Piling mat testing

What does piling mat testing actually measure?

It measures how much the constructed working platform settles under a known applied pressure at each test position. The test is normally a plate bearing test: a plate is loaded in stages against a reaction and the settlement recorded at each increment, producing a load-settlement result for that position. The result describes how the platform behaved where it was tested. Whether that satisfies the platform design is a judgement for the temporary works designer.

Why won't my piling contractor bring the rig on without a platform test?

Because piling contractors normally require written confirmation that the platform has been designed, built to that design and will be maintained, before tracking a rig onto it. In practice that confirmation is the working platform certificate, signed by the principal contractor and handed to the piling contractor before piling starts. Measured test data is the evidence behind that signature, which is why certificates are often held up waiting for testing.

Which guidance is piling mat design and testing usually carried out to?

Granular working platforms are normally designed to the current Temporary Works Forum guidance on granular working platforms, which replaced the 2019 edition, and some specifications still name the earlier BRE report BR 470. The plate bearing test itself is commonly carried out in accordance with BS 1377-9. Your project specification takes precedence over any general guidance, so send it across and we will confirm the method, plate size and loading before we attend.

Can Hixtra sign the working platform certificate?

No, the working platform certificate is signed by the principal contractor and issued to the piling contractor before work starts, and we are not a party to it. Our role is to provide measured plate bearing data at the agreed positions, reported factually. The platform design, the decision that the platform is adequate for the plant proposed and the certificate itself remain with the designer and the principal contractor.

Should we test the formation before the mat is built, or the finished platform?

They answer different questions, and on some projects both are specified. Testing the formation before construction gives the designer the subgrade strength that the platform thickness is designed against, which matters where the ground is variable or the design is still being developed. Testing the finished platform verifies what was actually built and placed. The specification usually makes clear which stage is required, and the two visits are planned around the earthworks programme.

What plate size and test pressure should be used on a piling mat?

Both should be set by the platform designer rather than chosen on site. Guidance on granular platforms warns that a small plate stresses only a shallow zone and may have little influence on the subgrade beneath a rig track, so plate diameter should relate to the track or outrigger pad being represented. Plate diameters commonly run from 300mm to 600mm, with larger plates used where the loaded area justifies it. The maximum pressure is normally the design bearing pressure plus an agreed margin.

How many test positions does a piling mat need and where should they go?

The number and location are set by the platform designer or temporary works engineer, based on the platform area, how it was built and how variable the underlying ground is. Positions are usually spread across the platform rather than clustered, and typically include rig standing areas, any part built over softer ground or backfilled services and areas placed late or in poor weather. We test wherever you mark up and record each position in the report.

What condition does the platform need to be in before you arrive?

It should be fully constructed to the design thickness, compacted and reasonably level and clean at each test position. Standing water, loose surface material or a rutted finish affects how the plate seats and can distort the result. We also need safe access for a reaction machine, normally a tracked excavator, at every position, plus a working area that stays clear of plant movements while each test is running.

What happens if the results don't meet the design assumption?

We report the measured load and settlement data as recorded, and the designer decides what it means for the platform. In practice the usual outcomes are additional platform thickness, reworking or replacing the material in that area or a change to the plant allowed to track on it. We can return and retest once remedial works are complete, with the retest positions agreed with the designer beforehand rather than chosen on the day.

What will the piling mat test report contain?

Each test position is reported with its reference and location, the plate diameter used, the applied pressures, the settlement recorded at each load increment and the resulting load-settlement data. The report states the method followed, the date, the conditions on site at the time and the accreditation status of the result. It is issued to whoever instructs the work, and is commonly passed on to the temporary works designer and the piling contractor.

Is piling mat testing covered by your UKAS accreditation?

Hixtra holds UKAS accreditation to ISO/IEC 17025 for the tests listed in its schedule of accreditation, number 8996. Accreditation is specific to the listed methods and scope, so it attaches to particular methods rather than to a service as a whole, and each report states the status of the result. Ask us to confirm whether the test you need is covered before the work is booked.

What do you need to quote for piling mat testing?

Send the site postcode, the platform specification or design, the required bearing pressure, the number and location of test positions and your preferred dates. Cost is driven mainly by the number of positions, travel to site, whether you can provide the reaction machine and any standby, out-of-hours or weekend working. Call 01908 505833 or email enquiries@hixtra.co.uk and we will price the scope.