CA Mortar Fatigue Damage And Its Effect On Vibration Response Of Track Structure

As the elastic cushion in the ballastless track of the high-speed railway, the CA mortar layer must bear kind of property deterioration under the coupling load with high frequency vibration. In this paper, effect of vibration frequency on the fatigue of the CA mortar was studied by using a service environment simulated experimental setup. An equivalent uniaxial damage constitutive model was selected to describe the constitutive relations between stress and strain of the CA mortar under different vibration frequencies. Furthermore, the effect of the property deterioration of the CA mortar on the vertical dynamic response of slab track structure was investigated by using Abaqus finite element method. According to the testing results and the theoretical analysis, it is concluded that:1) Under the same mixture ratio, high and low temperature, vibration stress and the time of fatigue, variations of the compressive strength and elastic modulus of the CA mortar after fatigue service with the increase of vibration frequency were piecewise linear approximation relationship, its value with the increase of vibration frequency first increased then decreased; the deformation ability of the CA mortar after fatigue service was poor, presenting the typical characteristics of brittle material, material ductility and toughness; Mixing polymer emulsion can significantly improve the anti-fatigue performance of CA mortar, and prevent the premature loss of elasticity for adjustment.2) By using "Nanshui" nonlinear model, the quasi uniaxial compressive stress and strain state of the CA mortar under the standard curing can be well fit.Through introducing damage variable in the selected model, an equivalent uniaxial damage constitutive model was developed to describe the constitutive relations between stress and strain of the CA mortar after fatigue service; the model parameters and vibration frequencies(equivalent to fatigue loading times) had certain change rule, at the same time with strong physical meaning.3) The effect of the property deterioration of the CA mortar on the vertical dynamic response of slab track structure was investigated by using Abaqus finite element method. Results showed that with the increase of elastic modulus of CA mortar, the most unfavorable stress increased gradually in the CA mortar layer, and maximum vertical displacement of rail and track plate all showed a trend of decrease at the same time; the maximum vertical acceleration of rail and rail board, however, had a trend of decrease in the former and increase in the latter, it was not conducive to the safety of the track structure. With the increase of CA mortar elastic modulus, natural vibration frequencies of track structure in order and high order existed increasing areas; the structure will increase the likelihood of resonance between track structure and car body when the frequencies increased too much.