Case Study: Preventing Landslides in Nanded, Maharashtra with Ocean HDPE Liner – 1000 Micron

At an infrastructure site in Nanded, Maharashtra, heavy monsoon rain and saturated soil were making slopes progressively less stable. Ocean Non Wovens supplied 14,000 SQM of Ocean HDPE Liner – 1000 Micron and supervised its installation across the critical slope areas, using the liner as a barrier that keeps rainwater from soaking into the slope.

Rain-triggered slope failure is a national problem: the Geological Survey of India and NDMA estimate that about 12.6% of India’s land area (excluding snow-covered ground) is prone to landslides. Most of it lies in the Himalaya and the Western Ghats, but cut slopes and embankments anywhere can fail once water builds up inside them.

The problem: water in the slopes

Nanded sits on the Deccan basalt plateau, where weathered basalt (murrum) and clay-rich black soils lose strength quickly when saturated. Cut slopes and embankments for roads and development zones are the vulnerable points.

Before the work, the site had experienced:

• Surface erosion during the monsoon
• Rising pore water pressure because of poor drainage
• Progressive failure of slope toes, leading to slip surfaces

Vegetation planting and terracing had already been tried and failed: the rain was too intense and roots did not reach deep enough to hold the soil.

Why an HDPE liner

An HDPE geomembrane is an unusual choice for slope work, but the mechanism is simple. When rainwater infiltrates a slope, pore water pressure rises and the effective stress holding soil grains together falls, so the soil’s shear strength drops until the slope slips. Keep the water out and that trigger is removed. In Nanded the 1000 micron liner acted as a barrier over the slope, shedding rainwater to the drains instead of letting it percolate in.

• Puncture resistance: stands up to sharp rock edges and minor soil movement.
• Low permeability: minimises infiltration into the slope, keeping pore water pressure down.
• UV stability: carbon-black stabilised for long-term performance in exposed conditions.
• Chemical resistance: unaffected by acidic rainfall or contaminated soil.

One design check matters on slopes: a smooth HDPE sheet has relatively low friction against soil and geotextile, so the slope angle and anchorage must keep the liner (and any cover placed on it) from sliding. Interface friction is measured by direct shear testing to ASTM D5321, and textured sheets are used where slopes are steep.

Installation

1. Slope assessment and grading: a geotechnical survey mapped the unstable zones, and slopes were graded to a stable angle for liner placement.
2. Subgrade preparation: fine grading and compaction removed voids, and a non-woven geotextile (150 GSM) was laid as a cushion to protect the HDPE liner.
3. Liner deployment: the 1000 micron liner was rolled out with tension-controlled equipment and the panels joined by thermal fusion welding into a continuous, leak-free sheet.
4. Anchorage and drainage: anchor trenches were excavated and backfilled to stop the liner moving, and French drains and HDPE drainage pipes were installed to carry away the runoff the liner sheds.

After installation, Ocean’s site team ran a thermographic scan of the welds as an additional check on seam quality, alongside the usual air-pressure and vacuum-box tests used on geomembrane seams. The system stabilised the slopes without major changes to the landscape.

What the liner changes

• Infiltration control from day one: vegetation takes years to stabilise a slope; the liner controls seepage and surface erosion as soon as it is welded and anchored.
• Lower pore water pressure: less water entering the slope means less loss of shear strength during heavy rain.
• Less erosion: rain runs off the sheet into the drains instead of washing soil off the face.
• Lower cost than structural options: a lined and drained slope is usually cheaper to build than a retaining wall over the same length.

About Ocean Non Wovens

Ocean Non Wovens supplies HDPE geomembranes and other geosynthetics for slope protection, landfill lining and water containment. For slopes that need erosion protection rather than a waterproof barrier, see also our erosion control mats. Get in touch to discuss your project.