Proposal of Xiaoming Yang of the
Development of a Mechanistic Response Model for Geocell Reinforced Aggregate Bases
Geocell is a three-dimensional honeycomb shaped geosynthetic. It is suitable for base reinforcement in paved and unpaved roads where geocell creates a reinforced mattress with unbounded base material. Compared to a 2-D geosynthetic product, such as geogrid and geoextile, geocell can provide better confinement to minimize soil particles from lateral movement. This confinement can result in a higher locked-in confining stress and thus a higher modulus of the base. Although experimental and field studies have demonstrated the favorable effects of geocell, its utilization has been greatly restricted due to the absence of a well-grounded design method. Researchers have been trying to develop mechanistic-empirical models for geogrid-reinforced bases that can be incorporated into the current Mechanistic-Empirical Pavement Design Guide (MEPDG). However, limited efforts have been made for geocell-reinforced bases partly due to the complexity of the 3-D problem.
The objective of this study is to develop a mechanistic response model that can simulate the confining effect of geocell under cyclic loading. This model will be based on the unreinforced response model developed in the NCHRP project 1-37a. New components to be incorporated include a non-linear elastic geocells model and an interface shear stress model. Initial tensile stress in the geocell due to compaction is also to be considered. This model will be calibrated using experimental data. A poorly-graded fine aggregate will be used as the base material in the experimental study. A three-dimensional finite difference software - FLAC3D will be used for the numerical study.
To achieve the above objective, the following tasks will be conducted in this study:
1) Conduct literature review about the development of current response models for unreinforced pavements in the current MEPDG;
2) Perform laboratory tests on aggregate and geocell materials to determine the parameters to be used in constitutive models;
3) Develop the numerical model with the above components. Incorporate constitutive models for aggregate and geocell and into the FLAC3D through computer programming;
4) Perform static and cyclic loading tests on geocell-reinforced bases in the laboratory to verify the numerical model;
5) Perform a parameter study on the effect of different properties of geocell, base, and subgrade.
6) Prepare a final report to summarize all the research findings.
Tasks 1 to 3, Tasks 4 to 5, and Task 6 will be completed in the first, second, and third years, respectively. This study will improve the understanding of the mechanism of geocell confinement for aggregate bases and develop a response model of geocellreinforced bases, which can be incorporated in the MEPDG. It will also promote the application of geocell products in transportation related projects.