Engineering geological properties of weathered swelling mudstones and their effects on the landslides occurrence in the Yanji section of the Jilin-Hunchun high-speed railway

To identify the mechanisms that caused landslides during the construction of the Jilin-Hunchun high-speed railway line in Yanji, China, the engineering properties of weathered swelling mudstones extracted from a representative landslide site were investigated. The experimental results indicate that both yellow-brown and magenta mudstones exhibit significant swelling and shrinkage behaviour due to significant amounts of swelling clay minerals. The yellow-brown mudstone has an obvious schistose structure with stacked flaky plates interconnected with a face-to-face pattern, while the magenta mudstone has an aggregated structure cemented by iron oxides. Both mudstones are prone to disintegration when soaked in water. The shear strengths of swollen samples decrease dramatically compared with those of unsaturated samples, and the lower the initial water content is, the smaller the shear strength of a sample after swelling. By repeatedly increasing the repeated drying-wetting-freezing-thawing cycles, the shear strength decreases. According to the experimental findings, the effects of the engineering properties of mudstones on the landslides occurrence in the Yanji section are discussed. Heavy rainfall and the weathering of mudstones induced by fluctuating climatic conditions are regarded as the principal factors that triggered the landslides. Given the high landslide incidence on south-facing slopes, the influence of slope orientation on the stability of mudstone slopes is studied and discussed.