Plate testing can be used to evaluate the support capacity of sub-grades, bases and in some cases. Data in the tests will be applicable for the design of both rigid and flexible pavements. In plate bearing test, a compressive pressure is applied through plates relatively big size and the deflections are measured for various pressure values. The deflection level is generally confined to some very low price, in the sequence of 1.25 to 5 mm and therefore the deformation caused may be partially elastic and partly plastic because of compaction of the stressed mass using negligible plastic deformation. The plate-bearing test was devised to evaluate the supporting power of sub par levels or any pavement layer by utilizing plates of larger diameter. The plate-bearing test was supposed to locate the modulus of sub grade reaction in the Westergaard's investigation for wheel loading pressures in cement concrete pavements. Test Procedure The test site is prepared and loose material is removed to ensure the 75 cm diameter plate rests in contact with the dirt sub-grade. The settlement dial gauge is set corresponding. A load is applied by way of jack, enough to induce an ordinary settlement of approximately 0.25 cm. Whenever there isn't any perceptible increase in compensation or any time the rate of compensation is less than 0.025 mm a minute (in the case of soils with high moisture content or in clayey soils) the loading dial reading along with the settlement dial readings are mentioned. Deflection of the plate has been measured by means of deflection dials; put usually at one third points of the plate near it's outer border. To minimize bending, a string of plates should be used. Average of three or four settlement dial readings is taken because the settlement of this plate corresponding to the load. Load is then increased until the typical settlement increase to a additional amount of approximately 0.25 mm, along with the burden and average settlement readings have been noted as before. The process is repeated till the settlement is all about 1.75 mm or more. Allowance for moisture and correction for little plate size should be dealt. The pressure corresponding to some settlement is obtained from the graph.
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