Determination of the design moisture content of road subgrade soils in arid regions of Kazakhstan

Abstract

The article considers the determination of the design moisture content of the subgrade working layer under arid climatic conditions in Kazakhstan. The study is based on field and laboratory investigations conducted on roads in the Zhambyl, South Kazakhstan and Kyzylorda regions. The design moisture content of light silty loam was evaluated for different moisture conditions of the subgrade working layer, both with and without freezing. Under non-freezing conditions, the calculated moisture content was 0.185 for the first moisture condition and 0.208 for the second and third moisture conditions. When the upper 0.20 m layer was frozen, the average calculated moisture content of the working layer increased to 0.192, 0.213 and 0.216 for the first, second and third moisture conditions, respectively. The required elevation of the pavement surface above groundwater and surface water levels was also assessed. It was established that prolonged surface water accumulation is the governing condition, requiring an embankment height of at least 0.95 m. The obtained results can be used in subgrade design and in selecting appropriate soil compaction technologies for arid and irrigated regions of Kazakhstan.