Desiccation cracking is a common, undesirable phenomenon in many geotechnical engineering applications, particularly in compacted clay liners as it causes significant changes to the hydraulic and mechanical properties of soils. This is one of the major concerns in design and construction of landfill clay liners in arid regions. This paper reports the findings of laboratory tests conducted to investigate the effects of adding nylon fibre, guar gum and organic enzyme to the soil to control desiccation cracks. Merri-Creek clay, a highly expansive soil from Victoria, Australia, was used in the tests. The additives were mixed with soil in different combinations and in varying proportions. Desiccation tests were conducted in thin, long moulds as in the free shrinkage tests. It was observed that very small quantities of these additives were sufficient to alter the properties of overall mixture. The results indicated that fibre – enzyme is the most effective combination to reduce desiccation cracks. This additive combination contained 0.3% percent of fibres by dry weight of soil and 0.35 g of enzyme per kg of dry soil. There was a modest improvement in dry density in the fibre -enzyme mixture compared to pure Merri-Creek clay. Fibre-enzyme combination also showed the ability to reduce the hydraulic conductivity. It was discovered that guar gum is not desirable to mix with clays in terms of reducing desiccation cracking or decreasing hydraulic conductivity.
Shrinkage of clay soils during drying can impose significant unfavourable effects on engineering applications. Researchers have attempted to amend drying shrinkage by mixing soil with various additives such as nanomaterials, fibre, geo-polymer etc. This paper discusses the shrinkage characteristics of an expansive clay mixed with nylon fibre and an organic enzyme. As clay is mostly used in compacted form in civil engineering applications, the study was focused on the shrinkage behaviour of compacted clay. Different percentages of nylon fibre, ranging from 0 to 1.2 percent by weight, were mixed with soil. The amount of enzyme added to each mixture was kept fixed at 0.35 g of enzyme per kg of dry soil. Compacted soil blocks were made using standard compaction procedures and cut in to rectangular specimens of size 80 x 60 x 40 mm.Compaction test results indicated that addition of fibre and enzyme can slightly improve the dry density of soil. Rectangular block specimens were allowed to dry without restraints under room temperature. Change in moisture content, linear and volumetric shrinkage and change in void ratio were investigated. Image analysis techniques were used to measure the changes in dimensions.