Date of Award

Spring 5-15-2022

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Advisor(s)

Negussey, Dawit

Keywords

EPS Geofoam, Non destructive testing, Optic sensors, Poisson's ratio, Shear modulus, Young's modulus

Subject Categories

Civil and Environmental Engineering | Civil Engineering | Engineering

Abstract

Models using EPS geofoam rely on input elastic parameters derived from compression tests on small size samples. Young's modulus and Poisson's ratio are parameters required to model isotropic and homogenous material behavior. For the most widely used EPS density grade of 20 Kg/m3 (1.25 pcf), Young's modulus of 4 MPa and Poisson's ratio of 0.1 are commonly used. Use of these values in models led to unreasonable long term deformation predictions that contradicted with field observations. Tests on small samples are prone to edge effects. Edge effects in turn result in underestimation of input elastic parameters. Alternative tests and sensing systems were utilized in this investigation to provide Young's modulus and Poisson's ratio values for EPS densities. Higher moduli for EPS densities were obtained from flexure, nondestructive (ND) and bender element (BE) tests. ND and BE tests also produced higher Poisson's ratio values based on observations of P and S wave velocities. Compression tests under lateral deformation restraint, with observation of lateral deformations using proximity transducers as well as detection of hoop strains with fiber optic sensors resulted in higher Poisson's ratio values. Young's modulus and Poisson's ratio derived from this investigation are more than twice the values obtained from compression tests on small samples. Sensitivity analysis was performed using a pavement model overlying an EPS geofoam layer under traffic loading. FLAC, SIGMA/W, and KENLAYER models with higher EPS Young's modulus and Poisson's ratio values resulted in better agreement with field observations and realistic service life predictions. Alternative tests and sensing systems utilized in this investigation provided input parameters that represent field performance of full-sized EPS blocks in geotechnical applications.

Access

Open Access

Download

Share

COinS