Index Property to Characterize the Proportion of Primary Minerals Transforming to Clay Residues During Expansive Soil Formation

Rao, SM (2022) Index Property to Characterize the Proportion of Primary Minerals Transforming to Clay Residues During Expansive Soil Formation. In: Geotechnical and Geological Engineering .

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Abstract

Abstract Disintegration and decomposition of sedimentary materials and igneous/metamorphic rocks in arid and semi-arid plateaus form expansive soils. The parent materials of expansive soils are 5.3 million years (basic igneous rocks) to > 570 million years (basement complex rocks) old. Developing an index property to estimate the fraction of primary minerals that decompose to clay is important as expansive clays drive their moisture-related volume changes. Data of 119 expansive soils from Nigeria, Tanzania, Ethiopia, Sudan, India, Australia, Oman, Chad Basin, Morocco, Kenya, and Zambia are analyzed to develop an index property termed decomposition ratio (Dr) to quantify the fraction of primary minerals that decompose into expansive clay. The sand+silt fractions represent the undecomposed primary mineral content, while the clay fraction represents the fraction of primary minerals that decomposed completely. Expansive soils from India, Sudan and Tanzania are characterized by median Dr values of 0.52–0.74; expansive soils from Ethiopia, Nigeria, Australia, Ghana, Chad Basin, Morocco, Zambia, and Kenya are characterized by median Dr values of 1.02–1.43. Dr values < unity imply that < 50% of primary minerals have decomposed into clay. Analysis of Dr data indicated that clay formation tends towards equilibrium when weathering of parent material depletes their primary mineral contents to 35%. Normalizing liquid limit with Dr regulates variations in liquid limit of expansive soils with similar clay content but formed under different conditions.

Item Type:	Journal Article
Publication:	Geotechnical and Geological Engineering
Publisher:	Springer Science and Business Media Deutschland GmbH
Additional Information:	The copyright for this article belongs to the Springer Science and Business Media Deutschland GmbH.
Keywords:	Clay minerals; Digital storage; Disintegration; Igneous rocks; Lithology; Sedimentary rocks; Soils, Australia; Decomposition ratios; Environment; Ethiopia; Expansive clays; Expansive soils; Index properties; Nigeria; Parent materials; Tanzania, Weathering
Department/Centre:	Division of Mechanical Sciences > Civil Engineering
Date Deposited:	03 Sep 2022 05:35
Last Modified:	03 Sep 2022 05:35
URI:	https://eprints.iisc.ac.in/id/eprint/76407

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