“Microstructure” method for engineering-geological evaluation of clay and loess soils (the right-bank adjunction zone of Academic Bridge / Academichesky most, Irkutsk)

The aim of the work has been to introduce a new method in the soil microstructure study for the clay and loess soils uncovered by well-drilling in the right-bank junction zone of Academic Bridge / Academichesky most, Irkutsk. The microstructure information block is usually unavailable in engineering-geological survey, though it is often one of the leading factors in evaluating the soil properties. Along with the study of the soil microstructure, the data on the soil plasticity has been used in the predictive calculations of the plasticity number at the yield point, in order to further substantiate the proposed method. Using the "Microstructure" method, the total aggregate content has been defined, including the prevailing fine fine-sandy, primary (unbound) fine-sandy, primary coarse-dust, and fine-dust particles; real clay content (clay fraction content in a free and aggregate state) has also been defined. In the course of the statistical data processing, the average values of the above parameters contents have been calculated, and their variability in the studied object group has been estimated using the variation coefficient. The soil skeleton-aggregated microstructure type defined by the total aggregate content shows a high real content of the clay fraction. Based on the average values of the selected parameters content, a special graph has been plotted, that reflects the parameters ratio for the studied objects. The comparison between the plasticity number values calculated by the predictive formulas and the experimental data shows a high matching degree in relation to the soil designation by the standard classification.

“Microstructure” method, clay soils, loess soils, plasticity number, cluster analysis

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