Plate Load Testing

A plate load test measures the relationship between applied pressure and surface settlement beneath a rigid plate. Results can support assessment of near-surface ground response, earthworks verification or pavement-related parameters when the procedure and interpretation match the project purpose.

The pressure, settlement-increment and subgrade-modulus equations are on the separate Plate Load Test Pressure and Modulus Calculation page.

Define the purpose before testing

The required plate size, reaction system, load sequence, hold periods, measurement accuracy and interpretation depend on whether the test is intended to assess load-settlement response, modulus of subgrade reaction, working-platform behaviour or another project requirement.

A result should not be interpreted outside the scope of the selected test method.

Test arrangement

The test record should document:

• Plate dimensions, rigidity and contact preparation
• Test level, ground condition and material description
• Reaction system and load measurement device
• Independent settlement reference and gauge arrangement
• Seating load, load increments, hold periods and unloading sequence
• Weather, groundwater and disturbance during testing
• Calibration and equipment identification

Raw time, load and settlement observations should be retained, including repeated or corrected readings.

Load-settlement curve

Interpretation should use the complete load-settlement curve, not only a single calculated number. Seating, nonlinearity, creep, unloading and rebound can affect the selected result. The exact points used for a secant or tangent parameter should be recorded.

Modulus of subgrade reaction

The modulus of subgrade reaction is a pressure-to-settlement ratio over a defined range. It depends on plate size, material, stress level and test procedure. It is not a fundamental soil constant and should not be transferred directly between applications without an approved conversion or design method.

Scale and depth of influence

A test plate influences a smaller and shallower ground volume than many full-size foundations. Layering, weak material below the influence zone, drainage and footing geometry can cause field behaviour to differ materially from the plate result.

Calculation resources

• Plate Load Test Pressure and Modulus Calculation
• Bearing Capacity of Soil and Foundations
• Soil Compressibility and Foundation Settlement

Engineering note

Plate load results should be interpreted using the specified test method and project design basis. They do not provide a universal allowable bearing pressure or full-size foundation settlement prediction.