Effect Of Deformation Of The Subgrade By Excavation Near The Existing And Analysis Of The Support Effect

With the gradually improvement of road and rail network, new lines and existing lines will inevitably form a across. The pit excavation in the across of existing bridge instruction can lead to the existing subgrade deformation and instability, then the driving safety will be effected.On the background of the bridge pier cap excavation in the across-construction of Jinqin grad bridge, established dynamic and static load numerical analysis models by FLAC3D. This article analyzed the different influence of subgrade deformation and studied different parameters’influence to existing road’s deformation supports before and after, such as distance, angle and depth,based on the Mohr-Coulomb yield criterion. The main works in this thesis as follows:(1) By consulting literature, understand the characteristics of surrounding structures deformation caused by excavation and review main deformation caused by excavation and calculating method of surface subsidence.(2) Combined with model of the single track railway roadbed filling2m height, analysised with the finite difference numerical method. The train load equivalent to the static load, analysis parameter changes affect excavation of existing subgrade deformation whether supporting or not in the homogeneous soil excavation. Obtained critical distance, depth and angle when no supporting. And analysis supporting effect in the different excavation distance, angle and depth of excavation.(3) The train load to the exciting force function act on the model. Make numerical simulation of existing subgrade excavation, analysis existing subgrade deformation affected by parameters of excavation when supporting. And static and dynamic simulation results are compared. The results show that subgrade deformation influence regularity affected by excavation parameters of two simulation ways are consistent. Subgrade settlement is mainly determined by action mode and load range. There is no effect between roadbed horizontal displacement and load mode. It mainly affected by the excavation of foundation pit.(4) According to the basic principle of circular slip surface method, the pit excavation stability under different parameters and critical conditions were anylsyzed and the coefficients of stability before and afer the pit excavation’s supports under various working conditions were getted.