Plate testing is utilized to assess the support capacity of sub-grades, bases and in some cases sidewalk. Information from the tests are most applicable for the style of the rigid and flexible pavements. The deflection level is generally restricted to some low value, at the sequence of 1.25 to 5 mm so the deformation caused could be partially elastic and partially plastic due to compaction of this stressed mass with negligible plastic deformation. The plate-bearing test was devised to evaluate the supporting power of sub grades or any pavement layer by using plates of larger diameter. The plate-bearing test was initially intended to find the modulus of sub-par response in the Westergaard's analysis for wheel load stresses in cement concrete pavements.
The test site is prepared and loose material is removed so that the 75 cm diameter plate rests vertically in full contact with the soil sub-grade. The plate has been seated accurately and after that a chairs load equal to a pressure of 0.07 kg/cm2 (320 pound for 75 cm diameter plate) is applied and released after some seconds. The payoff dial gauge is put corresponding to zero loading.
A load is applied by means of jack, adequate to trigger an ordinary settlement of approximately 0.25 cm. When there isn't any audible increase in compensation or when the rate of settlement is less than 0.025 mm a minute (in the case of soils with high moisture content or in clayey soils) the load dial studying and the settlement dial readings have been noted.
Deflection of this plate is measured by way of deflection dials; put usually at one third points of the plate close to the outer border of it.
To minimize bending, then a collection of stacked plates should be used.
Typical of three or four compensation dial readings is accepted since the payoff of this plate corresponding to the load. Load is then increased till the typical settlement increase to some further amount of approximately 0.25 mm, along with the burden and normal settlement readings have been mentioned as before. The procedure is repeated until the settlement is about 1.75 mm or more.
Allowance for worst subgrade correction and moisture for small plate size ought to be dealt correctly.
The pressure corresponding to some payoff is obtained from the graph.