Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safe...Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safety of the trains.Due to their good mechanical properties,twocomponent polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping.To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping,we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios,to determine an optimal composition ratio of the raw materials.Then,we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio.The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area,coordinating the dynamic response between the track structure and the subgrade bed.Thus,the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.展开更多
Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was est...Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was established to analyze the dynamic responses of a ballastless track,and results showed that the concrete base and roadbed were detached because of the whipping effect arising from the rainwater intrusion channel.An in-situ soil core test showed that the intruded rainwater accumulated in roadbed to form standing water and saturated the roadbed.The flapping action of the concrete base caused by the whipping effect led to mud formation mixed with fine particles and rainwater,which migrated upward under the pore-water pressure(PWP)gradient.Mud pumping resulted from continuous particle migration in the saturated roadbed under moving train loads:under normal roadbed condition,coarse and fine particles were uniformly distributed in the roadbed;in early period of mud pumping,fine particles migrated downward to bottom of the roadbed because of the rainwater infiltration flow;in middle stage of mud pumping,fine particles migrated upward and gathered at the roadbed surface under PWP gradient;in later period of mud pumping,fine particles were entrained and removed with the dissipation of excess PWP.Moreover,a full-scale physical model was established to reproduce mud pumping,and polyurethane injection remediation against mud pumping was validated on this physical model.The remediation method was applied to an in-situ mud pumping.The deviation of the vertical track profile reduced remarkably and remained at a low level within half a year,showing a good long-term service performance of the polyurethane remediated roadbed.展开更多
基金The authors gratefully acknowledge the financial support for this research by the National Natural Science Foundation of China(Grant Nos.51978588 and 52078434)。
文摘Mud pumping in subgrade beds under ballastless tracks will deteriorate the dynamic performance of infrastructure under railway lines,reduce the smoothness of the railway lines,and seriously affect the comfort and safety of the trains.Due to their good mechanical properties,twocomponent polyurethane materials can be used for grouting to treat the fouling problems caused by ballastless track mud pumping.To develop a polyurethane formula suitable for the treatment of ballastless track mud pumping,we first performed indoor experiments to investigate the mechanical properties and gelation time of polyurethane elastomers synthesized with different raw material composition ratios,to determine an optimal composition ratio of the raw materials.Then,we conducted a dynamic field test to verify the remediation effect of the polyurethane material fabricated according to the design ratio.The results showed that polyurethane grouting material with the selected design ratios improved the contact characteristics between the surface layer of the subgrade bed and the base plate in the area,coordinating the dynamic response between the track structure and the subgrade bed.Thus,the obtained polyurethane grouting material could be used to renovate mud pumping areas of ballastless tracks with a good treatment effect.
基金This article was supported by the National Natural Science Foundation of China(No.52125803,No.51988101,and No.52008369)the National Key Research and Development Program(No.2018YFE0207100).
文摘Mud pumping induced by moving train loads on rainwater-intruded roadbed causes intensive track vibrations and threatens safety of high-speed trains.In this paper,a vehicle–track–subgrade finite element model was established to analyze the dynamic responses of a ballastless track,and results showed that the concrete base and roadbed were detached because of the whipping effect arising from the rainwater intrusion channel.An in-situ soil core test showed that the intruded rainwater accumulated in roadbed to form standing water and saturated the roadbed.The flapping action of the concrete base caused by the whipping effect led to mud formation mixed with fine particles and rainwater,which migrated upward under the pore-water pressure(PWP)gradient.Mud pumping resulted from continuous particle migration in the saturated roadbed under moving train loads:under normal roadbed condition,coarse and fine particles were uniformly distributed in the roadbed;in early period of mud pumping,fine particles migrated downward to bottom of the roadbed because of the rainwater infiltration flow;in middle stage of mud pumping,fine particles migrated upward and gathered at the roadbed surface under PWP gradient;in later period of mud pumping,fine particles were entrained and removed with the dissipation of excess PWP.Moreover,a full-scale physical model was established to reproduce mud pumping,and polyurethane injection remediation against mud pumping was validated on this physical model.The remediation method was applied to an in-situ mud pumping.The deviation of the vertical track profile reduced remarkably and remained at a low level within half a year,showing a good long-term service performance of the polyurethane remediated roadbed.
