Investigation on the sulfate attack-induced heave of a ballastless track railway subgrade

Continuous heave was observed in a High-Speed Railway subgrade section, which caused severe track irregularity and damage to the concrete structure. After exploring the current relevant research and the construction information of the heave section, this paper addresses the causes and characteristics of the deleterious heave. Displacement and temperature sensors were installed in field to investigate the heave and the ground temperature of different depths of the subgrade. Moreover, experiments were conducted to analyze the expansive potential, soluble salt content and mineral composition of the subgrade filling and ground soil using X-ray diffraction method. The results show that the sulfate attack-induced heave that usually occurs in cement stabilized fine aggregates can also occur in cement-treated graded macadam, and the heave can be attributed to the resultant ettringite and thaumasite. The sulfate attack-induced heave shows a high amount of relation to the ground temperature, and the reaction is more active when the ground temperature decreases from 15 degrees C to 5 degrees C. Furthermore, this paper intends to inspire more studies to propose efficient measures to mitigate and avoid the continuous heave.