Influence of Coarse Fraction on Swelling Characteristics


K. Mallikarjuna Rao

Associate Professor, Dept of Civil Engineering, Sri Venkateswara University, Tirupati

G. Giri Babu

Post Graduate student, Dept of Civil Engineering, Sri Venkateswara University, Tirupati

Ch. Sudha Rani

Research Scholar, Dept of Civil Engineering, Sri Venkateswara University, Tirupati


Expansive soils are known to cause severe damage to structures resting on it. Safe and economic designs of foundations on these soils require the knowledge of swelling characteristics viz., swelling pressure, swell potential, and swelling index. The direct determinations of swelling characteristics require considerable time and money involving the services of trained technicians and expert geotechnical engineers. Ever since the expansive soils are identified, the geotechnical engineering community is engaged in developing empirical regression models for estimation of swelling characteristics from easily determined Atterberg’s limits and placement conditions. This investigation aims at studying the influence of fraction coarser than 425µ on swelling characteristics which received little attention but plays vital role as Atterberg’s limits are determined on fraction passing 425µ sieve. The study reveals that the coarse fraction does influence all the swelling characteristics viz., swell potential, swell pressure and swelling index.  Empirical regression models have been established to estimate the modified swelling characteristics having known the fraction coarser than 425µ.

Keywords: Expansive soils, regression, empirical correlation, coarse fraction

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