Compaction tests · Plate load test · Ev2 · Modulus of subgrade reaction
Plate Load Test
We load a steel plate in steps with a hydraulic jack on the ground at foundation level or on compacted fill, and measure the settlement at each step with precision dial gauges. We report the bearing capacity, the modulus of subgrade reaction and, on fill, the Ev1, Ev2 and Ev2/Ev1 values.
Call us directly: +90 533 616 18 67
- 30–75 cm plates
- Ev1, Ev2 and k value
- Wind turbine foundations
- Since 2001 soil testing
- Reaction: truck or excavator
- Hydraulic jack and pressure gauge
- Loading plate, Ø 30–75 cm
- Dial gauges
- Reference beam
- Pressure bulb under the plate
Definition
What is the plate load test?
The plate load test (plate bearing test) is a field test in which a circular steel plate 30–75 cm in diameter placed at foundation level is loaded in steps and the settlement is measured at each step. The resulting load–settlement curve gives the bearing capacity of the ground and its settlement behaviour under load.
The same test also gives the modulus of subgrade reaction (k). On fill and road layers two loading cycles are carried out to find the deformation moduli Ev1 and Ev2 and the Ev2/Ev1 ratio, which indicates compaction.
The test can be carried out on the surface, in a pit or at the bottom of a borehole. It is simple and fast, and shows directly how the ground behaves under real load. It is better suited than the CBR test to coarse aggregate fill. It is also used to check working platforms for piling rigs and crane outrigger pads.
At a glance
| Standards | TS 5744, BS 1377-9. DIN 18134 for Ev1/Ev2 on fill. |
|---|---|
| Plate | Circular steel, Ø 30–75 cm. |
| Loading | Hydraulic jack and pressure gauge, in steps. |
| Measurement | 2–3 dial gauges placed symmetrically around the plate. |
| Reaction | Excavator, loader or loaded truck. |
| Result | Load–settlement curve, bearing capacity, k, Ev1, Ev2 and Ev2/Ev1. |
What is it for?
Bearing capacity or fill control?
Bearing capacity of the formation
Natural ground at foundation level is loaded in steps up to its bearing capacity or to 2–3 times the safe bearing capacity. At each step the settlement is allowed to stabilise.
- Bearing capacity and settlement of shallow foundations
- Modulus of subgrade reaction (k) for raft foundations
- Wind turbine, tank and machine foundations
Fill and road layer control
The compacted layer is loaded in two cycles: first loading, unloading and second loading. The Ev1 and Ev2 moduli are calculated from the curves.
- Fill under foundations and ground improvement layers
- Under roads, railways, yard slabs and industrial floors
- Ev2 and Ev2/Ev1 checks against the specification
On site
How is the plate load test carried out?
- The surface is preparedThe test point is levelled at foundation level. A thin layer of sand is spread and levelled so that the plate sits fully on the ground.
- The plate is placedThe plate is placed horizontally in full contact with the ground.
- The jack and reaction are set upA truck or excavator is positioned over the plate. The hydraulic jack is placed between the plate and the reaction, at the centre of the plate.
- The dial gauges are fitted2–3 dial gauges are placed symmetrically around the plate. The reference beam holding them is supported outside the zone of influence of the load.
- Loading in stepsThe load is increased in steps. At each step readings are taken at 1, 4, 10, 20, 40 and 60 minutes and then hourly until the settlement stabilises. In the Ev test, unloading and a second loading follow.
- Assessment and reportThe average of the dial gauges is taken as the plate settlement. Load–settlement and settlement–time curves are drawn and bearing capacity, k and Ev values are calculated.
Reading the results
How are Ev1 and Ev2 calculated?
In the Ev test the plate is first loaded to the maximum stress, then unloaded and loaded a second time. A deformation modulus is calculated from each loading curve:
Ev = 1.5 · r · Δσ / Δs
Here r is the plate radius and Δσ and Δs are the differences in stress and settlement, taken between 30% and 70% of the maximum stress.
- Ev2 shows the bearing capacity of the layer. The higher the value, the stiffer the layer.
- Ev2/Ev1 indicates compaction. The smaller the ratio, the better the layer is compacted. Specifications usually give an upper limit.
Assessment and planning
Ev2, Ev2/Ev1 and reaction load calculator
The starting values are an example. The calculator finds Ev1, Ev2 and Ev2/Ev1 from the two loading cycles and compares them with the specification values you enter.
It also calculates the reaction load needed for the chosen plate diameter and maximum stress. This is used to plan which truck or excavator to bring to the test.
Enter the target Ev2 and Ev2/Ev1 values from the project specification. This tool is for preliminary assessment.
Price
Plate load test price
The price depends mainly on the number of tests, the purpose of the test, the plate diameter and the project location. It is given per project or as a unit price per test.
- The more tests on the same site, the lower the price per test
- Bearing capacity tests take longer because settlement must stabilise at each step
- Larger plates and higher stresses need a heavier reaction load
- The reaction vehicle is provided by the site unless agreed otherwise
Fill in the details and your message opens ready to send on WhatsApp. Add a plan showing the test points to the same chat if you have one.
Before the test
What must be ready on site?
- The test point must be at foundation or layer level, flat and clean
- A loaded truck, excavator or loader must be ready as reaction
- There must be access and space for the vehicle to reach the plate
- No vibrating plant should work near the point during the test
- For fill control, compaction of the layer must be complete
After the test
What is in the report?
- Test points, plate diameter and test set-up
- Load, time and settlement readings for each step
- Load–settlement and settlement–time curves
- Assessment of bearing capacity and modulus of subgrade reaction (k)
- For fill control, Ev1, Ev2, Ev2/Ev1 and compliance with the specification
References and site work
From our plate load tests
Comparison
Plate load test, LWD or nuclear gauge?
| Test | What does it give? | When to choose it? |
|---|---|---|
| Plate load test | Bearing capacity, k, Ev1, Ev2 | Formation, Ev2 checks required by the specification, reference test |
| Light weight deflectometer (LWD) | Dynamic deformation modulus Evd | Fast fill checks at many points without a reaction load |
| Nuclear density | In-situ density and moisture content | Fast check of degree of compaction against Proctor |
| Sand cone | In-situ dry unit weight | Classic compaction control, calibration of the nuclear gauge |
| Plate load test on piles | Load–settlement at the pile or column head | Loading on jet grout columns, stone columns and pile heads |
| Pile load test | Behaviour of the pile under real load | Capacity verification for piled foundations |
Frequently asked questions
About the plate load test
What is the plate load test?
A field test in which a circular steel plate 30–75 cm in diameter placed at foundation level is loaded in steps with a hydraulic jack and the settlement is measured at each step. The load–settlement curve gives the bearing capacity, the modulus of subgrade reaction and the deformation moduli of the ground.
Which standard is the plate load test carried out to?
For bearing capacity, TS 5744 (BS 1377-9 also describes the test). Where Ev1 and Ev2 values are required on fill and road layers, DIN 18134 is used. The project specification decides which standard applies.
What are Ev1 and Ev2?
Ev1 is the deformation modulus calculated from the first loading curve and Ev2 from the second loading curve after unloading. They are found with Ev = 1.5 · r · Δσ / Δs from the slope between 30% and 70% of the maximum stress.
What does the Ev2/Ev1 ratio show?
How well the layer is compacted. In a well-compacted layer the settlement on second loading is close to that on first loading, so the ratio is small. Specifications usually give a lower limit for Ev2 and an upper limit for Ev2/Ev1.
How is the modulus of subgrade reaction (k) found from a plate load test?
The modulus of subgrade reaction is the ratio of the stress under the plate to the corresponding settlement and is calculated from the load–settlement curve. It is used in the design of raft foundations and slabs on grade. Because plate size affects the result, it is corrected for the foundation size.
How long does a plate load test take?
The Ev test for fill control usually takes 15–30 minutes. In a bearing capacity test on the formation, the settlement must stabilise at each step, so the duration is longer depending on the soil.
What is used as reaction load?
Usually a loaded truck, excavator or loader. The weight needed depends on the plate diameter and the stress to be applied. Unless agreed otherwise, the reaction vehicle is provided by the site.
What are the limits of the plate load test?
Because the plate is much smaller than the actual foundation, it only affects the ground to a depth of about 1.5–2 times the plate diameter. In layered ground, weak layers at depth may not show in the test, so results are assessed together with the site investigation.
What is the difference between the plate load test and the light weight deflectometer (LWD)?
The plate load test applies a static load with a hydraulic jack and needs a reaction load. The LWD applies a dynamic load with a falling weight, needs no reaction load and is much faster. If the specification requires Ev2 the plate load test is used; for fast checks at many points the LWD is preferred.
What determines the price of a plate load test?
Mainly the number of tests, the purpose of the test, the plate diameter and the project location. Bearing capacity tests take longer than Ev tests because settlement must stabilise. The price is given per project or as a unit price per test.
Will your ground carry the load? Measure it and know
Send us the number of tests, the purpose, the plate diameter and the project location. We will prepare the test programme and send our quote.
Sarıgöl Mah. Mezarlık Sk. C1 No: 108 İç Kapı No: 63
Gaziosmanpaşa, Istanbul, Turkey
Mobile / WhatsApp: +90 533 616 18 67
Phone: +90 212 369 00 16
info@zeminarastirma.com
Mon–Fri 08:00–19:00 · Sat–Sun 08:00–14:00 (GMT+3)