Semi-automatic Mobile System for Detecting Defects in Landfill Liners: Tests in a Pilot Plant at LNEC

Abstract

The effectiveness of lining systems in service conditions is highly dependent on the performance of geomembranes. However, defects are every-present problem, and for covered geomembranes such as the ones used in landfills, it seems that most defects appear during the placement of the granular material that forms the Primary Leachate Collection System (PLCS). Although some test methods detect and locate defects in geomembrane liners after the placement of the PLCS, they are time consuming and quite expensive. Also, they were mainly developed for simple liner systems consisting of a geomembrane placed over a Compacted Clay Liner (CCL) and, in Portugal, the municipal solid waste landfill liner systems typically consist of a geomembrane placed over a Geosynthetic Clay Liner (GCL), over a CCL. In addition, existing methods were not developed for double liner systems such as the ones generally used in hazardous landfills. A research program aimed at developing a prompt and accurate test method to check geomembrane integrity is in progress. A semi-automatic mobile prototype equipped to record data on the location of defects has been tested in both small and large scale pilot plants. The aim of first pilot plant was to study the resolution and accuracy of the prototype and its response to the water content of materials in contact with the geomembrane. The second pilot plant, constructed at Laboratório Nacional de Engenharia Civil, I.P. (LNEC) campus, has been used to study the aptness of the prototype to detect and locate defects in different types of liner systems (simple and double). This paper focuses on the tests carried out at the second pilot plant. Results obtained suggest that the prototype is able to detect and locate defects in different types of liner systems