Abstract
To investigate the evolving characteristics of plastic deformation for the angular gravels that are used to construct subgrade bed, a laboratory model test is performed with cyclic load applying. Vertical deformation is measured in real time by displacement transducers and further modified to analyze the plastic behavior of model fillings. It can be found that vertical plastic deformation shows quite different developing patterns under the effect of different cyclic amplitudes for a given model. A power function is adopted to describe the relationship between deformation rate and loading times. By analyzing the value of the power exponent and the corresponding developing features of plastic deformation rate, model filling status can be classified into four different zones, i.e., rapid stabilization, tardy stabilization, tardy failure, and rapid failure. Such a classification reveals different developing patterns of plastic deformation and satisfies the design of subgrade bed for ballasted and unballasted railway.
Highlights
Due to rapid operating trains, high-speed railway raises more rigorous requirements for smoothness and stability of rail track
In China, well graded angular gravel is recommended to fill surface layer, while round gravel, pebble, gravelly sand, and soil should be adopted to build the bottom layer of subgrade bed
Modification for Plastic Deformation Curve. It is described in Boltzmann superposition principle (BSP) that the effects of external loads applied at different moments are linear when they are continued till some later moment [22]
Summary
Due to rapid operating trains, high-speed railway raises more rigorous requirements for smoothness and stability of rail track. The first is to develop numerical analysis model to predict the development law of cumulative deformation with increasing loading times [7,8,9,10,11,12,13] This method aims at evaluating the final definite value of the plastic deformation. It is obvious that both stabilization and collapse can be differentiated into the rapid one and tardy one This grouping conception is of great significance for the design of subgrade bed in terms of cumulative deformation. Despite the difference of limiting value of cumulative deformation between ballasted and unballasted track in high-speed railway, both types of rail tracks should tend to stabilization under billions of cyclic loading times. A power function model has been established to describe the evolvement characteristics of plastic strain rate against cyclic loading times. The conclusions will provide guidance for the design of subgrade bed for both ballasted and unballasted track
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