Analysis Of Mechanical Properties Of Polyurethane Foam Ballast Bed Based On Discrete Element

Ballasted bed is widely used in passenger and freight co-located railways,heavy-load railways and some special sections of high-speed railways due to its advantages of low construction cost and easy maintenance.The dense passenger and freight transportation have put forward higher requirements for ballasted bed.The reciprocating effect of the train load is very detrimental to the cumulative deformation and service state of the ballast bed.It also increases the number and cost of daily maintenance and repair of the railway.Based on this railway system proposed the new polyurethane foam bed structure.But its application in China is still in the early stage of exploration,and theoretical research has not been systematically carried out.Based on this situation,the PFC discrete element software is used to establish a discrete element model of polyurethane foamed ballast bed in this paper,which realizes the coupling of rigid and flexible media in the discrete element model,and analyzes the mechanical characteristics of polyurethane foamed ballast bed.main tasks as follows:(1)Using PFC's own program and self-programming language,a modeling method for multi-medium filling structure in discrete elements is proposed.In view of the coexistence and discontinuous characteristics of polyurethane foam structure with multimedium,the particle cluster unit in the discrete element model is used to simulate rigid ballast particles,and the small ball unit is used to simulate flexible polyurethane foam.This method can take the volume of polyurethane foam into account.The coupling of rigid-flexible media in discrete elements was realized for the first time,and the correctness of the model was verified by combining field test data.(2)The static and dynamic characteristics of the polyurethane foamed ballast bed are calculated and analyzed.By comparing the mechanical indexes such as the displacement of the sleeper,the stiffness of the ballast bed,the cumulative deformation of the ballast bed,and the contact force of the ballast bed,the polyurethane foamed ballast bed is analyzed.The advantages and disadvantages of the ballast bed is analyzed,and choose the best curing mode.(3)Analyze the influence of external conditions on the mechanical properties of polyurethane foamed ballast bed.Considering the external conditions of different vehicle axle loads,different driving speeds,casting section shape and ballast dirt,analyze the sleeper displacement of polyurethane foamed ballast bed under the above conditions,the cumulative deformation of the ballast bed,the contact force of the ballast bed and other mechanical characteristics.And scientific and reasonable design,construction and maintenance suggestions is gived.