Physio-mechanical evaluation of Nano-soil as an additive to the sand-bentonite mixture for Tabriz city landfill liner

The purpose of this paper is to introduce a suitable material for Tabriz city landfill liner by using local materials. For this reason, the soil was collected from the Tabriz landfill bottom, a new under-construction site (Iran). As an additive, the nano-soil was produced from landfill local soil using the pulverization of soil samples through a high-energy milling process. Chemical and physical tests including Atomic Force Microscopy (AFM) were conducted to determine the nano-soil features and topography. To obtain the minimum requirement for landfill liner soil application, 90% of Tabriz landfill soil was mixed with 10% of Bentonite. The resulting soil was identified as clayey sand with a plasticity index of 13%. Then, the effect of nano-soil on a sand-bentonite mixture as an economical and modern additive for Tabriz city landfill liner application was investigated. This investigation was based on laboratory experiments including compaction, direct shear, and hydraulic conductivity tests. The nano-soil was used as an additive in six different contents including 0.5, 1, 1.5, 2, 2.5, and 3% of soil dry weight. According to the results, with increasing nano-soil content, the maximum dry unit weight increased and the optimum moisture content of the mixture decreased. Moreover, by increasing nano-soil content by 2%, the shear strength and hydraulic conductivity experienced the desired positive effect for a landfill bottom liner, while the excess addition of nano-soil resulted in neglectable or even negative effects.