The shear strength alteration on clay soil considering the plasticity index and the percentage of fine aggregates in tropical climate regions

Seasonal changes in tropical regions could cause variations of soil water content, especially in clay soil. Furthermore, there is a significance difference in shear strength between wet and dry clay soil which depends on the plasticity index and the percentage of fine aggregates. Laboratory experiments were conducted to investigate the effect of the plasticity index and the percentage of fine aggregates in clay soil on soil shear strength changes due to water content variation. Soil samples were obtained from five locations in Surabaya City, Indonesia. The soil characteristics were tested in a laboratory to obtain the initial water content, Atterberg limits, specific gravity, and soil size distribution. The next stage was drying the soil samples. Each one was stored at room temperature to reach the determined soil weight. The shear strength of the soil in initial and drying conditions was determined by an unconfined compression test. The results indicated that the lower the moisture contents of soil, the greater the shear strength of soil, and vice versa. Soil shear strength changes up to 52 times within the range of 36% to 72% of moisture content The results also show that the value of shear strength variation depends on the plasticity index and the percentage of fine aggregate