Abstract:
The presence of weak subgrades is one of the greatest challenges in
constructing road pavements. Conventionally, techniques such as refiling with suitable
material and soil stabilisation are considered to improve subgrade condition,
ignoring the additional project cost. However, geogrids have gained popularity as
economical, expedite and sustainable subgrade improvement techniques over recent
times. Although many studies have been conducted to assess the suitability of
biaxial geogrids, limited studies have been performed to check the suitability of
composite geogrids for subgrade improvement, despite assuming that composite
geogrids extend additional benefits. In this study, two model tests: one unreinforced
and one composite geogrid reinforced, were constructed in a steel box with length,
width, and height of 1 m, 1 m and 1.2 m, respectively. The subgrade was prepared to
a thickness of 500 mm, achieving CBR 2.5% bearing capacity. A granular layer
of 200 mm was constructed on top of the subgrade achieving 100% degree of
compaction frommaximum dry density. In the reinforced section, composite geogrid
was placed at the base subgrade interface. Both model sections were subjected to a
monotonic load at a rate of 1 mm/min, applied on the top surface of the granular layer
through a circular plate of 200 mm diameter, until the occurrence of ultimate failure.
Results demonstrate that reinforcing the weak subgrade by a composite geogrid
has increased the ultimate bearing capacity by 53%. In addition, the overall section
modulus of the composite geogrid reinforced section is higher than the modulus of
the unreinforced section.
