Introduction

Civil engineering application is a growing market for scrap tires. Scrap tires have been successfully used as light-weight fill [5]; [9]; [7], insulation beneath roads [6], light-weight backfill for retaining walls [9], overlay of underground ramps or storage space [4], and as stream crossing [2], primarily because of low unit weight, high permeability and good insulating properties.

The placement and compaction of tire shreds leads to a layered, anisotropic material behavior. Isotropic deformability parameters and time-dependent creep behavior of tire-shreds were reported in the past by several researchers [5]; [6]; [9]; [3]; however, only a few studies have been carried out to evaluate anisotropic properties of a tire shred model. Heimdahl and Drescher (1999) first attempted to develop an elastic anisotropic model for tire shred behavior using a biaxial testing apparatus. They reported over a dozen plane stress tests at two loading conditions and averaged the elastic constants thus determined. A large variation of in-plane Poisson's ratio was reported with the possibility of negative values discussed. The authors acknowledged that the test apparatus employed was not the best for determining Poisson's ratio.

This paper deals with the development of an elastic-plastic material model for the tire shred material. In particular, our aim was to use a large scale triaxial testing apparatus, developed at University of California, Davis to calibrate the elastic and elastic-plastic material model for anisotropic material. Our immediate goal was to create, verify and validate an elastic-plastic material model that can then be used in numerical assessment of seismic behavior of bridge abutments. The validation procedure will ultimately include computational and experimental simulations of two bridge abutments made of tire shreds, performed using a large centrifuge facility at UC Davis.