EFFECT OF FLY ASH ON GEOTECHNICAL PROPERTIES OF LOCAL SOIL-FLY ASH MIXED SAMPLES

Tanaya Deb, Sujit Kumar Pal

Abstract: The primary fuel of thermal power plants i.e. coal generates significantly huge quantities of solid byproduct as fly ash, bottom ash and pond ash (called fly ash in this study). Fly ash have been collected from Kolaghat Thermal Power Plant, Kolaghat, West Bengal, India. Concerning the major challenges regarding the safe reuse, management and disposal of these wastes an attempt has been made to mix fly ash at 10, 15, 20, 25, and 30% on the basis of dry weight with local silty-clay soil (Sand= 10.65%, Silt= 52.35% and Clay = 37.00%). The local silty-clay soil collected from river bank near to NIT, Agartala, Tripura, India. The study is carried out through large scale tests to simulate field conditions as closely as possible and found to be a very effective means to control the specific gravity (G), liquid limit (LL) and plastic limit (PL), linear shrinkage (L-S), initial void ratio (ei), initial degree of saturation (Si), maximum dry density (MDD) and optimum moisture content (OMC) at standard Proctor compaction energy, hydraulic conductivity (k), unconfined compressive strength (UCS), free swelling index (FSI), and swelling potential (SP) characteristics. With increase of fly ash contents in the soil-fly ash mixed samples specific gravity, linear shrinkage, plasticity, MDD, Si , UCS, FSI, and SP have been decreased and OMC, ei increased. Depending on above percentages of fly ash in mixed samples hydraulic conductivity values achieved for soil, soil mixed with 10% of fly ash (Kolaghat fly ash), and soil mixed with 30% of fly ash (Kolaghat bottom ash) are 8.60 10-9 cm/s, 3.50 10-8 cm/s, and 1.53 10-7 cm/s respectively. Up to 30% of fly ash contents in soil-fly ash mixed sample, this material can be used as liner. 30% of fly ash contents or above in soil-fly ash mixed sample, this material may be used as land filling and embankments in the field of geotechnical engineering construction.

Keywords: fly ash, silty-clay soil, specific gravity, liquid limit and plastic limit, linear shrinkage, maximum dry density, optimum moisture content, initial void ratio, initial degree of saturation, hydraulic conductivity, unconfined compressive strength, free swelling index, swelling potential.

DOI: https://doi.org/10.15623/ijret.2014.0305094