Please note
The test rates listed in this website are only applicable to clients who comply with the requirements in our Testing Notes and Terms and Conditions and pay all submitted invoices within 30 days from the date of invoice
Triaxial Permeability
Triaxial Permeability
| Description | Price |
| Triaxial Permeability up to 4 days duration (BS EN ISO 17892-11 : 2019 ) |
£ 120.00 |
| Extra over days in excess of initial 4 days | £ 38.50 per day |
| Remoulding specimen | Dependent upon specimen size |
Results given
Coefficient of Permeability
You provide
- Remoulding conditions, if applicable.
- Effective consolidation pressure.
- Differential pressure or hydraulic gradient (optional).
Typical use(s)
Ensuring permeability of landfill clay liner meets required specification.
Material required
- If remoulded, 2 kg (for 100mm diameter specimen).
- If undisturbed,100mm diameter core-cutter or liner sample, at least 100mm intact length.
Considerations
-
- The duration of this test is material dependent.
- To ensure accurate, repeatable results, we follow the British Standard method (BS1377 : Part 6 : Clause 6:1990) involving saturation to a B value of 0.95, followed by consolidation to at least 95% pore pressure dissipation.
- Although not a rapid test, typical durations are often less than some people’s preconceptions.
- As a rough guide, we have found the following chargeable durations typical:
| Material Type | Typical Chargeable Duration |
| Cement bentonite grout mixes | 7 days |
| Stiff London Clay | 9 days |
| Very soft alluvial very silty clay (material
already saturated, but long consolidation stage) |
8 days |
| Silty sandy boulder clay | 6 days |
| Bentonite enriched sands | 10 days + (see note below) |
Note: BES typically displays a gradually lessening permeability with time as the bentonite hydrates and swells. As a definitive linear permeability is unclear, we liaise with the client to ensure we meet their testing requirements. Where testing durations are anticipated to be exceptional, we may negotiate special rates for any additional days.
Constant Head Permeability
Constant Head Permeability in a Permeameter
| Description | Price |
| Constant Head Permeability using a permeameter Up to 4 days duration includes remoulding (BS EN ISO 17892-11 : 2019 : 6.2.2) |
£ 145.00 |
| Extra over days in excess of initial 4 days | £ 38.50 per day |
Results given
Coefficient of Permeability
You provide
Remoulding conditions
Note: High degrees of compaction may not be possible since the material is remoulded into acrylic, not steel, cylindrical apparatus.
Typical use(s)
Determining permeability for soakaways etc.
Material required
- 2 kg for material up to 6.3 mm particle size
- 6 kg for material up to 10 mm particle size
Note: For material over 10mm particle size we would only be able to test by this method the material passing 10mm for a British Standard test, or include test material larger than this for a non-standard test. Depending on the mix of particle sizes, the non-standard test may give a more accurate reflection of the permeability of the whole material, but the larger than permitted particles may also give a large variability in measured permeability. It cannot be known if removing oversize material will increase or decrease the measured permeability. Removing occasional gravel from a sand would be likely to increase the permeability as large impermeable regions were removed. Removing medium and coarse gravel which had been the main constituents to leave only sand and fine gravel could well decrease the permeability by reducing the size of the interstices between the particles and so restrict the flow between them. A more suitable test for non-cohesive materials up to 37.5 mm particle size is the Horizontal Permeability test, but this typically requires 200 kg of material (enough to fill a box 1000mm long by 300mm square cross section).
Considerations
This test is suitable only for samples with relatively high permeabilities (coefficients in the range 10-2m/s to 10-5m/s: typically no finer than fine sand / coarse silt). Please see the note in the ‘material required’ section regarding oversize material. For lower permeabilities, usually when checking that the material is impermeable enough to meet a specification, the Triaxial Permeability is a more appropriate test.
K H Head Method
K H Head Method
| Description | Price |
| Permeability in a triaxial cell with one back pressure system (up to 4 days duration) (K H Head “Manual of Soil Laboratory Testing” Volume 3 Chapter 20.4.2) |
£ 120.00 |
| Extra over days in excess of initial 4 days | £ 38.50 per day |
| Remoulding specimen | £ 20.00 |
Results given
Coefficient of Permeability
You provide
- Remoulding conditions
- Cell pressure
- Differential pressure or hydraulic gradient (optional)
Typical use(s)
Ensuring permeability of landfill clay liner meets required specification.
Material required
- If remoulded, 2 kg for 100mm diameter specimen.
- If undisturbed,100mm diameter core-cutter or liner sample, at least 100mm intact length.
Notes
This test is not in BS1377, so the same notes as found in the Accelerated Permeability section apply.
"Accelerated" Permeability
“Accelerated” Permeability
| Description | Price |
| Accelerated Permeability Client’s specification or Technical Procedure 60 |
Dependent on client’s specification |
| Extra over days in excess of initial 4 days | £ 42.00 per day |
| Remoulding specimen at as-received moisture content | £ 20.00 |
Results given
Coefficient of Permeability
You provide
- Test specification.
- Remoulding conditions.
Typical use(s)
Indication of coefficient of permeability before a definitive British Standard Triaxial Permeability (BS1377:Part 6:Clause 6: 1990) is available.
Material required
- If remoulded, 2 kg (for 100 mm diameter specimen).
- If undisturbed,100 mm diameter core-cutter or liner sample, at least 100mm intact length.
Notes
By its nature, this test is non-standard and the client will need to ascertain for themselves the suitability for their purposes of the specification provided, and the acceptability of that specification by their client.
It is our experience that in the majority of cases, the British Standard Triaxial Permeability test does not take significantly longer than an accelerated method (see considerations on the triaxial permeability section), and it has the benefit of being a nationally accepted method.
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