Mineralogy, chemistry and the structure and microstructure of sediments

The geotechnical behaviour of sediments is influenced by mineralogy and various chemical factors. Interactions of mineralogy and water chemistry influence particle association and hence are determinants of the structure developed during sediment accumulation. Subsequent changes, during diagenesis and weathering, may change geotechnical behaviour. The argument that chemistry and mineralogy are critical aspects of sedimentary microstructure, because changes in them influence the geotechnical consequences of sediment disturbance, will be developed through discussion of: 1) essential requirements for high sensitivity and quick-clay behaviour in post-glacial marine sediments; 2) influence of oxidation/reduction processes on the behaviour of high-iron smectites, including implications for Ariake Bay, Japan, sediments; and 3) considerations in assessing the relative importance of carbonates, iron oxides and silica as cementing agents, especially when only minor amounts are present. These examples emphasize the geotechnical desirability of characterizing the mineralogy and in-situ chemistry land risk of their change), and the microstructure of geotechnically-problematic sediments.