Geotechnical study of sand-fadr mixture for landfill cover and liner

Abstract EN

Engineering of waste containment facilities began in the 1970s with the introduction of clay liners and covers, which led to the sanitary landfills concept.

Currently, all waste landfill systems should have covers and liners of low permeability.

Consequently, the cover and liner design has undergone great changes, with new materials being introduced and new design philosophies being adopted.

The main and most important component of landfill cover and liner is the hydraulic barrier layer.

As clay is not readily available at many locations, different substitutions have been investigated.

One of these substitutions is the sand-bentonite mixture, which achieves good performance but with relatively high cost.

In this paper a new economical substitution is studied.

It consists of using fatty acid distillation residuals (FADR) mixed with sand as a hydraulic barrier layer.

Mixing sand with an appropriate percentage of FADR yields a mixture having low hydraulic conductivity that can be used as a hydraulic barrier layer in landfill liner and cover.

In this study, direct shear and hydraulic conductivity tests have been conducted on samples with different sand to FADR ratios to get the optimum value fulfilling the landfill liner and cover requirements.

The tests show that the minimum FADR percentage that achieves the required permeability suitable for most landfills is 4%.

In this case the mixture possesses a permeability k = 1 * 10-7 cm / sec, a cohesion c = 0.12 kg / cm2, and an angle of shearing resistance ø = 33.8°.

The research results indicate that the use of FADR in landfills is promising and can constitute a good landfill cover and liner alternative from the economical and technical points of view.