Extended wet sieving method for determination of complete particle size distribution of general soils

The traditional standard wet sieving method uses steel sieves with aperture ≥0.063 mm and can only determine the particle size distribution (PSD) of gravel and sand in general soil. This paper extends the traditional method and presents an extended wet sieving method. The extended method uses both the steel sieves and the nylon filter cloth sieves. The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm, 0.038 mm, 0.014 mm, 0.012 mm, 0.0063 mm, 0.004 mm, 0.003 mm, 0.002 mm, and 0.001 mm, respectively. The extended method uses five steps to separate the general soil into many material sub-groups of gravel, sand, silt and clay with known particle size ranges. The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups. The extended method is demonstrated with a general soil of completely decomposed granite (CDG) in Hong Kong, China. The silt and clay materials with different particle size ranges are further examined, checked and verified using stereomicroscopic observation, physical and chemical property tests. The results further confirm the correctness of the extended wet sieving method.