Influences of train speed on permanent deformation of saturated soft soil under partial drainage conditions

摘要

To better understand the cumulative settlement of railway ground under the repeated train loads, the effects of cyclic stress (sigma(d)), initial static shear stress (sigma(s)), and effective mean principal stress (p(0)') on the permanent deformation of saturated silty clay are examined and evaluated through a series of cyclic load triaxial tests under the partial drainage conditions. As the results, the permanent strain of soil under different test conditions increases exponentially with the increase of Cyclic Stress Ratio (CSR = sigma(d)/2p(0)'), which can be predicted by an empirical prediction formula, irrespective of the cyclic stress (sigma(d)) and the effective mean principal stress (p'(0)). Besides, the influence of different embankment stiffness and train speed on the distribution of cyclic stress (sigma(d)) railway ground is analyzed by a three-dimensional (3D) numerical simulation. For ballastless track structures, reducing stiffness of embankment slightly affect cyclic stress (sigma(d)) on the railway ground, whereas increasing train speed significantly increases cyclic stress (sigma(d)) on the railway ground. Furthermore, the cumulative settlement of soft soil ground calculated by the Chinese code method (CM) and the dynamic method (DM) considering the train speed is compared, which indicates that CM may underestimate the settlement value of railway ground when the train speed increases (i.e., v = 112 m/s).