Erosion protection for slopes at ONGC Uran, Maharashtra
|Client||L & T Hydrocarbon (Construction & Pipelines)|
|Application||Erosion protection on slopes|
|System offered||StrataWeb® geocells filled with concrete and vegetated soil|
|Project execution||March 2013|
The construction giant L&T ECC Construction Group (Hydrocarbons Division) was setting up an additional process unit for ONGC at Uran, about 50km from Mumbai across the Harbour on the West Coast of Maharashtra, India.
The terrain and the process required terracing. Terracing would be natural as well as constructed and the surfaces of the slopes would require protection against erosion.
SGIPL was appointed by L&T to provide a solution for slope protection as well as development of greenery where possible. A technically viable and economic solution was to protect the slopes with StrataWeb® geocell in-filled with local soil which is vegetated.
Apart from these requirements, there were strict deadlines to complete the design, supply and execution within six weeks.
Within the hydrocarbon process area, vegetation would tend to dry and become a fire hazard; in such cases plain cement concrete infill was recommended. Slopes were of varying angles and appropriate StrataWeb® types were selected.
Where vegetated soil infill was required, the StrataWeb® SW71 panel size was 8.9m x 5.0m. Where concrete infilling was required, smaller panels SW35 of size 2.59m X 5.6m were preferred.
The placement procedure was as follows:
The existing slope surfaces were dressed and loose material was removed before laying StrataWeb®. The shorter sides of the panels were placed along the shoulder of the slopes. Galvanised steel spikes of 8 mm ɸ and 400mm length were used at suitable spacing both horizontally and vertically to anchor StrataWeb® to the base soil slope. To take care of the balance downward forces, high strength polymer tendons were interwoven with StrataWeb® to transfer the balance sliding force to an anchor trench at the top.
At respective designated locations, local soil and M15 lean concrete were placed. The materials within the geocells were tamped manually. The concrete in-fill was cured with sprinkled water. Where greenery was proposed, grass mats were placed over StrataWeb® with soil in-fill, which were periodically watered for almost a month to foster greenery.
Benefits to Clients
- Fast mobilisation and ease of start-up.
- No skilled labour required
- Advantage of using locally available material for in-fill
- Rapid installation on relatively steep slopes which otherwise would not be possible with traditional methods.
- Thinner section in case of concrete, thereby prevent cracking and also saving costs
- Virtually zero maintenance in case of concrete infill and minimum maintenance in case of green slopes.
- Approximate saving of 15% over traditional methods.
- Lower carbon foot print