Water-induced disintegration behaviour of Malan loess

The Malan loess is a greyish yellow unstratified sediment with uniform lithology, large pores and loose texture. The Malan loess is sensitive to water due to its porous and metastable structure. Water-induced disintegration is the main cause of soil loss in the Loess Plateau of China and the primary evolutionary driving force of the loess landform. A series of laboratory tests is conducted on undisturbed cylindrical Malan loess samples to understand their disintegration behaviour further and examine potential influencing factors. Results show that the Malan loess experiences primary and secondary disintegration stages. The primary disintegration occurs very fast and terminates in an average of 40 s. Approximately 78% of the soil disintegrates in this stage. The disintegration velocity (V) and percentage (D-f) in the primary stage demonstrate high correlation with the dry density, clay mineral content and CaCO3 content. Specifically, D-f increases while V decreases with the increase of dry density or clay content. D-f decreases while V increases with the increase of CaCO3. The concentration of ions, including Cl-, SO42-, CO32-, HCO3-, Ca2+, K+, Na+ and Mg2+, and the organic matter content do not exhibit a clear relationship with D-f and V. In addition, the pore structure influences the Malan loess disintegration. The soil with evenly distributed small pores is subjected to gradual disintegration from outside to inside without abrupt failure, while that with large pipes disintegrates abruptly in large pieces.

Automated summary

The Malan loess is a greyish yellow unstratified sediment that is sensitive to water due to its porous and metastable structure. Results from laboratory tests show that the Malan loess experiences primary and secondary disintegration stages, with the primary stage showing high correlation with dry density, clay mineral content, and CaCO3 content. Additionally, the pore structure of the soil influences the disintegration behavior, with evenly distributed small pores leading to gradual disintegration and large pipes leading to abrupt failure.