A plate load test measures how the ground responds to load, directly at foundation level. It is used to estimate bearing capacity and settlement, and it is covered by IS 1888.
Plate load test procedure
- Excavate a test pit to the proposed foundation level. The pit is kept wider than the plate, usually at least five times its width.
- Place a steel plate, usually 300 mm to 600 mm in size, on a level surface.
- Set up the loading arrangement, with a hydraulic jack against kentledge or a reaction frame.
- Fix dial gauges to measure settlement.
- Apply a small seating load, then release it.
- Apply the load in increments, recording settlement over time until it nearly stops at each stage.
- Continue until failure or until a set settlement is reached.
Reading the result
The readings are plotted as a load-settlement curve. In dense sand or stiff soil, the curve often shows a clear break that indicates failure. In softer soil, the failure point is less clear and engineers use a settlement-based criterion.
Important limitations
- Scale effect: a small plate only stresses shallow ground. A real footing influences much deeper soil, so a weak layer below may be missed.
- Short duration: long-term settlement in clay is not captured, so consolidation tests are still needed.
- Water table: the result can be affected if groundwater later rises.
Use it with borehole data, not instead of it. A full investigation shows what lies below the zone the plate tests.
FAQ
What is the plate load test used for?
Mainly to estimate safe bearing capacity and settlement of shallow foundations, and to check compacted ground.
Can the plate load test be used for clay?
It can, but it does not capture long-term consolidation settlement, so it should be read with laboratory results.
Which code covers the test?
IS 1888 is the Indian Standard for load tests on soils.
Talk to our team
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