Standard 25 mm
Pneumatic Vice Action Grip
Pneumatic vice action grips clamp the full specimen width at a constant, even pressure — which is what stops one side slipping or tearing before the other.
SpecificationsTesting standard
ISO 10319
Geosynthetics — Wide-width tensile test
Written and technically reviewed by Dak System Inc. engineeringLast reviewed
ISO 10319 is the wide-width tensile test for geosynthetics. The specimen is 200 mm wide and shorter than it is wide, because a narrow strip of geotextile contracts as it is pulled and reads far below the material's real capability. Results are reported as force per unit width, not as stress.
At a glance
- Test type
- Tensile — the specimen is pulled apart
- Published by
- ISO
- Edition
- ISO 10319:2015
- Runs on
- Series 7200 and Series 9000
What the test does
A strip of geosynthetic 200 mm wide, and shorter along the pull than it is wide, is clamped across its full width and extended at a rate expressed as a percentage of gauge length per minute until it fails. Force is recorded against strain measured on the specimen itself. From the curve come three reported values: the maximum load per unit width in kilonewtons per metre, the strain at that maximum, and the secant stiffness at whatever strain the specification names. Procedures for both conditioned and wet specimens are included, and the machine and cross-machine directions are tested separately.
What it measures, and why it matters
The load a geosynthetic can carry per metre of width, and how much it stretches getting there — which is what reinforcement design actually consumes. A reinforced soil wall or an embankment over soft ground is designed around force per metre and a stiffness at working strain, not around a stress, so the method reports in the units the designer uses. The standard describes itself as an index test: it gives design parameters and a basis for acceptance under controlled conditions, and does not model the interaction between the geosynthetic and the soil around it.
Why wide, and why short
The specimen is wider than its gauge length on purpose. That is the entire reason the method exists.
- Width
- 200 mm nominalWide enough that the centre of the specimen cannot contract inwards as it stretches.
- Gauge length
- Shorter than the widthThe unusual aspect ratio is deliberate, not a compromise for grip space.
- Reported as
- Force per unit width, kN/mNot stress. Geotextile thickness is compressible and not a meaningful denominator.
- Wet testing
- A defined procedure is includedMany geosynthetics work permanently saturated, and some lose strength when wet.
- Geogrids
- Applicable, with specimen dimensions adjustedA grid has to be cut on whole ribs and junctions, so 200 mm is a target rather than a rule.
- Not applicable to polymeric or bituminous barriers
- Applicable to clay barriers
It is an index test by its own description. It gives design parameters for reinforcement and a basis for acceptance, and it is not a model of soil interaction.
Test speed
- Rate
- A percentage of gauge length per minuteA rate in mm/min alone is meaningless when gauge lengths differ between products.
- Reported
- Maximum load per unit width, strain at maximum load, secant stiffness
- Strain measurement
- On the specimen, not from crosshead travelOn a short gauge length, grip take-up and slippage swamp the real extension.
- Test machine and cross-machine directions separately
- DakReinforcement geotextiles are usually strongly directional by design.
Calculations
Tensile strength per unit widthTmax
Tmax = Fmax / B
- Fmax
- maximum force, kN
- B
- nominal specimen width, m
Force per metre of width. Reinforcement design works in these units directly, which is why nothing is divided by a thickness.
Strain at maximum loadεmax
εmax = (ΔL / L₀) × 100
- ΔL
- extension at maximum load
- L₀
- gauge length
Measured on the specimen. Crosshead travel includes grip take-up, which is a large fraction of a short gauge length.
Secant stiffnessJ
J = T / ε at a specified strain
- T
- tensile force per unit width at that strain
- ε
- the specified strain, as a fraction
Quoted at a stated strain — commonly 2 % or 5 % — and the strain must be stated with the value or the number means nothing.
How the test runs
- 01Cut specimens 200 mm wide in the machine and cross-machine directions.
- 02For geogrids, cut on whole ribs and junctions and adjust dimensions accordingly.
- 03Condition the specimens, or saturate them where wet properties are required.
- 04Fit wide-width grips, using a roller or capstan arrangement for high-strength products.
- 05Clamp the full width evenly and check the specimen is square to the load.
- 06Fit an extensometer to the specimen for strain.
- 07Set the rate as a percentage of gauge length per minute.
- 08Load to failure, recording force and strain.
- 09Calculate maximum load per unit width and strain at maximum load.
- 10Calculate secant stiffness at the strains the specification requires.
- 11Reject any specimen that failed at or in the jaws, and report the two directions separately.
The fixture this method needs
What the report has to contain
- Reference to ISO 10319 and the edition
- Product identification, type and mass per unit area
- Direction tested and specimen dimensions used
- Whether specimens were conditioned or tested wet
- Grip type and clamping arrangement
- Rate of extension as a percentage of gauge length
- Maximum load per unit width, and strain at maximum load
- Secant stiffness with the strain it was evaluated at
- How strain was measured
- Number of specimens rejected for jaw failure
What the machine must be capable of
Capacity that follows the product — a reinforcement geogrid can exceed a hundred kilonewtons per metre, so the frame is sized for the strongest item in the range. Grips must hold the full 200 mm width evenly, and for high-strength products a roller or capstan arrangement is effectively required, because a flat jaw clamped hard enough to hold the load will crush the fibres at the jaw line and cause the specimen to fail there. Strain must be measured on the specimen, since on a short gauge length grip take-up is a large fraction of crosshead travel.
What goes wrong in practice
Taking strain from the crosshead, which overstates elongation and understates stiffness by a margin that grows as the gauge length shrinks. Quoting a secant stiffness without the strain it was evaluated at, which makes the figure unusable rather than merely incomplete. Accepting jaw breaks into the data set, where they always read low. And testing only dry specimens for a product that will spend its service life saturated, when the standard supplies a wet procedure precisely because some materials lose strength when wet.
ISO 10319 or ASTM D4595
| ISO 10319 | ASTM D4595/D4595M | |
|---|---|---|
| Family | ISO | ASTM |
| Specimen | 200 mm wide, short gauge | 200 mm wide, comparable aspect |
| Reported | kN/m and secant stiffness | Force per unit width and modulus |
| Wet procedure | Included | Addressed in the method |
Very close in principle, and both exist for the same reason — a narrow strip reads low. Cite the one the specification names, since geosynthetic acceptance documents are written against a particular designation.
Questions we are asked about this test
What is ISO 10319?
It is the wide-width tensile test for geosynthetics — an index method covering woven and nonwoven geotextiles, geocomposites, knitted geotextiles, geonets, geomats and metallic products, and applicable to geogrids with adjusted specimen dimensions. It measures the load-elongation behaviour of a 200 mm wide strip and reports maximum load per unit width, strain at maximum load and secant stiffness.
Why does the specimen have to be so wide?
Because a narrow strip of geotextile contracts inwards as it is stretched. The yarns at the edges pull towards the centre, the specimen waists, and the recorded strength falls well below what the material would deliver in the ground where it is continuous in every direction. Making the specimen 200 mm wide and shorter than it is wide prevents that contraction, which is why the aspect ratio looks wrong and is deliberate.
Why is the result in kN/m rather than MPa?
Because geotextile thickness is not a meaningful denominator. A nonwoven compresses substantially under the pressure used to measure it, so any stress calculated from it would depend on how hard the gauge was pressed. Reinforcement design also works directly in force per metre of width — that is the quantity a retaining wall or a reinforced embankment is designed with — so normalising by width rather than area matches both the measurement and the use.
Why must strain be measured on the specimen?
Because the gauge length is short and grip take-up is not. When the specimen is only around 100 mm between clamps, the settling of the fabric in the jaws and any slippage represent a large fraction of the total crosshead movement. Strain calculated from crosshead travel therefore overstates elongation substantially and understates stiffness, which matters because secant stiffness at a stated strain is one of the primary reported values.
What is secant stiffness and why is the strain always quoted with it?
It is the tensile force per unit width divided by the strain, evaluated at a specified strain — commonly 2 % or 5 %. Because a geosynthetic's load-strain curve is not straight, the value depends entirely on where it is taken. A stiffness quoted without the strain it belongs to is not an incomplete number, it is an unusable one, and specifications always name the strain.
Why does the standard include a wet procedure?
Because many geosynthetics spend their whole service life saturated, buried in soil below the water table or in drainage applications, and some materials lose strength when wet. Testing only conditioned dry specimens would report a property the product never has in service. The method therefore defines how to saturate and test wet specimens so the difference can be quantified rather than assumed.
What if a specimen breaks in the jaws?
It is rejected. A break at the clamp line reports the damage done by the grips, not the strength of the fabric, and it always reads low. High-strength reinforcement products are particularly prone to it, which is why roller or capstan clamping is used for them — a flat jaw tight enough to hold the load will crush the fibres where it grips. A high rejection rate is a signal about the clamping, not the material.
Running ISO 10319 on the Series 7200 and Series 9000
Dak verifies against whichever standard the method names, and where a class applies our frames sit a class tighter than it asks.
| The method asks for | Dak supplies | |
|---|---|---|
| Capacity | Moderate to high — a reinforcement geogrid can exceed 100 kN/m, so frame capacity follows the product | Load cells from 1 kg to 60 ton on the Series 7200, and 0.5 to 100 kN on the Series 9000 |
| Force accuracy | ISO 7500-1 Class 1 over the working range | ISO 7500-1 Class 0.5 — a class tighter than the method asks |
| Strain measurement | An extensometer of the class the method specifies | Certified to ISO 9513 Class 1 and ASTM E83 — non-contact video, clip-on and high-elongation |
| Gripping | Wide-width grips clamping the full 200 mm specimen width, with roller or capstan clamping for high-strength products | Our eccentric roller grips or split capstan grips, built to the specimen |
| Environment | 23 ± 2 °C standard laboratory atmosphere | 3009 series chambers, −150 °C to +400 °C — temperature only |
This page describes the method as practised. The governing text is the current edition from the issuing body. Tell us what you are testing and we will answer with the machine, the fixture and a quotation.