Choosing the wrong geotextile for your landfill is like hiring a flimsy security guard to protect a bank vault. A thin, weak fabric will tear, allowing a single sharp rock to puncture your expensive geomembrane, compromising the entire containment system.

For landfill applications, the most suitable specifications are for nonwoven, needle-punched geotextiles, typically made from polypropylene. The key is to match the weight and strength to the specific job: heavy grades (600–2,000 g/m²) for liner protection and lighter grades (200–400 g/m²) for filtration and separation.

As a geosynthetics supplier, I've seen projects suffer setbacks from specifying the wrong geotextile. It’s not just about picking a product; it’s about understanding the different jobs a geotextile does within a landfill. It acts as a bodyguard, a filter, and a separator, all at once. Getting the specification right for each of these roles is the difference between a system that lasts for 50 years and one that fails in five. Let's walk through exactly how to choose the right specs for your project.

What functional requirements guide the selection of geotextile specifications for landfill separation and filtration?

Many people think a geotextile is just a simple fabric layer. This mistake leads them to underestimate its role and select a cheap, inadequate product that puts the entire project at risk.

The selection is guided by four primary functions: protection of the geomembrane, filtration of leachate, separation of different soil or waste layers, and in-plane drainage to relieve water pressure.

Understanding these four functions is the first step to selecting the correct specification. Each function places a different demand on the fabric. In my experience, explaining these roles helps clients see why a one-size-fits-all approach doesn't work.

Function	What It Does	Why It's Critical in a Landfill
[Protection]	Acts as a thick cushion to shield the impermeable geomembrane from being punctured by sharp stones, gravel, or waste.	This is the most important function. A single puncture in the geomembrane can cause a catastrophic leak. The geotextile is the geomembrane's bodyguard.
[Filtration]	Allows water (leachate) to pass through freely while holding back fine soil or waste particles.	It prevents the leachate collection system (drainage pipes and gravel) from getting clogged with silt, which would cause leachate to build up and create immense pressure.
Separation	Keeps different material layers from mixing. For example, it prevents the aggregate of the drainage layer from mixing with the soft soil of the subgrade.	This preserves the integrity and function of each layer. Without separation, the drainage layer would lose its capacity and the subgrade could weaken.
Drainage	Transmits water within the plane of the fabric itself. This is a secondary function for thick nonwovens.	Helps relieve localized water pressure buildup, especially on slopes or behind retaining walls, contributing to overall stability.

How do key properties—such as tensile strength, permittivity, and puncture resistance—affect geotextile suitability?

A geotextile spec sheet can be confusing, full of technical terms and numbers. Focusing on the wrong property, like just tensile strength, can lead you to choose a product that looks strong on paper but fails in practice.

The most critical properties for landfill geotextiles are not tensile strength, but puncture resistance (CBR), thickness, and mass per unit area (g/m²). These directly relate to the fabric's ability to provide long-term protection.

When I review a spec for a landfill project, I look at these properties first. Tensile strength is important for reinforcement, but in a landfill, the geotextile's main job is to be a tough, durable cushion.

Property	Why It Matters for Landfills	Typical Specification
Mass per Unit Area (g/m²)	This is the weight of the fabric and is a primary indicator of its overall robustness, thickness, and protective capability. Heavier generally means tougher.	Protection: 600 - 2,000 g/m² Filtration/Separation: 200 - 400 g/m²
CBR Puncture Resistance (kN)	This measures the force required to push a plunger through the fabric. It directly simulates a sharp stone pressing against the geotextile. This is the single most important spec for protection.	Standard Protection: 3 - 5 kN High-Stress Protection: 5 - 8 kN
Thickness (mm)	A thicker fabric provides better cushioning, distributing point loads from sharp objects over a wider area. Thickness is more important than tensile strength for puncture protection.	Protection Layers: 4 - 8 mm (measured at 2 kPa)
Permittivity (sec⁻¹)	Measures how quickly water can pass through the fabric. It must be high enough to allow leachate to drain freely without building up pressure.	Must be much higher than the soil's permeability. Typically 0.05 - 0.1 l/m²·s for filtration.
Elongation (%)	The ability of the fabric to stretch before breaking. A high elongation (at least 50%) allows the geotextile to conform to ground settlement without rupturing.	A rigid, low-elongation fabric will tear under stress instead of stretching, offering poor protection.
Fiber Type	The raw material of the geotextile. Polypropylene (PP) is preferred over Polyester (PET) for most landfill applications due to its superior chemical resistance to acidic or alkaline leachate.	Choose Polypropylene (PP) for direct contact with waste. PET is suitable for other applications.

In which landfill zones are specific geotextile grades commonly applied?

A modern landfill is a complex system with different zones, each facing unique stresses. Using a super-heavy geotextile everywhere is wasteful, while using a light one in a high-stress area is dangerous.

The heaviest geotextiles (800-2,000 g/m²) are used to protect the geomembrane base liner. Medium-to-heavy grades (500-800 g/m²) are used on slopes, and lighter grades (200-400 g/m²) are used for filtration and in the final cover system.

Let's break down a typical landfill from the bottom up to see where each type of geotextile goes. As a supplier, this is the most common conversation I have with contractors and engineers.

1. Base Liner System (The Most Critical Area)
This is the "sandwich" at the very bottom of the landfill that contains all the leachate.

• Protection Layer (Above Geomembrane): This geotextile sits directly on top of the primary geomembrane and below the leachate collection gravel (and waste). It faces the highest puncture risk.
  • Specification: Use the heaviest grade. 800 g/m² to 2,000 g/m² nonwoven PP geotextile. A CBR puncture strength of >5 kN is essential.
• Cushion Layer (Below Geomembrane): This layer sits underneath the primary geomembrane, protecting it from the prepared subgrade or a secondary drainage layer.
  • Specification: A heavy grade is still needed. 400 g/m² to 800 g/m² is typical.

2. Leachate Collection & Drainage System
This includes the gravel blankets and pipes that collect leachate.

• Filtration Layer: The geotextile wraps around drainage pipes or separates the drainage gravel from soil. Its job is to let water in but keep fine soil out.
  • Specification: Focus on filtration properties. A lighter 200 g/m² to 400 g/m² nonwoven geotextile with the correct apparent opening size (AOS) is perfect.

3. Slope System
The side slopes of a landfill cell experience shear stress from the waste and require robust protection.

• Protection/Cushion Layer: This geotextile is placed directly against the geomembrane on the slope.
  • Specification: Needs a good balance of puncture resistance and thickness. Typically 500 g/m² to 800 g/m².

4. Final Cover System
This is the cap placed on top of the landfill once it is full.

• Separation/Filtration Layer: Here, the geotextile separates the topsoil layer (for vegetation) from the underlying drainage layer.
  • Specification: Stresses are lower here. A 200 g/m² to 500 g/m² geotextile is usually sufficient.

How can I match geotextile specifications to project design criteria to ensure long-term performance?

You now understand the functions, properties, and locations. The final step is putting it all together to create a purchase order that guarantees you get the right material for your specific landfill design.

First, identify the landfill zone. Second, determine the primary function (protection or filtration). Third, select the mass (g/m²) and puncture strength (CBR) based on the level of risk and stress in that zone.

Here is a practical table I provide to my clients to help them make the final selection. It connects the type of landfill and its location to a reliable specification.

Landfill Type & Location	Primary Function	Recommended Mass (g/m²)	Key Consideration
Small Municipal Landfill: Base Liner Protection	Protection	600 - 800 g/m²	Balance cost with a reliable level of puncture resistance (CBR > 4 kN).
Large/Permanent Landfill: Base Liner Protection	Protection	800 - 1,600 g/m²	Maximum puncture protection is non-negotiable. Use a thick, heavy-duty fabric.
Hazardous Waste Landfill: Base Liner Protection	Protection	1,200 - 2,000 g/m²	The absolute highest level of security is required. Use the thickest and strongest geotextile available.
All Landfills: Leachate System Filtration	Filtration	200 - 400 g/m²	Must have the correct opening size to prevent clogging. Permeability is more important than weight.
All Landfills: Slope Protection	Protection & Friction	500 - 800 g/m²	Needs to be strong enough to resist puncture and provide friction against the geomembrane to prevent sliding.
All Landfills: Final Cover	Separation & Filtration	300 - 500 g/m²	Must support vegetation and allow drainage without clogging the gas vent or drainage layer.

When you prepare your inquiry, come armed with this information. Tell your supplier: "I need a nonwoven polypropylene geotextile for primary liner protection in a large municipal landfill. The spec should be 1,200 g/m² with a CBR puncture resistance of at least 7 kN." A good supplier will immediately understand your needs and provide the right product to ensure your project's long-term success.

Zaključak

For landfill success, use heavy nonwoven geotextiles (600-2,000 g/m²) for liner protection and lighter grades (200-400 g/m²) for filtration. Matching the spec to the specific zone is critical.