Shear strength characteristics and static response of sand-tire crumb mixtures for seismic isolation

Abstract

The objective of this study is to investigate the shear strength characteristics, energy absorption capacity and brittleness index of sand-tire crumb mixtures using simple direct shear test and Unconsolidated Undrained (UU) triaxial test for the effective use of waste tire crumbs for seismic isolation of building. Tire crumbs were prepared with special machinery where scrap tires were crushed into pieces and powders after removal of steel belting. The processed tire crumbs obtained from local industry were sieved into four size groups, i.e. 8 mm - 5.6 mm, 5.6 mm - 4.75 mm, 4.75 mm - 2 mm, and 2 mm - 1 mm and relatively uniform sand has been selected to generate sand-tire crumb mixtures (STCM). Grouped tire crumbs are mixed with sand to generate STCM samples having 0%, 10%, 15%, 20%, 25%, and 30% tire crumbs by volume. Direct shear and UU triaxial compression tests have been carried out on STCM samples for different normal and confining pressure with constant density of 1.54 g/cc. Stress-strain curves obtained from UU test for different confine pressure have been used to estimate energy absorption capacity by measuring area of stress-strain curve up to strain level of 20% for different size and percentage of tire crumbs. The experimental results show that the parameters controlling shear strength, energy absorption and stiffness are tire crumb size, percentage of crumbs, normal stress and confining pressure. Peak strength was significantly increased by adding rubber with sand. It is found that peak strength, energy absorption and stiffness increases with increasing percentage of tire crumbs up to 25%. Among tests of different tire crumb sizes, 5.60 mm gives maximum efficiency than other crumb sizes.