Manual Geotextile Apparent Opening Size (AOS) Tester – QualiGTX™ AOS M
The QualiGTX™ AOS M determines the apparent opening size of single-layer geotextiles and related geosynthetic
materials through dry sieving with graded glass beads. Its manually operated controls regulate a motor-driven sieve
shaker, allowing laboratories to obtain O95 measurements without the setup and maintenance associated with
programmable interfaces. Designed for woven, nonwoven, and composite geotextiles, the instrument supports material
evaluation across commercially available fabric constructions. Manufacturers, contractors, quality-control
departments, and independent testing laboratories rely on these measurements to assess whether a geotextile's pore
structure is appropriate for the soil it must retain.
The instrument accommodates five specimens during a single testing cycle. Individual pressing rings secure each
fabric within the sieve column, while five stainless steel sieve pans collect the glass beads passing through the
respective specimens. A graded glass bead set is included, providing the reference material required for testing.
The 200 mm sieve column supports a total stack height of 400 mm, providing sufficient capacity for all five specimen
frames and collection pans in one operation. This multi-specimen arrangement allows laboratories to evaluate five
fabrics simultaneously rather than conducting separate tests for each sample.
The shaker operates with specified agitation rates and defined tolerances to maintain consistent testing conditions.
Its sieve base produces 220 oscillations per minute (±10) and 150 vertical impacts per minute (±10), with a 10 mm
amplitude and 12 mm radius of gyration. These operating limits provide measurable reference points for checking
equipment performance during commissioning and routine verification against the applicable test method. With an
overall weight of 80 kg, the instrument offers a practical configuration for standard laboratory workspaces.
Manual Geotextile Apparent Opening Size (AOS) Tester – QualiGTX™ AOS M Applications
The apparent opening size of a geotextile determines how effectively it can retain soil particles while allowing
water to pass through. Measuring this property helps engineers and material specialists select appropriate fabrics
for separation, filtration, drainage, and erosion-control applications.
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Incoming Geotextile Quality Inspection: Evaluates incoming fabric batches against the manufacturer's declared
O95 value, helping quality-control personnel identify materials that do not meet specified requirements
before installation.
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Road and Railway Subgrade Stabilization: Assesses separation geotextiles used between subgrade soils and
aggregate base layers, ensuring the fabric can restrict the upward migration of fine particles under
repeated traffic loads.
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Subsurface Drainage Systems: Provides the opening size data needed to select compatible filter fabrics for
trench drainage, roadway edge drains, and collector pipe installations.
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Dams, Canals, and Hydraulic Structures: Evaluates filtration materials placed behind riprap, beneath
revetments, and around toe drains to support soil retention in dams, levees, and canal protection systems.
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Coastal Protection and Slope Erosion Control: Determines the suitability of geotextiles used in scour
protection aprons, gabion linings, and silt fences before deployment in exposed environments.
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Landfill and Waste Containment Applications: Verifies the pore characteristics of filtration and protective
geotextile layers incorporated into leachate collection arrangements and landfill cover systems.
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Third-Party Material Testing: Performs routine apparent opening size assessments for independent laboratories
supporting engineering specifications, regulatory agencies, and product certification programs.
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Geotextile Product Development: Helps manufacturers examine how fiber diameter, needling density, and
calendering conditions influence the resulting pore structure, supporting product comparisons and material
development.
Manual Geotextile Apparent Opening Size (AOS) Tester – QualiGTX™ AOS M Key Features
The QualiGTX™ AOS M combines direct manual controls, five-specimen testing capacity, and controlled mechanical
agitation in a configuration designed for dry sieving applications.
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Direct Manual Controls: Provides straightforward operation through dedicated controls rather than
software-driven menus, simplifying operator training and eliminating software maintenance requirements.
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Motorized Sieve Shaker: Uses a 0.37 kW motor to generate consistent oscillating and tapping movements
throughout the test cycle, providing controlled mechanical agitation instead of manual shaking.
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Five-Specimen Testing Capacity: Allows five geotextile samples to undergo testing in the same cycle, reducing
the time required for batch inspection and routine laboratory work.
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Five Stainless Steel Collection Pans: Separates the beads passing through each specimen for individual
weighing while providing corrosion resistance during cleaning and routine handling.
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Five Specimen Pressing Rings: Secures each fabric flat within its respective frame without introducing
tension, helping maintain consistent conditions across all five specimens.
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Complete Graded Glass Bead Set: Includes the reference beads required for apparent opening size measurements,
allowing laboratories to begin testing without sourcing a separate bead set.
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200 mm Sieve Column and 400 mm Stack Height: Provides room for the complete arrangement of specimen frames
and collection pans, allowing all five samples to be processed in one cycle.
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Defined Agitation Tolerances: Maintains an oscillation rate of 220 cycles per minute (±10) and a tapping rate
of 150 impacts per minute (±10), supporting consistent test conditions between operators and laboratories.
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Controlled Motion Geometry: Combines a 10 mm amplitude with a 12 mm radius of gyration to establish the
prescribed movement pattern and distribute glass beads across the specimen surface.
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80 kg Compact Construction: Offers a manageable equipment footprint for conventional laboratory layouts and
makes repositioning between workbenches easier than with heavier sieve-shaking equipment.
Theory and Test Method
The dry sieving method determines the apparent opening size of a geotextile by evaluating how glass beads of known
sizes pass through its structure. Rather than measuring individual pores directly, the procedure establishes a
relationship between bead diameter and the proportion passing through the fabric.
Testing begins by securing a geotextile specimen in a sieve frame and placing a weighed quantity of glass beads from
a narrowly graded size fraction on its surface. The shaker then agitates the assembly for the specified testing
period. Beads smaller than the openings they encounter can pass through the fabric and collect in the sieve pan
below. The collected material is subsequently weighed to establish the percentage of the original bead charge that
passed through the specimen.
The procedure is repeated using progressively larger bead fractions to generate a series of passing percentages.
These measurements are plotted against the corresponding bead diameters to establish a particle-size distribution
curve. The apparent opening size, designated O95, is determined at the diameter corresponding to 5% passing or less.
This value represents an approximate upper particle-size threshold for material passing through the geotextile.
O95 is an important consideration when selecting filtration fabrics. An opening size that is too large can allow soil
fines to migrate through the geotextile, potentially compromising the stability of the surrounding structure.
Conversely, openings that are too small can become blocked by retained particles, restricting water movement and
reducing drainage performance.
The mechanical action of the sieve shaker plays a critical role in obtaining reliable measurements. Horizontal
circular oscillation moves the glass bead layer across the specimen, exposing the beads to a representative
distribution of fabric openings rather than concentrating contact in one area. Vertical tapping provides additional
impact energy, helping dislodge beads that become temporarily lodged within the fiber network.
Both movements must remain within their specified operating ranges because variations in oscillation and tapping
rates alter the energy transferred to the bead layer. These changes can affect bead passage and shift the resulting
apparent opening size. The QualiGTX™ AOS M maintains controlled agitation through its defined operating tolerances,
supporting repeatable testing conditions and comparable O95 measurements.
Manual Geotextile Apparent Opening Size (AOS) Tester - QualiGTX™ AOS M Technical Specifications
| Parameter |
Specification |
| Test Principle |
Dry sieving, single-layer geotextile and related products |
| Measured Property |
Apparent opening size (AOS / O95) |
| Sieve Diameter |
200 mm |
| Sieve Stack Height |
400 mm |
| Sieve Base Amplitude |
10 mm ± 2 mm |
| Sieve Oscillation Rate |
220 oscillations/min ± 10 |
| Tapping Rate |
150 taps/min ± 10 |
| Radius of Gyration |
12 mm ± 1 mm |
| Specimen Capacity |
5 specimens per cycle |
| Control Type |
Manual |
| Motor Power |
0.37 kW |
| Votlage |
380 V |
| Dimensions (W × D × H) |
770 × 650 × 1060 mm |
| Weight |
80 kg |
Included Configuration
| Item |
Quantity |
Description |
| Standard Glass Bead Set |
1 set |
Graded reference beads for dry sieving determinations |
| Specimen Pressing Rings |
5 |
Clamps geotextile specimens flat within the sieve frames |
| Stainless Steel Sieve Pans |
5 |
Collects beads passing through each specimen for individual weighing |
| Sieve Column Assembly |
1 |
200 mm frames with 400 mm stacking capacity |
