(2003), “Standard Test Method for Bearing Capacity of Soil for Static Load and Spread Footings.”
The test procedures are as follows:
1.Bearing plate. The ASTM test procedures state: “Three circular steel bearing plates, not less than
1 in. (25 mm) in thickness and varying in diameter from 12 to 30 in. (305 to 762 mm), including
the minimum and maximum diameter specified or square steel bearing plates of equivalent area.”
As an alternative, small concrete footings can be cast and tested in place of the steel plate.
2.Test location. Ideally, the plate load test should be at the same location and elevation as the bot-tom of the proposed footing. The plate load test could be performed at the bottom of test pits or
trenches and, in general, it is desirable to perform at least three plate load tests. Also the site con-ditions should be similar to the in-service conditions. Thus if it is expected that the soil will
become wetted in the future, then the soil in the area to be tested should be prewetted.
3.Loading of plate. Loads are applied in increments such that each load is not more than one-tenth
of the bearing capacity of the soil in the area being tested. The load must be accurately measured
and applied in such a manner that the load reaches the soil as a static load, without impact, fluc-tuation, or eccentricity. After the application of each load increment, it should be maintained for
a time interval of not less than 15 min. The load is increased until there is a definite failure of the
soil or until the settlement of the plate reaches 10 percent of the plate width. The load is then
removed in increments and the rebound deflections are also recorded.
4.Pressure versus settlement curve. The bearing pressure is calculated as the load divided by the
area of the plate. The pressure versus settlement from the plate load test can then be plotted.
The plate load test can also be used to directly estimate the settlement of a footing. For settlement
of medium to dense sands caused by an applied surface loading, an empirical equation that relates
the depth of penetration of the steel plate S
1
to the settlement of the actual footing Sis as follows
(Terzaghi and Peck, 1967):