S

Total settlement of centre of foundation = 25 mm

Note The Schmertmann approach is now preferred by most engineers to the De Beer and Martens' method.

The plate loading test

The results from a plate loading test can be used to predict the average settlement of a proposed foundation on granular soil. The test should be carried out at the proposed foundation level and the soil tested must be relatively homogeneous for some depth (not with conditions such as illustrated in Fig. 4.10).

If pi is the settlement of the test footing under a certain value of bearing pressure, then the average settlement of the foundation, p, under the same value of bearing pressure, can be obtained by the empirical relationship proposed by Terzaghi and Peck (1948):

Bj = width or diameter of test footing B — width or diameter of proposed foundation.

One aspect of using the results from a plate loading test for settlement predictions is that it is important to know the position of the ground water level.

It may be that the bulb of pressure from the test footing is partly or completely above the ground water level whereas, when the foundation is constructed, the ground water level will be significantly within the bulb of pressure. Such a situation could lead to actual settlement values as much as twice the values predicted by the formula.

where

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