Onsite Use of Recycled Asphalt Pavement Materials and Geocells to ...

dynamic deformation moduli from LWD tests, surface profiles before and after the tests, surface
permanent and elastic deformations at the center, permanent deformations of base and subgrade,
strains in geocell and pavement strain gauges, maximum vertical stresses at the interface between
subgrade and base, and stress distribution angles.
The applied load is distributed through the pavement structure to the subgrade. The stress
distribution angle method is a simple and approximate method to estimate the maximum stress at
the top of the subgrade. This method has been used by Giroud and Han (2004) to develop their
design method for geosynthetic-reinforced unpaved roads. The stress distribution angle from the
MA surface to the base course (α1) is generally higher than that from the base course to the
subgrade (α2) due to the higher modulus of the HMA surface as shown in figure 4.8. The earth
pressure cells at the interface between subgrade and RAP base measured the vertical stresses at
the bottom of the RAP base. The combined stress distribution angle (α) for the test section can be
calculated based on the vertical stress at the center as follows:
where,
P = applied load (40 kN);
P
2
p(
r h.
tan
)
(4.1)
p = vertical stress at the interface between subgrade and base course;
r = radius of the loading plate (15.2 cm in this study);
h = combined thickness of the HMA surface and RAP base;
α = combined stress distribution angle.
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