New washing and sieving method for separation and evaluation of soil particles to nano-size

Abstract

Soil particles comprise nano-sized clay particles, micro-sized silt particles, milli-sized sand particles, and centi-sized gravel particles. The proposed new washing and sieving method extends the existing standard wet sieving method and uses the nylon filter cloth to accurately separate the silt and clay mixture into different size groups of particles to nano-sizes. Through a large amount of particle images and experimental data, these separated particles from general soils can be an important source of new productive forces. The first part (Chapters 2 to 3) proposes a new washing and sieving method. This method extends the standard wet sieving method using steel sieves with aperture sizes ≥0.063 mm (or ≥0.075 mm) for gravel and sand particles separation and using nylon sieves with aperture sizes from 48 μm, 38 μm, 14 μm, 12 μm, 6.3 μm, 4 μm, 3 μm, 2 μm, 1 μm, 800 nm, 500 nm, 400 nm, 200 nm, to 100 nm, respectively, for silt and clay particles separation. The availability of nano-scale particles helps determine the cut-off size between clay mineral particles and silt particles, and study the properties of nano-clays in geotechnical applications. Both manual-based and machine-based methods are universal for particle separation with high accuracy. The stereomicroscopic and SEM images checking for individual particles verify the correctness of particle sizes. The proposed new washing and sieving method is conceptually straightforward, operationally simple, and material available. The second part (Chapters 4 to 7) establishes a refined approach to evaluate the geometrical, physical, chemical, and mineralogical properties of soil particles. Part I applies the proposed washing and sieving method to separate general soil into many sub-groups of particles with known size ranges. Part II uses standard laboratory test techniques to assess the properties of individual particles. These techniques include dynamic image analysis particle measurement, stereomicroscopy, scanning electron microscopy (SEM), Atterberg limits test, permeability test, energy-dispersive X-ray spectroscopy (EDS), X-ray fluorescence (XRF), and X-ray diffraction (XRD) tests. Based on the test results, the relationship between particle properties and particle size, as well as the relationship between the bulk behavior of soil and the properties of its constituent particles are accurately quantified. A specific type of soil such as completely decomposed granitic (CDG) or volcanic soil (CDV), marine deposits, and expansive soil can be quantitatively studied based on the properties of individual particles. The third part (Chapter 8) expands the proposed washing and sieving method for the basic soil classification of the other 45 types of soils from 37 sites throughout China. These soils are mainly collected from paddy lands, dry farmlands, forests, woods, natural hillside slopes, and public fill banks. Their particle size distributions, some physical properties, and refined soil names are briefly described in this part. The test results show that the new washing and sieving method is applicable to the separation and classification of many different types of soils from various sites, which helps establish the particle and mineral sequence map of soils on the ground and provides particle materials for further studies.