction angles、cohesions and tunnel space, summarized key factors affectground settlement value, and verified the module is correct according to comparativelyanalyzed with measured data.Last, on the premise of ride comfort, Under the guidance of maintenance and adjustmentof operated lines, taking track deformation characteristics the reference, the author proposedcontrol criterion of undercrossing tunnel construction and measures for control deformation ofembankment and tunnel, to reduce ground deformation caused by tunnel construction, with administration rules of rail safe operation as the principle and online measured data andnumerical simulation the basis.