Refined evaluation approach for geometrical, physical and chemical properties of completely decomposed tuff soil particles

This paper presents a refined approach for evaluating the geometrical, physical, and chemical properties of weathered soil particles and illustrates it with a completely decomposed tuff (CDT) soil. This refined evaluation approach consists of two parts. Part I separates soil into 25 sub-groups of gravel, sand, silt, and clay particles from 14 mm to less than 0.0008 mm by washing and sieving. Part II applies laboratory tests to examine the refined geometrical, physical, and chemical properties of each sub-group of materials. These laboratory tests include the dynamic and static image analysis for particle shape evaluation, the Atterberg limits test for plasticity evaluation, the falling head permeability test for hydraulic conductivity evaluation, the energy dispersive X-ray spectrometer (EDS) test and X-ray fluorescence spectrometer (XRF) test for elemental composition evaluation, and the X-ray diffractometer (XRD) test for mineral composition evaluation. The quantitative results of these refined properties of the soil materials can be expressed as a function of the particle size. The characteristics of each sub-group of particles together determine the properties of the soil mixture. This refined evaluation approach provides a new insight for examining the properties of weathered soils and their weathering degrees.