Soil Classification System

Lab Report #4:

Soil Classification using USCS and AASHTO System

Soil classification is basically the identity of a soil based on its characteristics and properties. Soils may be classified into groups and sub-groups. Two classification systems utilized in this activity were Unified Soil Classification System (USCS) and American Association of State Highway and Transportation Officials (AASHTO) classification system. Two previous experiments, namely, Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis; and Liquid Limit, Plastic Limit, and Plasticity Index of Soils, provided the data used in the activity. These inputs were simple index properties such as particle-size distribution and plasticity. The results were group SW,

These inaccuracies stem from the previous two experiments, namely, Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis; and Liquid Limit, Plastic Limit, and Plasticity Index of Soils. Some worth noting are the following. The sieve used had weaving defects, creases, wrinkles, and foreign matter. The balance could not measure the mass precisely and sometimes shows negative value when it is supposed to be zeroed. The sample was not really pure and contaminated for there are roots of plant matter included and small glass shards. Following the instruction of covering the moist specimen to retain moisture was not sometimes implemented due to shortage of covers. If only these were avoided, i.e. new sieves and soil without extraneous matter, the error would be much more

The activity incorporated results from previous two experiments, namely, Particle-Size Distribution (Gradation) of Soils Using Sieve Analysis; and Liquid Limit, Plastic Limit, and Plasticity Index of Soils. The first one provided the sieve number, mass retained (g), Cumulative Mass Retained (g), Percent Retained, Cumulative Percent Retained, Sieve Size (mm), and Percent Passing, PPN. These were used to get effective size (D10 or 10% finer); 30% and 60% finer; uniformity coefficient (Cu); coefficient of gradation (CC); sorting coefficient (S0); gravel, sand, silt and clay size particles; and percentage distribution. Plasticity Index (PI) and Liquid Limit (LL) were derived from the second one. For the AASHTO classification system, the percentage passing of sieves Nos. 10, 40, and 200; plasticity index (PI); and liquid limit (LL) were employed to the Classification of Highway Subgrade Materials table and group index was also computed, thus, resulting to group A-2-7(0), silty or clayey gravel and sand. Percentage passing No. 200 sieve, fine and coarse fractions, uniformity coefficient, and coefficient of gradation were put into use to get group SW, well graded sands, gravelly sands for the USCS. The comparison table between the two systems showed that the results were possible but improbable.