Plate Load Tests

It is one of the earliest tests to be performed to determine the bearing capacity of soil. The test consists of making a pit, commonly at foundation level and measuring the settlements of a circular or square mild steel plate not less than 25 mm in thickness and 300 to 750 mm within size subject to gradual load increments. From the test output, load vs settlement curve is plotted and the ultimate bearing capacity of the soil is arrived at. This test has the subsequent limitations:

(a)  The results are indicative of the character of soil inside a depth of less than twice the width of the bearing plate that is commonly 300 to 750 mm. Because the actual dimensions of foundations are larger so that the settlements and shear resistance will depend on a much thicker stratum of the sub-soil.

(b)  It is a short duration test and does not provide an idea about consolidation settlement particularly in cohesive soils. Therefore, the results of the test could be misleading if the character of soil modifications at shallow depths, that is not uncommon.

(c)  Although for clayey soils, the bearing capacity (from shear consideration) for a larger foundation is almost the similar as for the smaller test plate; although in the case of dense sandy soils, the bearing capacity increases along with the size of foundation and thus, in such cases; the plate load test gives a conservative value.