Plate Load Test – How it Works – Measuring Ev2 and Ev1
The Plate Load Test AX01 is the simple solution to determine the strain moduli Ev2 and Ev1 (a figure for the bearing capacity) and the ratio Ev2/Ev1 (a figure for the compaction level). The modulus is an indicator for the bearing capacity of the soil or flexible pavement under the loading plate.
For the test, the soil is loaded and unloaded in fixed steps using a circular loading plate and a hydraulic loading device.
The load plate is loaded by a hydraulic jack and it’s settlement is measured at increasing load increments. During two loading cycles, different loads will be applied in steps to the loading plate using a hydraulic hand pump. For each loading step, the corresponding settlement (deflection) of the plate is recorded. The device is equipped with an electrical force sensor to record the load and an inductive displacement gauge to determine the deflection.
A graph is then plotted of settlement against bearing pressure and will show settlement at any given load. This information is used to calculate the Modulus of Subgrade Reaction, a measure of the stiffness of the subgrade known as the K value. It is expressed as load per unit area per unit of settlement e.g. KN/m2/mm or KPa/mm.
The results of the test are evaluated immediately, shown at the display, and printed with the built-in thermo printer at the road-works. The test results can also be stored on a memory chipcard. Using a chipcard reader, the results can be transferred into an MS Excel sheet on a Windows-PC for further analysis.
In order to perform this test, it is important to have sufficient kentledge to jack against. The counter weight could be equipment you have on site such as an excavator, roller or a truck loaded with material. The choice of plate size depends upon the required bearing pressure, depth of influence required and the available kentledge.
The AX01 Plate Load Test comes with a 300mm load plate as standard but 600mm and 762mm load plates are available. The equipment comes with a 20T hydraulic jack but a 10T jack option is also available. The maximum bearing capacities are as follows: