Compatibility of Blended Lithomargic Clay as Landfill Liner Materials

Abstract

The present investigation is an experimental study on locally available lithomargic clay (shedi soil) and blended lithomargic clay as a suitable soil liner material for the effective containment of leachate in landfills. The objectives of the research work were accomplished in three phases. First phase of work deals with geotechnical characterization of test soils. Hydraulic conductivity is considered as most significant factor for performance of a clay liner. Results obtained show that the hydraulic conductivity of lithomargic clay is greater than the suggested limit of k<10-7cm/s by various waste regulatory agencies. To reduce hydraulic conductivity of lithomargic clay, it is blended with black cotton (BC) soil and bentonite at different proportion till the required hydraulic conductivity (k <10-7cm/s) was achieved. Lithomargic clay blended with 5% and 10% of a black cotton soil and, lithomargic clay blended with 5% and 7.5% of a bentonite satisfied the hydraulic conductivity requirement of liner material. Hence blend proportions were considered for further investigation. The compatibility of a clay liner on interaction with contaminant depends on its capacity to retard the migration of contaminants through sorption. In the second phase studies related to adsorption characteristics of soil samples through batch tests have been carried out. The experimental results of batch adsorption tests have been analysed using three adsorption isotherms. Adsorption coefficient of study soils shows that, adsorption of potassium, lead and nickel are more on BC soil and bentonite while lithomargic clay adsorbs more chloride and chromium. As a result blending of lithomargic clay with BC soil and bentonite, the adsorption of contaminants is found to be more in the blended soils compare to parent soil. In the third phase of the research work, the effect of interaction of leachate on behaviour of lithomargic clay and blended lithomargic clay has been studied. The hydraulic conductivity has been found to decrease in both, the natural and the blended lithomargic clay due to the leachate interaction. Blended lithomargic clays has been found to be beneficial in terms of achieving lower hydraulic conductivity, adequate strength, minimal potential to shrinkage. All these properties make blended lithomargic clay as a potential soil liner material for various geoenvironmental applications.