Geotextile vs. Geomembrane: Functions, Differences & When They Are Used Together

A geotextile is a permeable textile, with polyester filaments laid into a loose web and needled together, and twelve grades cover 125 g/m² to 800 g/m² on 6 m rolls.

The geomembrane is an extruded polymer sheet at 0.940 g/cm³ and up, from 1.0 mm to 3.0 mm thick, and the fabric filters, drains and cushions while the sheet holds permeability below 1×10⁻⁷ cm/s.

Seams and stone punctures are where membranes fail, and slipping overlaps plus clogged pores are where fabric fails, since a seam passes at 0.25 MPa for 5 min while an overlap under 150 mm opens as the sheet unrolls. A defect shows up as a leak in the first wet season.

Fifteen hectares of landfill cell carry 150,000 m² of base liner, and an 8 m × 140 m roll of 1.5 mm sheet gives 1,120 m² at 1.58 t, so the job needs 134 rolls and 212 t across 8 containers. The 600 g/m² cushion adds 90 t.

Regulation sets a floor, and 40 CFR 258.40 asks for 30 mil of membrane over 2 ft of compacted soil while our release thresholds run tighter at 2,000 h of stress-crack resistance plus ±3% on thickness^[1].

A 1.5 mm sheet with a 600 g/m² cushion takes 1.41 t of resin and 0.6 t of fabric per 1,000 m², a ratio of 2.4 to 1, and a 50-year buried life works out at 0.028 kg of resin per square metre each year.

What each material does

Water passes through a PET non-woven geotextile by design, and a 600 g/m² grade moves 30 L/s/m² under a 50 mm head with an apparent opening size O90 between 0.06 mm and 0.11 mm.

Drainage measures 20 L/s/m² at the heavy end against 100 L/s/m² at the light end under a 50 mm head, reinforcement carries 9.5 kN/m to 45 kN/m across the grade range, and cushioning absorbs 1,500 N to 10,000 N of CBR puncture on a 50 mm probe.

An HDPE geomembrane wants the opposite result, and a 1.5 mm sheet has no pore size to quote, so the material and the welds are the two barriers while our line holds thickness inside ±3% against the ±10% GRI-GM13 allows.

40 CFR 258.40(b) defines a composite liner as a system consisting of two components. The upper component must consist of a minimum 30-mil flexible membrane liner, and the lower component must consist of at least a two-foot layer of compacted soil with a hydraulic conductivity of no more than 1 × 10⁻⁷ cm/sec. FML components consisting of high density polyethylene (HDPE) shall be at least 60-mil thick, and the FML component must be installed in direct and uniform contact with the compacted soil component^[1].

A 600 g/m² fabric measures 4.4 mm thick, and reversing the Darcy equation gives an equivalent conductivity of 2.6×10⁻¹ cm/s against a 1×10⁻⁷ cm/s limit on the soil below.

Six orders of magnitude separate those two figures, and thickness does nothing to close the gap.

Puncture resistance behaves differently, since a 1.0 mm sheet and a 2.0 mm sheet show no measurable difference in transmission and the heavier grade reaches 1,000 N of index puncture against 700 N.

Some duties belong to the sheet alone, since biogas covers normally use 1.0 mm to 1.5 mm of LLDPE, waste capping normally uses 1.0 mm to 2.0 mm, and root barriers start at 2.0 mm.

The cushion grade follows the stone size under the liner. Send the share of stones above 25 mm, the slope ratio and the sheet thickness, and we return a 600 g/m² or 800 g/m² pairing with the mass per 1,000 m².Send the parameters

Testing methods stay separate

A 9.5 kN/m result from D4595 and a 16 kN/m result from D6693 get compared all the time, and the two numbers come from different methods with different definitions^[2][3].

Tensile strength on a sheet splits into yield and break, and a 1.5 mm polyethylene sheet reports 24 kN/m at yield against 40 kN/m at break, so printing one figure for both is an error.

Paperwork follows the same split, with a fabric certificate carrying D4632 grab tensile, D6241 puncture and D4491 permittivity while membrane certificates carry two tensile figures from D6693 plus an ESCR count from D5397.

Interface shear is the one method both families share, and the test pairs layers exactly as they will be built, with a textured surface pushing interface friction to 30° across a 2:1 slope.

The numbers side by side

The fabric range splits into 12 grades from 125 g/m² to 800 g/m², and tensile runs 9.5 kN/m at the light end against 45 kN/m at the heavy end, a spread of 4.7 times.

Thickness splits the sheet range in 0.5 mm steps from 1.0 mm to 3.0 mm, and index puncture climbs from 330 N to 1,000 N across that range, a spread of 3 times.

Ageing decides how long a sheet lasts, and GRI-GM13 sets a floor of 100 min standard OIT plus 400 min high-pressure OIT with 55% retention after 90 days at 85 °C^[13] while our line releases at 2,000 h of stress-crack resistance.

Thickness units cause trouble on membrane orders, since one mil equals 0.0254 mm and 60 mil comes to 1.52 mm against 59.1 mil for 1.5 mm, a 0.02 mm gap that sits inside the ±3% D5199 allows, and the nonwoven geotextile data sheet lists roll length against every fabric grade.

1 t trial orders and 7 to 15 day lead times

Inside a composite liner

Fabric goes under the sheet in every composite build, since some subgrades carry a bottom liner layer sequence into the design, and compacted soil keeps sharp stones at the surface and the point load a 1.5 mm sheet takes from a 25 mm stone runs far above its 550 N index puncture value.

The cushion mass follows the grade, since a 300 g/m² fabric puts 0.3 t into every 1,000 m², a 600 g/m² grade puts in 0.6 t and a 1,000 g/m² grade puts in 1 t, and that depth of fibre is what a cushion that stops stone puncture relies on.

A double liner runs the pair twice with a leak detection layer between them, and that arrangement comes to seven layers in total.

40 CFR 264.301(c) requires the lower component to be built from at least 3 feet (91 cm) of compacted soil with a hydraulic conductivity of no more than 1 × 10⁻⁷ cm/sec. The leak detection system stands on a drainage layer with a conductivity of 1 × 10⁻² cm/sec or more and a thickness of 12 inches (30.5 cm) or more^[15].

A single-layer base liner runs through 6 steps, and two of them carry the risk, since density below 90% lets the subgrade settle after the sheet goes down while an overlap under 150 mm opens as the sheet is unrolled.

1. Subgrade compacted above 90% with stones larger than 25 mm stripped out.
2. The 600 g/m² fabric laid as the cushion with 150 mm overlaps.
3. A 1.5 mm sheet unrolled down the slope with 1.5% slack for thermal movement.
4. Seams run 25 mm wide as dual-track wedge welds across 100 mm to 150 mm overlaps.
5. Every seam air-tested at 0.25 MPa for 5 min with no pressure drop.
6. A second 600 g/m² fabric over the sheet before the drainage gravel goes down.

When the two go in together

Canal linings invert the order, so the concrete slab sits on top with the fabric and the sheet below it, and Giroud and co-authors documented a built section of 1.5 mm sheet on 500 g/m² polypropylene needle-punched fabric^[16].

Shotcrete surfaces carry the same problem for tunnels, since a membrane pressed onto rough concrete gets punched by the high spots, and fabric of 400 g/m² to 600 g/m² cushions the sheet while draining the seepage behind it.

Several jobs need only one of the two, and road separation, retaining wall drainage and sports field trenches take 200 g/m² to 500 g/m² of fabric on their own, which reaches 0.2 t to 0.5 t per 1,000 m².

Thin sheets cause the opposite failure, since membranes of 0.2 mm to 0.5 mm used in canals from the 1950s onward showed a large number of holes shortly after installation^[16], and half a millimetre is the whole problem.

Choosing weight and thickness

Weight follows the function, and fibre source and production control decide how repeatable a grade stays, while French drains plus retaining wall filter layers take 100 g/m² to 200 g/m² with the filter cloth AOS selection deciding the fine end of that range.

Cushioning sets the highest bar, since a 600 g/m² grade reaches 7,500 N of CBR puncture and an 800 g/m² grade reaches 10,000 N, which puts 0.6 t and 0.8 t into every 1,000 m².

Sheet thickness follows head and load, so a 5 m column of fresh water puts 49 kPa on the sheet while a 10 m column puts 98 kPa, roughly 0.98 bar.

• Light cover and garden ponds take 1.0 mm sheet over 300 g/m² fabric.
• Canals and reservoirs take 1.5 mm sheet over 500 g/m² fabric.
• Municipal landfill base liners take 1.5 mm sheet over 600 g/m² fabric.
• Heap leach pads and tailings take 2.0 mm sheet over 800 g/m² fabric.
• Hazardous waste double liners take 1.5 mm to 2.0 mm sheet over 600 g/m² to 800 g/m² fabric.
• Slopes of 2:1 favour a textured liner surface that reaches 30° of interface friction.

A woven and non-woven geotextile comparison settles fabric type before weight, and the cushion layer almost always lands on the non-woven side for its filtration and drainage behaviour.

What to check on delivery

Fabric rolls and membrane rolls get inspected on different lists, and a 200 g/m² roll should read about 220 m against 75 m at 600 g/m², with any net mass off the label by more than 2% going back on the scale.

Membrane rolls carry thickness, width, length and batch with one certificate per roll, and thickness gets read as a 10-point average from D5199, so a mismatched batch label stops the delivery.

Both products want shade, since fabric UV stabilisers keep more than 75% of strength after 500 h and membrane retention from D7238 stays above 60% at 1,600 h, and our batch test documentation travels with every order.

Every roll leaves the plant with a batch certificate covering D5397 stress cracking, D5885 high-pressure OIT, ±3% thickness and D4632 grab tensile.See the release tests

What to put in the order

A membrane quote turns on 4 items, which are thickness, roll width, destination port and application, while fabric quotes turn on 3, which are weight, roll width and roll length.

• Product and surface, smooth or double-textured, with texture for 2:1 and steeper.
• Specification, written as 1.5 mm thickness or 600 g/m² weight.
• Sheet size, for example 8 m × 140 m.
• Quantity, with trial orders from 1 t to 3 t and export orders from one 40HQ container.
• Destination port and application, since heap leach pads take 2.0 mm and fish ponds take 1.0 mm to 1.5 mm of food-grade LLDPE.
• Lead time, at 7 to 15 days for standard grades and 15 to 25 days for custom or mixed loads.

One 40HQ container takes about 15 to 17 rolls of 8 m membrane or about 38 to 39 rolls of fabric, and the lighter 200 g/m² grade comes to 50,000 m² against 17,000 m² at 600 g/m².

A geotextile quantity for tunnel linings calculation follows the same logic, the mil versus mm thickness guide covers the conversion end to end, and the landfill liner system package bundles sheet, GCL and fabric against one specification.

One 40HQ container holds 15 to 17 membrane rolls or 38 to 39 rolls of 200 g/m² fabric. Thickness, weight, roll width and destination port turn that into a quote.Price by container Read the FAQ

Data sources

Official figures and published data carry a superscript at the end of the sentence, and they cover the GRI-GM13 and GRI-GM17 specifications, the ASTM test methods, 40 CFR 258.40 and 264.301, GB 16889-2008^[17] and the Giroud canal lining paper, which between them supply every limit quoted here.

Items marked typically follow common industry practice without a traceable source, and subgrade compaction at 90%, overlaps of 100 mm to 150 mm plus a welding window of 200 °C to 350 °C all sit in that group.

Remaining figures are calculated inside this article, where one mil converts at 0.0254 mm and sheet mass uses a polymer density of 0.94 kg/L.

Container arithmetic starts at 8 m × 140 m for 1,120 m² and 1.58 t per roll, while the 4.4 mm fabric under a 50 mm head at a gradient of 11.4 yields 2.6×10⁻¹ cm/s through Darcy’s law.

Sources

1. U.S. Electronic Code of Federal Regulations. Title 40, Section 258.40: Design criteria for municipal solid waste landfill units. www.ecfr.gov
2. ASTM International. ASTM D4595/D4595M: Standard Test Method for Tensile Properties of Geotextiles by the Wide-Width Strip Method. www.astm.org
3. ASTM International. ASTM D6693/D6693M: Standard Test Method for Determining Tensile Properties of Nonreinforced Polyethylene and Nonreinforced Flexible Polypropylene Geomembranes. www.astm.org
4. ASTM International. ASTM D4632/D4632M: Standard Test Method for Grab Breaking Load and Elongation of Geotextiles. www.astm.org
5. ASTM International. ASTM D6241: Standard Test Method for Measuring Static Puncture Strength of Geotextiles and Geotextile-Related Products Using a 50-mm Probe. www.astm.org
6. ASTM International. ASTM D4833/D4833M: Standard Test Method for Index Puncture Resistance of Geomembranes and Related Products. www.astm.org
7. ASTM International. ASTM D4751: Standard Test Methods for Determining Apparent Opening Size of a Geotextile. www.astm.org
8. ASTM International. ASTM D4491/D4491M: Standard Test Methods for Water Permeability of Geotextiles by Permittivity. www.astm.org
9. ASTM International. ASTM D5199: Standard Test Methods for Measuring the Nominal Thickness of Geosynthetics. www.astm.org
10. ASTM International. ASTM D5321/D5321M: Standard Test Method for Determining the Shear Strength of Soil-Geosynthetic and Geosynthetic-Geosynthetic Interfaces by Direct Shear. www.astm.org
11. ASTM International. ASTM D8117: Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by Thermogravimetric Analysis. www.astm.org
12. ASTM International. ASTM D5885/D5885M: Standard Test Method for Oxidative Induction Time of Polyolefin Geosynthetics by High-Pressure Differential Scanning Calorimetry. www.astm.org
13. Geosynthetic Institute. GRI Test Method GM13: Standard Specification for Test Methods, Test Properties and Testing Frequency for High Density Polyethylene (HDPE) Smooth and Textured Geomembranes. geosynthetic-institute.org
14. ASTM International. ASTM D5397: Standard Test Method for Evaluation of Stress Crack Resistance of Polyolefin Geomembranes Using Notched Constant Tensile Load Test. www.astm.org
15. U.S. Electronic Code of Federal Regulations. Title 40, Section 264.301: Design and operating requirements for hazardous waste landfills (double liner, 3-foot compacted soil at no more than 1 x 10-7 cm/sec, leak detection layer with 1 percent bottom slope). www.ecfr.gov
16. Giroud J.P., Plusquellec H., Blond E. Design of canals lined with geomembranes. E3S Web of Conferences 368, 01001 (2023). doi.org
17. Ministry of Ecology and Environment of the People’s Republic of China. GB 16889-2008 Standard for pollution control on the landfill site of municipal solid waste (compacted clay below the liner at 0.75 m or more, natural foundation layer at 2 m or more, hydraulic conductivity below 1.0 x 10-7 cm/s) [in Chinese]. www.mee.gov.cn