Numerical Modelling of the Assembly of Big Bags to Optimize Landfill Disposal

The so-called ‘big bags’ are used in landfills to dispose waste material in a sequential manner. In this study, big bags are constituted by geosynthetics and filled with organic waste similar to granular material. The result is an element having a blocky shape and being highly deformable. The process of deployment of big bags for waste disposal in landfills becomes crucial when considering the stability of these assemblies. This paper is intended to focus on the understanding of the mechanisms governing the stability of these assemblies of blocks by means of Distinct Element numerical modelling. To determine the appropriate properties to be assigned to the model, a calibration process was performed by simulating the behaviour of a single big bag undergoing loading and unloading stages. A real scale experimental setup was implemented at the site to test the behaviour of the block by superimposing a concrete cubic weight to a big-bag and measuring the deformations at different time intervals during loading and unloading. The numerical analyses showed to be appropriate to reproduce the behaviour of the big bag at the single block scale and were adopted to study the stability of the assembly in a variety of geometrical layouts. The work performed allowed the definition of the arrangement that guarantees the stability conditions of the assembly.