The Effect of Grain Size Distribution on Compression of Laterite Soil

Abstract

Laterite soil is often used as embankment soil in various civil constructions because this soil is widely available in South Kalimantan. However, it turns out that laterite soil is not suitable for use as embankment soil. This is because laterite soil has a fairly high plasticity index (PI) value, so improvement or stabilization efforts are needed to improve the soil quality.

In this research, a preliminary test was conducted to determine the physical and compression characteristics of the original laterite soil from Sungai Ulin, Landasan Ulin, and Mandiangin. After that, the main test was also carried out on laterite soil from the Sungai Ulin to determine the effect of the percentage of sands mixture in laterite soil on the consolidation parameters in the form of compression index (Cc), consolidation coefficient (Cv), swell index (Cs), coefficient of volume compressibility (mv), and permeability coefficient (k). The mixture of sand variation used in the test object is 0%, 7%, 14%, 21%, and 28%. Consolidated specimens were made with a density of 90% of the optimum moisture content.

The results of data analysis show that laterite soils from Sungai Ulin, Landasan Ulin, and Mandiangin are classified as Clay-High (CH) or high plasticity inorganic clays (fat clays). In addition, it is also known that laterite soil from Mandiangin has a higher compression index (Cc), swell index (Cs), and coefficient of volume compressibility (mv) than laterite soil from the Ulin River and Landasan Ulin. Meanwhile, laterite soil from the Sungai Ulin has a higher consolidation coefficient (Cv) and permeability coefficient (k) than laterite soil from the other two areas. Furthermore, data is obtained in the form of a graph showing the behavior of the mixture of sand fractions on the value of the compression index (Cc) and swell index (Cs) of laterite soils, when the percentage of the mixture of sand fraction increases, the values of the compression index (Cc) and swell index (Cs) decrease. The consolidation coefficient (Cv) also gets the effect by the percentage of the sand mixture. When the percentage of the mixture of the sand fraction increases, the value of the consolidation coefficient (Cv) also increases. The value of the coefficient of volume compressibility (mv) also decreases along with the increase in the percentage of the mixed sand fraction, the decreasing value is about 28.30%. In addition, the higher the percentage of mixed sand fraction in laterite soils, the value of the permeability coefficient (k) also increases, the increasing value is about 12.78%.

Keywords: laterite soil, compression of laterite soil, grain size distribution, sand fraction