- Use of Wicking Fabric to Dehydrate Road Embankment under Unsaturated Conditions
- Duckering 535
Dr. Xiong Zhang
- Department of Civil and Environmental Engineering
- University of Alaska Fairbanks
When an infrastructure is built, for example, a pavement structure, it is often built with soils compacted at their optimum moisture contents. The surface soils are exposed to the surrounding atmospheric environment with relative humidity of less than 90%. Such a relative humidity corresponds to a suction value of 140 MPa. All soils become air-dry under such high suction and have very low permeability (nearly impermeable) to transport water from inside to outside. In the meantime, the soils inside the pavement structure tend to reach equilibrium with the ground water table through capillary rise. When surface soils are air-dry and have cracks, they have high permeability for water infiltration. As a result, the soils inside the pavement structure are often wet or have tendency to become wet with time. Increase in soil moisture content often means deteriorating performance. Research indicates when moisture contents of the soil increase from 3.3% to 6%, the resilient moduli for Alaska D-1 materials are at least reduced 50%. Therefore keeping moisture content low in the pavement structure is very important for pavement performance. Conventional drainage system relies on gravity to drain water out of soils, which cannot help prevent the above scenarios from happening. A new type of wicking fabric is recently developed to drain the water under unsaturated conditions and potentially maintain good performance. By installing a layer of wicking fabric in the pavement, the water in the pavement structure can be transported along the wicking fabric to the shoulder and vaporized to the surrounding atmosphere which has much higher suction. It is likely to generate a relatively dry zone in the pavement structure which not only can help improve pavement structure, but also help prevent the frost heave and subsequent thaw-weakening in cold regions. This seminar discusses the application of the wicking fabric to prevent the frost heave and thaw-weakening at the Beaver Slide of the Dalton Highway by dehydrating the water in the pavement structure under unsaturated conditions.
Dr. Xiong Zhang joined the faculty of the Department of Civil and Environmental Engineering at the University of Alaska Fairbanks in August 2006. He received his Ph.D. degree in Civil Engineering from the Texas A&M University, his B.S. and M.S. degrees from Tongji University in Shanghai, China and China Institute of Water Resources & Hydropower Research (IWHR), Beijing, China, respectively. Prior joining to the University of Alaska Fairbanks, he was a postdoctoral researcher and research associate at the Texas A&M University and Louisiana Transportation Research Center, respectively. Over the past eight years, he has secured over 2.5 million dollars of research funding to support his research activities. Dr. Zhang has published more than 50 journal and conference papers. He is a committee member of several nationwide technical committees such as TRB AFP60 Committee on Engineering Behavior of Unsaturated Soils, TRB AFS20 Committee on Soil and Rock Instrumentation, and ASCE Geo-Institute Pavement Committee and Shallow Foundation Committee. He is registered as a Professional Engineer in Alaska.