What analysis is used to determine the particle size distribution of fine-grained soils?

• A. Hydrometer analysis
• B. Mechanical sieve analysis
• C. Triaxial test
• D. Atterberg limits analysis

Answer: (A)

The analysis used to determine the particle size distribution of fine-grained soils is hydrometer analysis. This technique is particularly effective for fine particles, such as silts and clays, which are too small to be accurately measured using mechanical sieve analysis.

In hydrometer analysis, a sample of soil is dispersed in water, and the specific gravity of the suspended particles is measured using a hydrometer over time. The sedimentation of particles is governed by Stokes' law, which allows for calculation of the particle size distribution based on their settling velocities. This method is valuable in geotechnical engineering as it provides insights into the soil's texture, compaction characteristics, and potential behavior under load.

Other methods mentioned, like mechanical sieve analysis, are better suited for coarser materials such as sands and gravels. The triaxial test is used to assess the shear strength of soils, and Atterberg limits analysis determines the plasticity characteristics of fine-grained soils but does not provide information about particle size distribution. Thus, hydrometer analysis is the appropriate choice for assessing the particle size distribution of fine-grained soils.