Clogging potential of tire-shred drainage layer in landfill cover systems

Abstract

This paper investigates the clogging potential of shredded scrap tire drainage layers in landfill covers. Laboratory clogging tests were conducted using soil and shredded tire profiles in a large-scale permeameter. In each test, a layer of shredded tire overlain by a soil layer was subjected to flow under a constant hydraulic gradient condition. Two types of shredded tires were used for this study and they contained individual tire chips with sizes ranging from 2.5 cm to 50 cm. The soil layer consisted of silty clay that is commonly used as cover soil in landfill cover systems. Tests were also conducted by placing a geotextile filter between the soil and the shredded tire layers. During the testing, the outflow from the bottom of the shredded tire layer was measured. After a specified number of days, the inflow was stopped and the soil layer was removed. The soil was dried and weighed. If a geotextile was used, it was also removed, dried, and weighed. The mass of the soil that remained after completion of testing was compared with the initial mass of the soil used to determine the extent of soil infiltration into the underlying shredded tire layer. The hydraulic conductivity of the shredded tires was measured before and after soil infiltration. Overall, the test results showed that flow through the cover soil was very low, and the extent of soil infiltration into the shredded tires ranged from 4% to 15%, depending on the presence of a geotextile and the thickness of the soil layer. Despite partial clogging of tire-shred voids with the infiltrated soil, the hydraulic conductivity of the shredded tires still remained the same as the initial value of 3.5 cm/s to 6.5 cm/s demonstrating that shredded tires can be used as an effective drainage media in landfill cover systems.