Mechanical Characterisation of Unsaturated Sandy Subgrades Based on Suction-Controlled Repeated Load Triaxial Testing

What is the topic of your Doctoral Thesis?

My thesis deals with better understanding the permanent deformation in roads originating in the subgrade, which is the foundation of a pavement structure.

Why did you choose this topic?

As an Industrial PhD, the project’s topic was already chosen. On the other hand, starting a project with a predefined set of objectives is challenging and required some adjustments along the way. I applied for this project because I had just finished a masters in Road Engineering and was intrigued with the project’s objectives.

What are the most important results?

As natural occurring materials, subgrades can have its mechanical properties changed by nature and by human action. The intertwined succession of events changing its properties is something challenging to simulate in the lab, but that was my quest. The most important results stem from the nature-induced change in humidity in the subgrade which in its turn develops suction in the soil, making it stiffer and more resistant to plastic deformations. This nature-induced change in humidity is connected to human action on the ground, so to say, how much load have been applied to this body mass composing the subgrade which has possibly changed its structure for good.

Who will benefit from your results? What kind the impact may it have on surrounding society?

By shedding light into the subgrade behaviour to loading under different environment conditions, I hope it will be of use to enhance pavement design solutions. The results constitute one more building block in the body of knowledge contributing to a so-called mechanistic-empirical pavement design approach. With the results from my study, pavement responses to traffic loading can be better predicted using realistic mechanical properties of some sandy subgrades. Most importantly, the test procedure that I came up with can be replicate to expand the database containing subgrade mechanical properties.

What will you do next?

I will be working as a pavement engineer in a leading consulting engineer firm.