In unsaturated soils, the foundation bearing capacity is highly influenced by soil suction. In dry weather, for instance, the lower soil water content results in a higher suction pressure and, therefore, in higher bearing capacity. On the other hand, in rainy periods the increase in soil water content causes simultaneously reduced suction and bearing capacity. As a result, load tests in unsaturated soils require concurrent measurements of the suction acting on the soil. In the most recent pile load tests, conducted in Experimental Foundation Field of the University of Sao Paulo, at Sao Carlos, Brazil, bore holes were made near the piles, and soil samples taken at every 1.0 m depht. Having obtained the correspondent volumetric water contents, and using characteristic curves previously obtained in the laboratory, the matric suction at each depth at which samples were taken, was determined. This rather simple technique made it possible to obtain the average soil suction during each load test.
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