Deformation characteristics of unsaturated fine-grained moraine soil at high plateau airport with considering the moisture content and stress levels

This study examines unsaturated, fine-grained moraine soil from a high-plateau airport in the Tibetan region. Laboratory tests were conducted to determine key physical characteristics, including particle size distribution, optimal moisture content, maximum dry density, plasticity limits, and liquid limits. These tests provided baseline physical performance indicators for high plateau moraine soil. Considering the unsaturated environment in which this soil typically exists, the influence of matric suction on the vertical deformation was considered. Laboratory experiments were then designed with this stress factor in mind to explore how the soil’s vertical deformation responds to changes in stress under varying water levels. This study examined relationships between moisture content and three key indicators: compression index Cc compression coefficient av, and compression modulus Es. The results showed that, under the same stress, increased moisture content leads to greater vertical deformation in the soil. Similarly, at the same water level, higher stress produces greater compression. The compression index Cc is negatively correlated with moisture content, while the compression coefficient av shows a positive correlation and the compression modulus Es is negatively correlated. These findings provide valuable theoretical insights into the construction and maintenance of airport infrastructure in high plateau regions. At the same time, the matric suction, viewed as an internal resistance in fine-grained moraine soil, helps resist deformation under external stress, providing a hardening effect.