Swelling and collapse behavior of unsaturated expansive subgrades stabilized with recycled glass

The swelling and collapse behaviors of expansive soils cause significant damage to light infrastructures such as pavements. This study investigates the swell-collapse behavior of expansive clay subgrade improved using recycled glass (RG) under unsaturated conditions. First, the optimum recycled glass content (ORGC) was determined based on the reduction in swelling potential. Next, static compaction tests were carried out on clay specimens stabilized at ORGC to establish a constitutive surface, namely virgin compaction surface (VCS) that exhibited the relationship between the moisture, stress and deformation states. The capability of the VCS in interpreting the swell-collapse responses was evaluated by applying various state paths. One-dimensional compression tests were conducted on specimens to investigate the mechanisms of swelling and collapse under a range of moisture contents and stress levels. Findings showed that the specimens’ behavior at ORGC = 25 % followed the developed VCS during loading, unloading and wetting paths, except those prepared at low moisture contents and wetted under low stresses. Utilizing the volume change data, a prediction model was developed and validated to estimate the swelling and collapse potential at ORGC. The proposed model provides a practical methodology to predict the volume change response of mixtures of fine and granular pavement materials through unsaturated soil theory.