Compressibility and the Effects of Structure of Tropical Clay in Incremental Loading Oedometer Tests
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ORIGINAL PAPER
Compressibility and the Effects of Structure of Tropical Clay in Incremental Loading Oedometer Tests Ismail Adeniyi Okewale
Received: 26 September 2019 / Accepted: 16 May 2020 Ó Springer Nature Switzerland AG 2020
Abstract Several problems in geotechnical and geological engineering have been analysed based on the properties of soil obtained from compression tests and the behaviour in compression is a fundamental aspect of deformation in geomaterials. A detailed analysis has been made into the mechanics of compression of Nigeria tropical clay in incremental loading oedometer for the soils in the reconstituted and natural states, allowing for the effects of geological structure. In addition to classification and index tests, microstructure and geochemistry were studied using SEM equipped with EDS and mineralogical indices were investigated using XRD for the soils retrieved from different depths and two locations. The soils are heterogeneous and the spatial variability is low. The soils have low plasticity and clay minerals are dominated by kaolinites. The soils converged to unique intrinsic normal compression lines showing no transitional mode of behaviour. The intrinsic behaviour of the soils was consistent with fines content, plasticity and clay minerals. The finer and better-graded soil with higher fines content, plasticity and clay minerals content have higher compressibility. The effects of structure, which is the degree of enhanced resistance of the natural sample in compression, were positive and small to medium.
I. A. Okewale (&) Department of Mining Engineering, Federal University of Technology Akure, P.M.B. 704, Akure, Ondo State, Nigeria e-mail: [email protected]
Keywords Tropical clay Microstructure Mineralogy Compressibility Geological structure Geotechnical properties List of Symbols Cc Compressibility index CF Clay fraction Cu Coefficient of uniformity D50 Mean particle size e Void ratio eo In-situ void ratio e*100 Void ratio at 100 kPa e*1000 Void ratio at 1000 kPa fc Fines content LL Liquid limit mv Intrinsic coefficient of compressibility NCL One-dimensional normal compression line No Intercept of NCL at 1 kPa PL Plastic limit PI Plasticity index v Specific volume w Initial/natural water content ev Vertical strain rv’ Vertical effective stress ry’ Yield stress De Change in void ratio k Slope of NCL
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Geotech Geol Eng
1 Introduction A comprehensive understanding of compression behaviour of geomaterials is essential particularly in deformation calculations and numerical modelling. Investigation into mechanical behaviour of clays is very important due to challenges they pose for safe and economical design of engineering structures in them. Some studies have been carried out on clays (e.g., Burland 1990; Cotecchia and Chandler 2000; Gasparre and Coop 2008; Horpibulsuk et al. 2011; Mataic et al. 2015) but similar investigation is very scarce for Nigeria tropical clays and this is necessary due to variable nature of cla
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