Performance of tire chips–gravel combinations with nonwoven geotextile and encapsulated tire chips layers used as filter/separator under incremental stress levels

Abstract

High permeability of tire shreds/chips makes them suitable for many landfill applications but few concerns were raised by landfill designers/operators mainly related with excessive compressibility and higher clogging of tire shreds/chips. In this study, different sizes/shapes tire chips were assessed for their large-scale reutilisation (alone and in different combinations with gravel) without/with nonwoven geotextile used as filter/separator layer. The most appropriate tire chips size and shape (aspect ratio) was observed by considering changes in the axial strain and hydraulic conductivity response levels under increasing overburden pressure (stress) levels without/with geotextile use. Different sizes tire chips of the aspect ratio 1 to 4 were mixed with gravel in the mixing ratio’s of 75, 50 and 25%, (by weight) to get the proper combination with relatively lower compressibility and higher hydraulic conductivity without/with geotextile and without/with tire chips (TS1) cover layer used as filter/separator. Results clearly indicated that the TS1 size tire chips combination with gravel in the mixing ratio of ds : dg = 1 : 3 (in the encapsulated state between gravel and “small” size tire chips “cover” layer) performed better as the hydraulic conductivity reduction was comparatively lower even on higher stress levels. Small size “TS1” tire chips of aspect ratio 1 of 150–200 mm thickness layer used as replacement of geotextile in the landfill drainage system showed almost similar hydraulic conductivity performance and hence free drainage on relatively higher stress levels for longer duration under the anticipated worst case conditions. These experimental findings may enable the landfill designers/managers to reutilise the waste scrap tire chips on the large scale in a better manner.