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Performance And Behaviour Of Coir Geocell Systems For Soil Stabilisation And Erosion Control

MERZ Geo Cells are three-dimensional, honeycomb-shaped cellular structures that create a strong confinement system when filled with compacted soil or other materials. This system effectively controls erosion caused by surface run-off and sheet flow, providing slope stability that is not possible with traditional two-dimensional solutions. The confined infill forms a stable surface layer that resists sliding, while each cell acts as a small micro-climate zone supporting vegetation growth and soil health.

Coir Geocell, made from natural coir fibre, is an eco-friendly and cost-effective solution for soil reinforcement. It strengthens soft or weak soils by providing all-round confinement, preventing lateral movement under load. This improves the soil’s strength, stiffness, and long-term durability, making Coir Geocell an excellent choice for sustainable ground improvement and erosion control applications.

A number of research and experimental studies carried out by the product manufacturer in India have evaluated the mechanical performance of Coir Geocell systems under various loading and environmental conditions. These investigations examined their use in slope stabilisation, erosion control, and seismic liquefaction resistance.

SLOPE STABILISATION AND EROSION CONTROL

Laboratory and model-scale experiments demonstrated that Coir Geocells provide strong lateral confinement to soil, significantly improving slope integrity under rainfall and hydraulic stress. When used together with vegetative mulch (such as wheat straw), the system supports both structural stability and vegetation growth by retaining surface moisture and reducing run-off.

Twelve physical slope models were tested to assess the combined influence of rainfall intensity, slope gradient, and cell size on soil displacement and erosion. Key findings included:

• Enhanced erosion resistance: Slopes reinforced with Coir Geocells maintained cohesion even under heavy rainfall, while unreinforced slopes suffered cracking and slippage.
• Reduced soil movement: Under moderate rainfall (≈ 50 mm/h), erosion was limited to less than 40 grams, compared with more than 4 000 grams under extreme rainfall (≈ 100 mm/h).
• Improved confinement efficiency: Smaller cell sizes (≈ 200 mm) reduced slope displacement by 10–25 mm compared with larger cells, confirming that smaller cells provide greater stiffness and stability.
• Effect of slope gradient: Steeper slopes experienced greater erosion and displacement, but geocell confinement mitigated these effects, distributing stresses more evenly through the slope.

The results confirm that Coir Geocells improve slope performance by providing load distribution, reducing lateral soil movement, and maintaining integrity during high-intensity rainfall. Combined with vegetative cover, they form an effective, environmentally friendly solution for slope and embankment protection.

MECHANICAL BEHAVIOUR AND STRUCTURAL MODELLING

A separate analytical study the structural behaviour of Coir Geocell-reinforced slopes using a beam-based modelling approach. The geocell layer was treated as a flexible slab foundation capable of carrying both bending and membrane stresses.

The study incorporated key parameters such as geocell thickness, placement depth, layer spacing, and soil shear strength. The findings demonstrated that:

• The Coir Geocell acts as a broad, flexible slab that redistributes stresses and limits potential failure planes within the slope.
• The system mobilises both tensile and bending actions, resulting in greater slope stiffness and reduced deformation.
• The optimal position of the geocell layer is between the mid-height of the slope and the mid-depth of the critical failure surface.
• Interface friction between the coir material and the surrounding soil contributes significantly to load transfer and confinement efficiency.

This research highlights that the three-dimensional confinement of Coir Geocells provides structural behaviour similar to a reinforced slab—enhancing overall slope stability and reducing lateral displacement compared with conventional two-dimensional reinforcement systems. 

LIQUEFACTION RESISTANCE IN COASTAL SAND

Another experimental programme investigated the influence of Coir Geocells on soil liquefaction behaviour in coastal sandy soils. Using laminar box shake-table tests to simulate earthquake conditions, saturated sand beds with 30% relative density were reinforced with Coir Geocell layers placed at various depths.

Key observations included:

• Coir Geocell reinforcement reduced excess pore-water pressure generation during shaking, lowering the risk of liquefaction.
• The full-height (200 mm) Coir Geocell configuration provided the greatest improvement, increasing liquefaction resistance by approximately 44.5 %.
• Confinement from the geocell limited lateral soil movement, enhanced interlocking of sand particles, and improved cyclic performance.
• The natural tensile strength of coir fibre contributed to stress redistribution and better energy dissipation during dynamic loading.

These findings confirm that Coir Geocell reinforcement is an effective and sustainable method for improving the seismic and dynamic stability of loose, saturated sands in coastal or earthquake-prone areas.

KEY INSIGHTS AND ENGINEERING IMPLICATIONS

Across all studies, Coir Geocells consistently demonstrated the following benefits:

• Enhanced mechanical performance: Increased shear strength, stiffness, and load-bearing capacity.
• Improved erosion and deformation control: Effective in steep slopes and high-rainfall conditions.
• Structural versatility: Capable of mobilising bending, tensile, and membrane actions for broad stress distribution.
• Hydrological stability: Supports drainage and reduces pore pressure build-up.
• Environmental compatibility: Biodegradable, supports vegetation, and provides a low-carbon alternative to synthetic materials.

These outcomes confirm Coir Geocells as a viable natural geotechnical reinforcement for use in slope protection, embankments, road bases, and coastal ground improvement applications.

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