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The potential fields of application of fly ash in large volumes are mainly construction of roads, embankments, and filling of low lands. Shear strength of fly ash is one of the important parameters required for the design of such projects. To study the variation of shear strength parameters of fly ash with varying composition, unconsolidated undrained triaxial tests have been conducted on nine fly ash samples collected from different thermal power plants of the Eastern part of India. This paper presents shear strength parameters of all the nine fly ash samples, compacted at  optimum moisture content and maximum dry density obtained from standard Proctor (AASHO) compaction tests. All the fly ash specimens were tested under three different confining pressures of 100, 200 and 300 kPa. Effects of confining pressure, MDD and OMC on shear strength parameters of fly ash samples are discussed herein. The values of the shear strength parameters i.e., angle of internal friction, fuu and apparent cohesion, cuu of all the fly ash samples vary within the range of 29.91°–36.93° and 14.31–59.59 kPa respectively. As confining pressure (s 3) increases the shear strength (S) of fly ash increases, irrespective of type of fly ash. Effect of confining pressure (s 3) on deviator stress at failure (q¦) is more prominent for the fly ash samples of low strength than for fly ash samples of high strength. The angle of internal friction of the strength of fly ash samples is more significant than apparent cohesion, irrespective of type of fly ash. The friction angle fuu of the fly ash was found to be a function of the type of fly ash. The postpeak behaviour of all the fly ashes indicated brittle rupture in which axial strain values of almost all the fly ash samples are less than 15%.

IGC 2009, Guntur, INDIA
National Institute of Technology
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