Effect of Salt Solution on Plasticity and Permeability of Vietnam’s Soil Liners

In Vietnam, there are a lot of landfills to block pollutants and one of materials used for impermeable liners is soil liners (soil – bentonite mixture). In order to use as impermeable liners, the properties of soil liners such as plasticity and permeability were affected by many salt solutions which are leaching from decomposition of waste materials in the landfills. Those salt solutions can reduce the stable of impermeable liners. So, this paper presents a series of experimental studies in the laboratory to investigate the effect of some salt solutions on the properties of compaction, consolidation and plasticity of soil liners. The experimental results indicated that the salt concentration effected complex on the Atterberg limits and the vertical coefficient of permeability. It also found that increase in the salt concentration from 0N to 0.05N cause increase in plasticity index, liquid limit and decrease in the vertical coefficient of permeability. After that, the increasing of the salt concentration up to 1N resulted in decrease in the liquid limit and plasticity index and increase in the vertical coefficient of permeability increases.

Computer Modeling Approach of Leachate Flow in Compacted Laterite Soil Liner

The use of hydraulic barriers in sanitary landfills has become an impeccable means of protecting the groundwater system from leachate. A question to be asked is, can these barriers continue to impede the migration of leachate over a long period? This paper investigates the phenomenon of leachate migration in compacted laterite soil used as liner in sanitary landfills. An experiment was carried out using laterite soil compacted at optimum moisture content using Standard Proctor energy. Leachate was poured on the compacted soil in an acrylic column and its migration was monitored using Digital Image Technique (DIT). The DIT capture photographic images at successive intervals of time which were fed through an image processing code to convert them to hue-saturation-intensity (HSI) format with the help of Surfer and Matlab computer softwares. Subsequently, PetraSim computer software was applied to predict the velocity behavior. The predicted velocity value shows that the laterite soil is compatible with the leachate and can be used as soil liner. The outcome of this study would enable designers to use non-destructive method to monitor and predict leachate migration in compacted soil liners to simulates leachate migration in waste containment applications.

The Influence of Compaction Effort in Laterite Soil with the Appearance of Sodium Bentonite as a Soil Liner

Soil liner which is placed at the foundation of a landfill is very important in order to isolate waste materials and leachate from the environment. However, if not properly managed, the leachate can beriskytothe safety and serviceability of which are directly related to the environment and public health issues. Soil liners were proposed to minimize leachate egress and prevent ground pollution. In soil liner design, it is important to compact the layer properly in order to achieve low hydraulic conductivity and high strength of soil. In this study, different percentages of sodium bentonite were added to laterite soil to act as soil liner to stabilize the liner system. Sodium bentonite can easily absorb water more than a hundred percent of its weight. Thus, the sodium bentonites were chosen to be mixed with laterite soil. The differentpercentagesof sodium bentonite used are 5%, 10%, 15% and 20%. This research was carried out asan attempt to see the compaction effort for laterite soil mixedwith sodium bentonite. The outcomesof this study give positive results due to the potential of sodium bentonite to fulfill spaces in between soil particles. It is also found that sodium bentonite influences the resistance properties, hydraulic conductivity and the strength of soil.

A method to assess risk reduction when utilizing geosynthetic clay liners (GCLs) with compacted soil liners

This paper presents an analytical solution developed to estimate probabilities of “failure” or advective flux “exceedance” for the case of a spatially variable geosynthetic clay liner (GCL) situated over a spatially variable compacted soil liner (CSL). The risk of utilizing such a liner system is assessed relative to a regulatory compacted clay-based soil liner. The analytical solution developed is validated over a range of parameters against random field simulation using the Local Average Subdivision method, and the analytical solution is shown to be in good agreement with simulation. The analytical solution is then used to examine the “probability of exceedance” for a spatially variable GCL and CSL combined liner system. It is shown that the use of a GCL can potentially result in a low probability of exceedance when used with a spatially varying, high hydraulic conductivity CSL. The risk of exceedance generally decreases as the hydraulic conductivity of the CSL decreases. An example problem is presented to demonstrate the capabilities of the analytical solution.