# Plate Load Test

The plate load test (see Figure 1 and 2) can be used to measure the modulus of subgrade reaction for in situ material. The test involves pressing a steel bearing plate into the surface to be measured with a hydraulic jack.

- Canonical URL: https://pavementinteractive.org/reference-desk/design/design-parameters/plate-load-test/
- Last updated: 2018-09-19
- Review: reviewed by licensed professional engineers on the previous Pavement Interactive site, where reviewers were not recorded by name
- Standards: AASHTO T 222, ASTM D1196

The plate load test (see Figure 1 and 2) can be used to measure the [modulus of subgrade reaction](https://pavementinteractive.org/reference-desk/design/design-parameters/modulus-of-subgrade-reaction/) for in situ material. The test involves pressing a steel bearing plate into the surface to be measured with a hydraulic jack. The resulting surface deflection is read from dial micrometers near the plate edge and the modulus of subgrade reaction is determined by the following equation:

![Plate load test schematic](https://pavementinteractive.org/wp-content/uploads/2007/08/PLATE.jpg)

*Figure 1.* Plate load test schematic

![Plate load test](https://pavementinteractive.org/wp-content/uploads/2007/08/Plate_bearing.jpg)

*Figure 2.* Plate load test

$$k = \frac{P}{\Delta}$$

where:

- $$k$$ = spring constant = modulus of subgrade reaction
- $$P$$ = applied pressure (load divided by the area of the 762 mm (30 inch) diameter plate)
- $$\Delta$$ = measured deflection of the 762 mm (30 inch) diameter plate

The 1993 AASHTO *Guide* offers the following relationship between k-values from a plate bearing test and [resilient modulus](https://pavementinteractive.org/glossary/resilient-modulus/) ($$M_{R}$$):

$$k = \frac{M_R}{19.4}$$

## Standard Test Methods

- AASHTO T 222 and ASTM D 1196: Nonrepetitive Static Plate Load for Soils and [Flexible Pavement](https://pavementinteractive.org/glossary/flexible-pavement/) Components, for Use in Evaluation and Design of Airport and Highway Pavements