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.