| With the rapid development of China’s social economy,the population flow has greatly accelerated,and the demand for the level of traffic in and between cities is increasing day by day.The planning of land for traffic on the ground is becoming increasingly tense,and cities are trying to plan to combine property and subway.When the train is running,it will inevitably have a vibration and noise impact on the upper building and the surrounding environment.The existing slab track has a CA mortar(Cement Asphalt Mortar)adj ustment layer,which is mainly used to support the track plate and adjust the track construction error,and can provide certain elasticity and vibration isolation.Therefore,it is of practical significance to improve the damping performance of CA mortar a nd improve the damping effect of track.In this paper,the effects of mica powder(MP),hollow glass bead(HGB)and rubber powder(RP)on the working properties,mechanical properties and damping properties of CA mortar,and the influence of modified CA mortar on the dynamic response of track structure and its damping effect are studied.The details are as follows:The ratio and mechanical properties of modified CA mortar were studied.The basic properties of modified CA mortar were studied by mixing different amount of mica powder,hollow glass bead and rubber powder respectively.The flowability,extensibility and mechanical properties of modifi ed CA mortar were tested,and the effect of temperature on compressive strength of CA mortar was investigated.The results show that the three additives increase the mobility of CA mortar and decrease the spreading degree of CA mortar.Addition of mica powder and hollow glass beads increase the flexural strength,compressive strength and elastic modulus of CA mortar,and rubber pow der decreases the flexural strength,compressive strength and elastic modulus of CA mortar,and the higher the temperature,the smaller the compressive strength of modified CA mortar.The damping property of modified CA mortar was studied.The effects of the content of mica powder,hollow glass beads,rubber powder and temperature cycle on the damping properties of CA mortar were studied.The loss factor,storage modulus and dissipation modulus of CA mortar at different temperatures(20 ℃ ～50 ℃)and frequency(1 Hz～100 Hz)were measured by DMA(Dynamic Mechanical Analyzer).The results show that the loss factor of CA mortar mixed with 7.5% mica powder is the largest in the range of test frequency and temperature,which increases the ratio of 0.1% to 39.7%.The loss factor of CA mortar is slightly increased by adding hollow glass microspheres,and the storage modulus and dissipation modulus of CA mortar are greatly increased by adding rubber powder,and the loss factor of CA mortar is increased by addi ng rubber powder,and the storage modulus and dissipation modulus of CA mortar are decreased.The coupling model of vehicle-track system was established,and the influence of the stiffness and damping coefficient of CA mortar on the dynamic characteristics of vibration reduction of track structure was studied.The dynamic characteristics of track structure with different thickness and position of CA mortar are discussed,and the optimum track structure form was obtained.Then,the influence of stiffness and damping of CA mortar on its dynamic response and damping effect was discussed.The stiffness and damping coefficients of the optimal CA mortar were selected and compared with the control CA mortar.The results show that the slab track with 100 mm thick CA mortar layer between the concrete bearing layer and the roadbed has a certain damping effect,and the CA mortar with 7.5% hollow glass bead is compared with the control group.At the bottom of the CA mortar layer,the maximum acceleration level attenu ates 1.38%～9.48%. |
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