Computer microscopic test study on the suitability of modified polyimide grease used to improve collapsible loess railway subgrade

The stability and permeability of the collapsible loess are poor, and the infiltrated water in the loess is difficult to drain out. Due to the dynamic loads induced by trains, the collapsible loess railway subgrade is prone to instability and liquefaction. In this paper, an organic polymer material, Modified Polyimide Grease (MPG) produced was proposed to treat the collapsible loess railway subgrade. The scanning electron microscope, FTIR, and X-ray diffraction methods were used on the study of the mechanism of MPG. The results indicated that an optimum MPG content of 2.5%, approximately 3 day, could achieve the highest strength and result in the best softening coefficient. After being treated by MPG, the permeability of the loess samples was slightly decreased compared to that of untreated samples, which indicated MPG could improve the strength of the loess without significantly reducing its permeability. This property was suitable for the subject MPG treated loess subgrade to achieve a reasonable drainage. Besides, it is observed that some portions of pores in loess samples were filled by MPG and the strength between the particles was increased. The research results indicated that MPG is a suitable material to improve collapsible loess railway subgrade in the subject area.