基于离散元的有砟道床防震加固措施研究

Study on anti-seismic reinforcement measures for ballasted bed based on discrete elements

地震对轨道结构构成了巨大而不可避免的威胁,因此需要采取创新的方法来减轻地震对有砟道床的不利影响。提出一种在道床表面铺设土工格栅网,在道床底部0.5 m厚度范围内添加道砟胶的加固方法,该方法可以有效改善轨道系统的抗震性能,减小地震造成的损害。首先,基于离散元法建立有砟轨道模型,可计算获得道床的横向阻力和垂向刚度,并与现场试验结果对比,验证所构建道床离散元模型的准确性。其次,在准确的模型基础上实施加固措施,通过给道床表面添加粒径相同的球体颗粒来模拟土工格栅,同时将道床底部0.5 m范围内的道砟颗粒黏结模型修改为平行黏结模型,据此构建道床加固后的离散元模型。详细对比加固前后道床的力学性能。结果表明:提出的加固措施显著提高了道床的垂向刚度,使得道床在地震时更能够抵抗竖向振动力,虽然对道床横向阻力的提升较少,但这一结果仍具有积极意义,尤其在地震冲击下;加固后的道床在横向和纵向位移以及应力方面都有明显改善,降低了道砟颗粒粉化的可能性,提高了道床的整体稳定性;道砟胶的黏结作用减小了底部道砟的竖向位移和竖向速度,有助于减小地震引起的损害。研究为减小地震对有砟道床的不利影响提供了有力的科学依据,加固措施在提高道床的抗震性能方面有较好的效果。

Earthquakes pose a great and unavoidable threat to track structures,so innovative methods are needed to mitigate the adverse effects of earthquakes on ballasted roadbeds.This paper proposed a reinforcement method of laying geogrid mesh on the surface of the roadbed and adding ballast glue within 0.5 m thickness at the bottom of the roadbed,which can improve the seismic performance of the track system and reduce the damage caused by earthquakes.First,the ballasted track model was established based on the discrete element method,which can be calculated to obtain the roadbed’s transverse resistance and vertical stiffness,and compared with the field test results,which verifies the accuracy of the constructed discrete element model.Second,based on the accurate model,reinforcement measures were implemented:(1)geogrids were simulated by adding spherical particles with the same particle size to the surface of the roadbed,and(2)the ballast particles within 0.5 m of the bottom of the roadbed were modified into a parallel adhesion model,according to which the discrete meta-model of the roadbed was constructed after reinforcement.Detailed comparison of the mechanical properties of the roadbed before and after reinforcement shows that the proposed reinforcement measures significantly improve the vertical stiffness of the roadbed,which makes the roadbed more capable of resisting the vertical vibration force during earthquakes.Although the enhancement of the transverse resistance of the roadbed is relatively small,this result is still of positive significance,especially under the impact of earthquakes.The reinforcement of the roadbed shows improvement in the transverse and longitudinal displacement responses as well as the stress responses,which decreases the possibility of ballast particle pulverization and increases the ballast particle size.The possibility of particle pulverization is reduced and the overall stability of the roadbed is improved.The bonding effect of the ballast glue reduces the vertical displacement and vertical velocity,which helps to minimize the earthquake-induced damage.The research in this paper provides a strong scientific basis for reducing the adverse effects of earthquakes on ballasted roadbeds,and the reinforcement measures have a better impact in improving the seismic performance of roadbeds.