Characteristics and Mechanisms of Heave of High-Speed Railway Subgrade Containing Pyrite Filler

Pyrite oxidation expansion has significant engineering implications, easily inducing heave deformation in structures such as buildings, railways and highways. Through the field investigation, deformation monitoring and mineral composition analysis, this paper systematically analyzes characteristics of heave diseases in subgrade containing pyrite fillers, explores the correlation between heave deformation and the friction plate and end spine, as well as the height of subgrade filler, and analyzes the expansion reaction mechanism and characteristics of pyrite oxidation, so as to clarify the cause of subgrade heave. The results show that small amounts of pyrite and gypsum are detected in all subgrade fillers of the heave section. The heave deformation mainly occurs within the height range of subgrade, with a continuous heave rate of 0. 13 - 0. 46 mm · m-1 since the opening of the railway. The heave deformation of track structure in the half-filled and half-excavated section decreases along the transverse direction of subgrade with the decrease in the filler height. The vertical deformation characteristics of the track in the transition zone between the road and bridge are closely related to the structure of friction plate and end spine, which exhibit inhibitory effects on the subgrade heave deformation. Pyrite oxidation reaction is a long-term and continuous process, and the volume expansion accompanying the chemical reactions resulting from sulfate production is the main cause of subgrade heave deformation. To thoroughly eliminate this hazard, underground excavation and replacement measures should be taken for the filler-containing pyrite. © 2024 Chinese Academy of Railway Sciences. All rights reserved.