Cell integrity is dependent on the strength of the perforated strip and the weld (~90 degrees).
A tensile testing machine is used to determine the geocell tensile strength and seam weld strength. The strength of the weld on the strip must be equivalent or higher to the tensile strength of the strip itself.
Cell integrity is dependent on perforated strip strength
Strip Tensile Strength ISO 10319:2015 (Wide-Width)
The procedure utilizes a “wide-width” sample size, such that it includes a representative distribution of the strip wall perforations from seam to seam. (A ½ cell length can be used if the perforation pattern on each side is identical.)
A longitudinal force is applied to the test specimen at a constant strain rate at 100 mm/minute for load support applications – until the specimen ruptures. Measurement is performed by extensometer; tensile strength, strain at maximum load (in %) and stiffness are recorded and normalized for the thickness.
The test is carried out until the yield point, which indicates the geocell material strength
A longitudinal force is applied at 100 mm/minute until the specimen ruptures
PRS offers the highest strength tensile strength compared to any other geocell and is the only manufacturer to guarantee minimal tensile strength for perforated and non-perforated strips.
The following are the minimum geocell tensile strength values for categories B-D (±7%) according to ISO 10319:2015:
- Strength at Yield (non-perforated) (kN/m): from 21 to 25 kN/m (minimum value)
- Strength at Yield (perforated) (kN/m): from 16 to 22 kN/m (minimum value)
Seam Weld TENSILE Strength Test – ISO 13426-1 (Part 1 Method C)
Testing geocell seam weld strength is useful for quality control purposes. However, it is not a factor in engineering design, as the geocell strip will fail before ultrasonically welded seams, due to the perforations that weaken it.
A test of the geocell seam weld strength should reflect the 3D geometry of a geocell and its composite behavior as a mattress system in the field, not as an individual cell. Part 1 of the existing ISO standard lists four different geometries (A-D) for conducting the “weld strength” test. Method C – the SPLIT test – best simulates the geocell geometry at ~90° similar to an installed geocell in the field.
To simulate the 90° forces, an X-shaped sample from the geocell is wrapped round two rollers in a jig apparatus clamped to the tensile test machine. The test is conducted at rate of 100 mm/min, until a tensile split failure of the weld occurs.
X-shaped sample is wrapped in a jig apparatus clamped to the tensile test machine
The following are the minimum geocell seam weld strength values for categories B-D (±7%) according to ISO-13426-1,
Part 1, Method C:
- Seam Weld Strength – Weld Splitting (perforated): from 16 to 22 kN/m (minimum value)