Mechanical Behaviour of a Clay Layer for Landfill Cap Cover Application: Experimental Investigation and Numerical Modelling

Summary

Dedicated hazardous waste landfills have a cover barrier including, in particular, a compacted clay liner, which is a major element of the safety of the site. However, the implementation of this barrier poses many problems, in particular in terms of compaction. Moreover this cover must keep its sealing function during the lifetime of the landfill and the period of waste monitoring. However, potential differential settlements within the waste should be considered and this phenomenon can induce bending strains in the clay layer and create damage. Four point bending tests are performed in the laboratory to characterise the clay behaviour. Analysis is focused on the crack initiation and on the consequences of damage (crack propagation) on the mechanical behaviour. In addition a numerical simulation, by the discrete elements method, was carried out on the same type of tests. The comparison between the results from the numerical modelling and those from the experimental tests provides a method to determine the mechanical parameters of the material. These results are used to optimise the method of implementation of the clay on site and also to predict the mechanical behaviour of the material.