Study On Seismic Behavior Of Railway Bridge Pier In Digging Well Foundation With Roots

Digging well foundation has been widely used in railway bridge in northwest China because of its simple construction and low cost.The existing earthquake damage shows that the damage of the foundation pier under the earthquake is mainly caused by the foundation uplift and deflection because of the failure of the soil around the foundation,which can may let the pier lose the bearing capacity prematurely.(1)Through the investigation of relevant literature,the development and status quo of seismic research on railway bridge foundation at home and abroad are sorted out from the aspects of seismic damage characteristics,seismic performance of the foundation and calculation model.Based on the analysis of seismic damage phenomenon and research status of ordinary digging well foundation,a new root digging well foundation is proposed to improve the seismic performance of ordinary digging well foundation.(2)Based on the railway digging well foundation pier,the scale model of the root shaft foundation pier is designed and made according to the similarity ratio of 1:8.The damage characteristics,hysteresis characteristic,skeleton curve,bearing capacity and energy consumption capacity of foundation pier-soil are studied by quasi static test.The results show that the root bond improves the seismic performance of the dug well foundation significantly,and its bearing capacity can reach 36%.The failure characteristics,skeleton curve,bearing capacity,hysteretic characteristics,energy consumption capacity and degradation of stiffnessare of the railway pier,which is supported by root digging well foundation,under horizontal reciprocating loadare studied by pseudo-static test.(3)Based on ABAQUS finite element software,the static nonlinear finite element model of railway root digging well foundation pier is established,and its seismic performance under horizontal reciprocating load is carried out,and the analysis results and model test results are checked.The results show that the model can analyze the seismic performance of this foundation.(4)Based on the finite element analysis model,the seismic performance of the root bond length,width and root bond arrangement are studied.The results show that increasing the length of the root bond and increasing the width of the root bond when the horizontal spacing of the adjacent root bond is unchanged can both improve the bearing capacity of the root digging well foundation pier.Increasing the same number of root bonds at the bottom of the digging well foundation is better to improve the bearing capacity of the root digging well foundation pier than increasing at the sides of the digging well foundation.(5)Based on the finite element analysis model,the seismic performance of the root digging well foundation pier in the seasonal frozen soil area is studied,and the influence of the frozen soil thickness and the melt soil thickness on the seismic performance of the foundation pier is compared.The results show that with the increase of the frozen soil thickness,the bottom of the foundation pier will be destroyed,but the horizontal bearing capacity of the foundation pier is improved,while the melting of the seasonal frozen soil will reduce the bearing capacity of the foundation pier.