Permanent Deformations Predictions of Unbound Base Materials Based on Results from a Testing Box Technique

Abstract

A test box method has been developed and used to analyse response and permanent
deformation characteristics of unbound granular materials. The box is 800 × 800 × 800 mm
and has been used to test two layered structures, an unbound base course layer over subbase,
totally 500 mm in high. The loaded area is in the centre of the box and consists of a circular
100 mm diameter plate. The response of the tested structure is measured with ten deformation
sensors located at two high levels. The instrumentation gives the possibility to study the load
spreading in the material due to applied vertical loading. Different applied load levels have
been used. Both the response measured as well as the development of the permanent
deformation have been modelled using the k-theta model for the measured resilient response
and three simple load hardening models have been used for permanent deformation. A set of
model parameters have been estimated that gave good agreement with the measurements.
These parameters are then used for verification of the test results with data from Heavy
Vehicle Simulator (HVS) - measurements.