Physio-mechanical properties of loess-paleosol sequences over the past 400 ka and their paleoclimate controlling factors on the central Loess Plateau

Abstract

Exploring the relationship between the physio-mechanical properties of the loess-paleosol sequences and the paleoclimate can help provide essential references for engineering construction in the Chinese Loess Plateau, revealing the vital application value of Quaternary climate research. Continuous loess-paleosol sequence in the central Loess Plateau was selected to determine its physio-mechanical and chemical characteristics. The main results show: (1) During the interglacial period, the East Asian summer monsoon intensified, and the cementation of clay minerals made the soil structure dense under more precipitation, increasing soil cohesion. During the glacial period, the East Asian winter monsoon was stronger, and the loess's unstable microstructure was formed under the weak pedogenesis, increasing the compressibility and collapsibility. (2) The alternation of cold-dry/warm-humid climate in the Quaternary is the fundamental reason for the differences in physio-mechanical properties and structural strength between loess and paleosol; pedogenesis plays a direct decisive role. The impact of compaction after burial on the physio-mechanical properties of loess-paleosol sequences is less than that of pedogenesis. (3) Precipitation plays a dominant role in the shear strength and compressibility of loess-paleosol sequences, while precipitation and temperature jointly affect the collapsibility. A quantitative relationship between paleoclimate and physio-mechanical properties was established.