Projects

Background

Roads stretch across thousands of kilometres and encounter complicated traffic/environmental loads in various climatic, hydrological and geological conditions. Unbound pavement materials, which provide support to the surfacing and distribute the loads to the subgrades, are susceptible to moisture degradation from exposure to water infiltration and evaporation in the natural environment. Cyclic and impact loads generated by moving traffic on the moisture-weakened Unbound pavement materials causes breakage and damages that can result safety concerns and frequent road maintenance.

The current design standards for unbound pavement materials are based on elasticity and experience, and do not consider the degradation of the pavement materials under moisture and traffic loads. In general, the hydro-mechanical behaviour of unbound pavement materials is complicated when it is subjected to long-term traffic loads and climate effects. Changes in water content and suction, mainly caused by evaporation and infiltration, alter almost all the engineering properties of an unbound pavement material, such as strength, deformability, water/air permeability and heat diffusivity. The situation becomes more complex when the unbound pavement materials are working under traffic loads which feature a combination of cyclic loads and rotation of principal stresses.

The proposed project aims to understand the hydromechanical behaviour of unsaturated unbound pavement materials under cyclic loads and transportation loads through advanced laboratory testing. The key factors that affect the hydromechanical behaviour of unsaturated unbound pavement materials will be identified and employed to develop a practical constitutive model for unbound pavement materials used in road construction and pavement engineering.

Project Objectives

1. To undertake a review of hydromechanical behaviour for unbound pavement material, testing methods, and modelling framework under cyclic loading, and climatic effects.

2. To develop an experimental approach for testing hydromechanical behaviour of unsaturated unbound pavement material under cyclic loads and transportation loads.

3. To identify the key factors that affects the hydromechanical behaviour of unsaturated unbound pavement material under cyclic loads and transportation loads.

4. To develop a practical constitutive model for describing the hydromechanical behaviour of unsaturated unbound pavement material under cyclic loads and transportation loads.

5. To validate the proposed model via experimental results under various loading and climate scenarios.