Projects

Roads stretch across thousands of kilometres and encounter complicated traffic/environmental loads in various climatic, hydrological and geological conditions. Subgrade soils, which provide support to the pavements, are susceptible to moisture degradation due to exposure to water infiltration and evaporation in the natural environment, specifically in areas where the subgrade soil comprises expansive soils or collapsible soils sensitive to moisture. Cyclic and impact loads generated by moving traffic on the moisture-weakened subgrade soils cause damage that can result in safety concerns and increased road maintenance.

The current design standards for the subgrade are generally based on elasticity and experience, and do not consider the degradation of the subgrade soils under moisture and traffic loads. In general, the hydro-mechanical behaviour of subgrade soils 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 a subgrade soil, such as strength, deformability, water/air permeability and heat diffusivity. The situation becomes more complex when the subgrade soil is 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 subgrade soil under cyclic loads and transportation loads through advanced laboratory testing. The key factors that affect the hydromechanical behaviour of unsaturated subgrade soil will be identified and employed to develop a practical constitutive model for road construction and pavement engineering.

1. To undertake a review of unsaturated subgrade behaviour, testing methods, and modelling framework under cyclic loading, and climatic effects.

2. To develop an experimental approach for testing hydromechanical behaviour of unsaturated subgrade soil under cyclic loads and transportation loads.

3. To identify the key factors that affect the hydromechanical behaviour of unsaturated subgrade soil under cyclic loads and transportation loads.

4. To establish practical constitutive model to describe the hydromechanical behaviour of unsaturated subgrade soil under cyclic loads and transportation loads.

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