Deformation Control of Crossing Over Existing Bridge by Shallow Tunneling

When shallow tunnels crosses through existing bridges, there will be unfavourable influence on adjacent bridge pile, and even more serious safety risk for exsiting bridges during operating.So, to control this unfavored deformation, necessary techniques must be adopted in order to keep the existing bridge safe during construction.In this paper, by taking Yong He Gong station to He Ping Li North Street station interval of line 5 in Beijing for example, deformation control method of crossing over existing bridge by shallow tunneling is presented.Firstly, combinating numerical modelling with project experiences before tunneling, the stage and total control criterion of bridge pile deformation are detemained.Secondly, according to monitoring test of main monitoring section in bridge areas, soil deformation rule in this area are obtained. At the same time, grouting test is adopted to determine suitable grouting material and parameters which supply evidence for optimizing methods.Finally, based on the stage control criterions, dynamic control is adopted for main construction steps to realize total control target during tunnelling.The measured data shows that actual differential settlement of bridge is up to 58.4%of control standard, meets the control requirement and makes existing bridge safe.Successful application of this control method can provide important reference for similar projects.