Expansibility classification of mudstone for high-speed railway ballastless track foundation

Red mudstone is a typical Jurassic sedimentary rock. It contains trace clay minerals, which is easy to soften in water, disintegrate when dehydrated, and has a certain swelling property. Red mudstone is an important factor that causes the continuous uplift of the subgrade for the Lan-Xin high-speed railway. Therefore, it is of great significance to redefine the expansibility of this kind of soil for the design and construction of ballastless track of high-speed railway. For this reason, the equivalent smectite content, cation exchange capacity, free expansion rate and liquid limit are selected as the indicators of mudstone expansion. The classification criteria for the expansion potential of the mudstone in the foundation are determined through a large number of field testing data. The weight of classification index combination is determined by using improved analytic hierarchy process (AHP), Gini coefficient method and intuitionistic fuzzy theory. The intuitionistic fuzzy comprehensive evaluation model of foundation mudstone swelling property is established based on the technique for order preference by similarity to ideal solution (TOPSIS method). The intuitionistic fuzzy comprehensive evaluation model quantifies mudstone swelling, and overcomes the shortcomings of different indicators of the same sample belonging to different levels. The applicability and accuracy of mudstone classification standard and intuitionistic fuzzy theory evaluation method to Lan-Xin high-speed railway are verified by laboratory expansion tests. The research results provide technical support for the risk assessment and control of long-term continuous uplift of red mudstone foundation for high-speed railway subgrade.