Dynamic Response Analysis of Box Subgrade of High-Speed Railways
In order to study the dynamic response of the box-type subgrade of high-speed railway under train load,the three-dimensional finite element model of track-subgrade-foundation is established by numerical simulation method,and the distribution law of dynamic stress,dynamic displacement and acceleration of the box-type subgrade is analyzed,and compared with the conventional fill subgrade.The results show that the dynamic response time history curve under train load changes periodically,and the superposition effect of two adjacent bogies in different carriages decreases with the increase of depth,and the occurrence time lag is about 0.1 s.The dynamic response is distributed along the depth and tends to decrease.In the box-type subgrade,the vertical dynamic stress and acceleration attenuation rate can reach more than 60%and 75%respectively.The dynamic response is distributed along the transverse distribution,and the lateral distribution difference is small within the range of the supporting layer,and the maximum difference of vertical dynamic displacement of the roof plate is only 0.008 mm,while the change is rapid outside the range.The dynamic response is distributed laterally,mainly in the shape of"saddle"and"U",and peaks occur below the edge of the supporting layer,at the connection between the vertical plate and the top and bottom plate,and at the edge of the bottom plate,and there is a stress concentration effect.The maximum dynamic stress on the subgrade surface is 39.6 kPa,the maximum dynamic displacement is 0.165 mm,and the maximum dynamic stress in the subgrade is 100.6 kPa,and all meet the design requirements.Compared with the conventional fill subgrade,the attenuation rate of vertical dynamic stress of box-type subgrade is larger up to 95%,and the acceleration is small,and the absorption and dissipation effect on dynamic load is more significant.The vertical dynamic displacement amplitudes of box-type subgrade and conventional subgrade surface are 0.165 mm and 0.329 mm and the maximum difference is 0.036 mm and 0.189 mm respectively.The box-type subgrade has smaller dynamic displacement,more uniform lateral distribution and better integrity.
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