U.S.-Japan Cooperative Science: Use of Reinforcement-Drainage Geosynthetics in Embankment/Wall Construction with Marginal Backfill

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0355430HanThis award supports a three-year international collaborative research project between Professor Jie Han at Widener University in Chester, Pennsylvania, Professor Dov Leshchinsky at the University of Delaware and Professor J. C. Chai at Saga University in Japan. They will undertake a study on the use of reinforcement-drainage geosynthetics in embankment/wall construction with marginal backfill. Geosynthetics have been successfully used as one or a combination of the following functions: reinforcement, drainage, separation, filtration, and/or containment in earth structures. In current embankment/wall construction, geosynthetics have been mostly used as reinforcement for the stability of embankments/walls. Current specifications require the use of high-quality, free-draining, granular backfill for constructing mechanically stabilized earth (MSE) retaining walls. However, marginal backfill including cohesive backfill has been increasingly used to construct embankments/walls due to economic and availability constraints. Many studies have indicated that an increase of fine-grained particles in backfill would make the backfill more susceptible to moisture/water. The detrimental effects of water in the backfill are to reduce strength and modulus, increase deformations (including creep deformation), and destabilize earth structures by increasing earth pressures and inducing seepage forces. When marginal backfill is used, use of geosynthetics for drainage as well as reinforcement becomes critical to the performance of embankments/walls. The researchers will be studying the following areas: 1) the drainage behavior of the geosynthetics, especially the long-term transmissivity of geosynthetics confined in marginal soil; 2) the consolidation behavior of marginal soil between layers of geosynthetics; 3) the interaction behavior between geosynthetics and marginal soil including direct sliding and pullout; and 4) the stability of embankments/walls using geosynthetic reinforcement with or without a drainage function. The project brings together the efforts of laboratories that have complementary expertise and research capabilities. The research will have an impact on the use of reinforcement-drainage geosynthetics in embankment/wall construction with marginal soil and provide guidance for the design of earth structures using these dual function geosynthetics. The project advances international human resources through the participation of a postdoc and a number of undergraduate students. Through the exchange of ideas and technology, this project will broaden our base of basic knowledge and promote international understanding and cooperation. Results of the research will be disseminated at scientific meetings and in scientific journals. The research will also be made available on the Internet.