Rapid Determination of Unsaturated Moisture Diffusivity for Soils During Frost Heave

AIDC project number: 510017

  • Rifat Bulut
  • Xiong Zhang
  • Gang Chen
  • AUTC
  • University of Alaska Fairbanks
  • Oklahoma Transportation Center
  • Start Date: Jul 1, 2011
  • End Date: Dec 31, 2012

Project Summary

Frost heave and thaw weakening are typical problems in northern regions. It is well known that frost heave is caused by water flow through capillary zone to a freezing front where it forms ice lenses. Investigation of soil behavior in the capillary zone is in the range of unsaturated soil mechanics and the unsaturated transmission of water is the key to understand the frost heave problem.

The magnitude and rate of transient moisture flow in an unsaturated soil in response to suction changes is controlled by the unsaturated moisture diffusion coefficient. It is well-known that unsaturated soil properties such as moisture diffusivity are significantly different from those when the soil is fully saturated with positive pore water pressure. Although significant progress has been made in unsaturated soil mechanics in the past two decades, not enough advancements have been made to apply this new field to practical, yet very important, problems such as the frost heave and thaw weakening problems.

As part of an Oklahoma Transportation Center (OkTC, one of the ten National University Transportation Centers) sponsored research project, Mabirizi and Bulut (2010) developed a unified, simple, and practical testing equipment and method to measure both the drying and wetting unsaturated soil moisture diffusivity coefficients in laboratory. Compared with the existing methods, the method significantly reduces the time and efforts for measuring the drying and wetting unsaturated soil moisture parameters by exposing the cylindrical soil specimens to drying and wetting cycles, respectively. The same concept can be applied to measuring the unsaturated diffusivity of soils during one dimensional frost heave in Alaska. The objective of this research is to implement the most recent advances made in unsaturated soil mechanics to investigate the frost heave problem. The objective will be achieved through equipment development, laboratory testing, model development, and numerical simulation.