Unbound geomaterials used in roadway base layers strongly influence pavement durability, yet current practices in Minnesota often focus narrowly on gradation and index properties. This research seeks to fill that gap by examining mechanical behavior alongside hydraulic, water retention, and suction characteristics to better understand how these materials perform within real-world environmental and pavement systems.

Pavement base layers serve two essential purposes: providing mechanical support that prevents fatigue, settlement, and rutting, and enabling drainage that protects the structure from elevated pore pressures and freeze‑thaw damage. Although millions of tons of these materials are used annually, past studies rarely consider the full interaction between the base layer, surface conditions, and environmental factors.

The project’s primary goal is to develop a new holistic guideline for selecting unbound geomaterials and designing pavement foundations. By integrating both mechanistic and hydraulic considerations, the long‑term objective is to support a shift toward design approaches that enhance roadway performance while reducing maintenance needs and costs.

The Objectives:

This project aims to develop a new holistic unbound geomaterial selection and pavement foundation design guideline. This will be achieved through the completion of four primary objectives:

1. Review of current roadway foundation design practices and guidelines of MnDOT and local counties and cities in Minnesota.
2. Collection and analysis of existing data from the literature on the topic (including the extensive previous work of the research team).
3. Developing a holistic design and material selection framework that explicitly takes material drainage characteristics, material mechanical characteristics, unsaturated soil mechanics properties, and prevailing environmental characteristics into account.
4. Extensive laboratory and field testing to demonstrate and verify the new approach.
5. Evaluating and modifying the pore suction resistance factors and seasonal multipliers used in MnPAVE.

Project Details:

• Estimated Start Date: 7/10/2025
• Estimated Completion Date: 6/30/2027
• Funding: MnDOT and Local Road Research Board
• Principal Investigator: Bora Cetin
• Co-Principal Investigators: Tuncer Edil, Michele Lanotte, and William J. Likos
• Technical Liaison: Ceren Aydin

Details of the research study work plan and timeline are subject to change.

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