Suitability of the Expansion Index for Paleogene Mudstone in Nanning Section of Guinan High-speed Railway

Paleogene mudstone in the Nanning section of the Guinan high-speed railway is a semi-formed mudstone deposited in lakes and marshes, which is easy to soften when it meets water or to disintegrate when it loses water and has certain swelling and shrinking properties. Based on the expansive test data of mudstone samples in the Nanning section of the Guinan high-speed railway and the actual phenomenon of herringbone skeleton cracking on cutting slope, the applicability of expansive discrimination indexes was studied by using analysis methods of correlation, linear regression, and matching degree. The results show that the grading results of single-index expansion potential by dry-saturated water absorption rate is close to the actual situation, and the grading results of single-index expansion potential of natural humidity samples by expansion force, cation exchange capacity, montmorillonite content or free expansion rate are easy to drop by 1-2 grades.