Dynamic Response And Cumulative Deformation Prediction Of High-speed Railway Pile-supported Geogrid-reinforced Embankment

During the construction of high-speed railway,it is inevitable to encounter soft soil foundation with weak bearing capacity and prone to cumulative deformation.How to effectively control the post construction settlement of high-speed railway subgrade has become one of the core technical problems of high-speed railway construction.Geogrid-reinforced pilesupported embankment has the characteristics of convenient construction,small settlement and high stability.It has been widely used in highway and railway construction at home and abroad.This paper uses technical means of combining theoretical analysis and numerical simulation to research the dynamic response and cumulative deformation prediction of geogrid-reinforced pile-supported embankment of high-speed railway.The main research contents are as follows:(1)The load transfer mechanism of geogrid-reinforced pile-supported embankment is explored and the calculation methods of soil arching effect and tension membrane effect are summarized.Different calculation methods of soil arching effect are based on different soil arching models,the calculation models of tension membrane effect are mostly in twodimensional level;Based on the existing soil arching model,the calculation formula of pile-soil stress ratio is deduced from soil arching effect and tension membrane effect.Finally,the calculation results are reasonable by compared with the measured results in the references.(2)Based on the finite element analysis software MIDAS-GTS NX,the three-dimensional numerical model of geogrid-reinforced pile supported embankment is constructed according to code for design of high-speed railway and engineering examples,and the track components are simplified.The moving uniform load is used to replace the fixed concentrated force load,and the ground curved spring is set to simulate the absorption of reflected stress wave by the foundation.According to the calculation results,the variation law of dynamic stress with time and spatial distribution characteristics are explored,and the variation law of soil element stress path in embankment under high-speed railway load is further studied;The influence of subgrade elastic modulus,train axle load and speed on dynamic stress is analyzed.Finally,the calculation method of dynamic stress at different depths in geogrid-reinforced pile-supported embankment and the control standard of subgrade thickness are explored.(3)Several commonly used empirical models of soil cumulative deformation are briefly introduced.According to the existing results to verify the modified exponential model,The results show that the calculation results of the modified exponential model are close to the measured results;Combined with the calculation results of dynamic deviator stress of the numerical model,the modified exponential model is used to predict the cumulative deformation of geogrid-reinforced pile-supported geogrid-reinforced embankment of high-speed railway under long-term high-speed railway load.