Strength and Permeability Characteristics of Fibre Reinforced Liner Material

Abstract

Sand-bentonite mixtures are widely used as liner material. After optimization, it is observed that sand-bentonite mixture with bentonite content 15% satisfies the criteria of compacted clay liner (CCL) material stipulated by United States Environment Protection Agency (USEPA). Bentonite is an expensive material. So, the focus of this study is to reduce the bentonite content with reinforcing the mix by random inclusion of poly-propylene fibres. In this study sand-bentonite mixture with 10%, 15% and 20% bentonite content are used and 0, 0.2, 0.5 and 1% polypropylene fibre by weight of the mixture is added. Unconfined compressive strength (UCS) test is done to observe the strength characteristics of the mixture. The UCS specimens are statically pressed to their respective maximum dry densities (MDD) at compaction water content equal to optimum moisture content (OMC). UCS values are determined at this molded water content as well as in fully saturated conditions. It is observed that the failure strength and ductility of a sample with a given bentonite content increases with increasing fibre content. It is also noticeable that normalized strain energy is increased and reduction of post peak strength is minimized with increasing fibre content. However, at particular fibre content, the strength initially increases up to 15% bentonite content and thereafter it reduces. This trend is observed for all the samples. The UCS value of sand-bentonite specimens, containing 15% bentonite and compacted at OMC with compactive effort of 595 kJ/m3, increases from 60.92 kPa to 483.46 kPa when the fibre content increases from zero to 1% i.e. which is 694 % increase of strength. Permeability test is done with distilled water under pressure head of 4 kg/cm2 to find out the effect of fibre content on hydraulic conductivity of the mixtures. It is noticed that inclusion of fibers reduces the hydraulic conductivity of the compacted sand-bentonite mixes. Scanning Electronic Microscopy (SEM) is performed to observe the distribution of fibres in the sand- bentonite mixture