MODIFIED LOGNORMAL DISTRIBUTIO FUNCTION FOR MODELLING SOIL-FREEZING CHARACTERISTIC CURVE

Abstract

SWCC (Soil-water characteristic curve) and SFCC (Soil-freezing characteristic curve) are the main concepts describing the properties of unsaturated and frozen construction material, respectively. SWCC is the relationship between water content and matric suction of the soil and can be used for the understanding of unsaturated soil characteristics while SFCC demonstrates the relationship between the unfrozen moisture content of soil and sub-freezing temperature and can be used to predict the frozen soil behavior. The objective of this study is to develop new equation for modelling SFCC incorporating physical meaning of SWCC variables. SFCCs of natural soil from Turan Avenue near Nazarbayev University, Astana and engineered soil (sand-kaolin mixtures) are utilized to evaluate the proposed model. The laboratory experiments were conducted by measuring soil moisture and suction of the investigated soils under different temperatures. The determination of SFCC using the proposed model was compared with various mathematical equations. In addition, the effect of soil type was studied by utilizing mathematical SFCCs for a variety of soils, including Astana soil, sand-kaolin combinations, and SFCC envelopes based on the Unified Soil Classification System. Fine-grained soils exhibited a higher unfrozen water content, even at temperatures below -10 °C, due to their superior water absorption capabilities. The new SFCC model provided an important theoretical advancement by accurately describing SFCC fluctuations during freezing. Its examination utilizing experimental data from Astana soil revealed a better fit than the Fredlund & Xing (1994) SFCC model. A similar pattern was observed in the verification of sand-kaolin blends, with the slope of the SFCC graph rising as the amount of kaolin increased.