Load tests on five large spread footings on sand and evaluation of prediction methods

Abstract

The design techniques for many of today's modem shallow foundations are often based on figures and formulas developed as many as fifty years ago. These design techniques were developed in the early stages of foundation engineering and are generally conservative and exhibit significant scatter; being based more on intuition and experience than on scientific research. This is not to say that these methods lack merit as they have been utilized in the design of many great engineering projects. For years, the idea of performing full scale load tests on shallow foundations for pure research has not been popular and deep pile foundations have been used more readily in engineering. Today, this lack of full scale load test data is partly responsible for the engineering profession's lack of trust in the use of spread footings. For this study, five spread footings with sizes ranging from I to 3 m square were load tested to 150 mm of penetration. The footings were all constructed and tested in a similar manner at the same general location where the soil consisted of fairly uniform silty fine sand underlain by stiff clay at a depth of 11 m. To the author's knowledge, the testing program described in this work is of a magnitude never before seen for spread footings. A complete summary of the project and its results can be found in Section 6.