Embankments are crucial to the construction of roads, railways, canals, earth dams and other storage utilities. When constructed in soft soils, ground improvement techniques are often used. Although many studies have demonstrated the suitability of geosynthetic reinforcements, very little information is available on geocell reinforced embankments. This has contributed to limited geocell use in stabilizing embankments and when utilized, it is often restricted to the transportation sector.
Case study – Red mud pond embankment, India
A study was carried out on a sample from Lanjighar, Orissa in India. The embankment was part of a red mud pond, used to store the red mud. Red mud is a waste product from the Bayer process of Alumina recovery. Due to capacity constraint, the embankment height needed to be raised.
Validation – Laboratory tests and analytical study
A laboratory study aimed to ascertain the suitability of the geocell foundation utilized in the embankment. NPA Geocells filled with dry sand were placed on a clay bed and compared to an unreinforced sample. Another sample was further reinforced with a biaxial geogrid. An incremental load was applied to strip footing placed along the width of a cast-iron test tank. The main results are summarized below.
- The NPA Geocell-reinforced sample recorded no clear bearing capacity failure, even up to the large settlement of 45% of footing width, while the unreinforced sample experienced distinct failure.
- Bearing capacity was increased in the NPA Geocell sample by 4 increments in comparison to the non-reinforced sample. When further reinforced by a basal geogrid, bearing capacity was increased to 5 increments.
- In the unreinforced sample, surface heaving was observed. In the case of the NPA Geocell reinforced sample and that further reinforced with a basal geogrid, no surface heaving was observed.
An analytical study showed that the combination of NPA Geocell and basal geogrid is beneficial. It not only mobilizes the additional strength in the clay bed but also resists the downward movement of soil due to the footing penetration.
Based on the experimental and analytical studies, the NPA Geocell foundation system was proposed to support the embankment, covering over 15,000 square meters of its base.
Benefits – Robust and cost effective
The newly constructed embankment on NPA Geocell foundation has sustained two monsoon rains and continues to function optimally. No cracks, seepage or settlements have been observed.
- Bearing capacity of the embankment foundation increased by 4-5 times
- Quick solution, with foundation work completed in just 15 days
- Locally available labor and tools used, significantly saving costs