Study of critical dynamic stress and deformation law of graded gravel under different moisture content

To evaluate the effect of changes in moisture content on the dynamic performance of graded gravel in the surface of ballastless track subgrade bed of high-speed railway, large scale indoor dynamic triaxial experiments were carried out on the dynamic performance of graded gravel under the two conditions of optimum moisture content and moisture saturation, to study the critical dynamic stress and the cumulative deformation characteristics of graded gravel. The research results indicated that the cumulative deformation was closely related to the number of load cycles and the moisture content. The influence of moisture content on the cumulative deformation gradually emerged when the load cycle number exceeded 10000. The cumulative deformation under the condition of saturated water content increased by 70% relative to that under the state of optimum moisture content, when the load cycle number exceeded 20000. The cumulative deformation curve of graded gravel with different moisture content under the attenuation state and the breakdown state can be simulated by Stewart model and Monismith model respectively. The critical dynamic stress of graded gravel decreased with the increase of moisture content while increased with the increase of confining pressure. The critical dynamic stress at the state of saturated water content was reduced on average by 13% compared with that at the state of optimum moisture content. © 2016, Editorial Office of Journal of the China Railway Society. All right reserved.