Dynamic Plate Test Devices (DPT)

Dynamic Plate Test Device is a term used to describe various types of equipment primarily used to assess the in situ performance and strength of pavements and foundations or granular materials using a test load dynamically applied through a circular plate. They include devices commonly termed Falling Weight Deflectometer.

Dynamic Plate Test devices can either be handheld machines or devices built into a vehicle or mounted on a trailer and towed behind a vehicle. Each device incorporates a circular loading plate that is placed onto the surface under test. The device applies a known load to the plate creating an impact load. The vertical deflections produced by the impact are measured at the centre of the plate and optionally at a series of radial positions from the centre. The measured deflections are a function of the applied load and are used to determine the structural condition of the structure under test.

DPTs are classified by the load that they can apply to the test plate. There are four main classifications, A to D:

• Class A - Lightweight Deflectometer (LWD) - 1- 15 Load Range (kN)
• Class B - Falling Weight Deflectometer (FWD) 30-120 Load Range (kN)
• Class C - Heavyweight Deflectometer (HWD) 30-240 Load Range (kN)
• Class D - Super-Heavyweight Deflectometer (SHWD) - 30 -300 Load Range (kN)

Class A devices are typically used for assessing the in situ structural condition of pavement foundations in the construction of new roads, airfields, ports and other structures. Class B, C and D devices are typically used for assessing the structural condition of in-service road pavements, airfields, ports and other structures.

The Accreditation and QA requirements for Class B, C or D Dynamic Plate Devices are given in the Accreditation and QA specification .

Accreditation and QA of DPT devices Issue 3.0 Sept 2020 

If you are looking for a contractor to undertake a survey using a Class B, C or D Dynamic Plate Device on your behalf, you may wish to check the list of DPT survey devices below. On this page you can also find the latest accreditation certificates. In this table machines are referred to as having met criteria if they have met the mandatory criteria as defined in the Accreditation and QA specification for these devices. Some Network Authorities may also require a specific level of performance in some or all of the additional tests. Please see the certificates for more detail on the performance of these devices in these additional tests. The Department for Transport provides guidance on the usage of DPTs in the assessment of new foundation construction and for in-service pavement assessment.