Laboratory investigation of the loading rate effects in sand

Laboratory investigation of the loading rate effects in sand

Huy, N.Q.
Van Tol, A.F.
Hölscher, P.

2006-08-24

In order to improve the interpretation of the quasi-static (e.g. Statnamic) pile load tests, a research project has been started to investigate effects of the loading rate on the bearing capacity of a pile in sand. A series of laboratory tests has been carried out. The testing program consists of a series of triaxial tests for sand and a series of load tests on a model pile embedded in sand in a large calibration chamber. The research pointed at answering two fundamental questions: - The effect of loading rate on the strength of sand and on the bearing resistance of a pile in sand; - The characteristics of excess pore pressure in sand and in the sand near the pile toe during a quasi-static load test. The results of the triaxial tests are: - In dry sand, a higher loading rate gives higher shear strength. In the range of applied loading rates, the angle of internal friction of the sand increases up to 2 degrees (strength increases 5-10%). - During high speed tests on dry sand an excess of pore air pressure is observed. So the dry sand is not in fully air drained condition during these tests. - The effects of loading rate in dry sand increase with the increase of relative density. - In saturated sand, the shear strength increases about 5% due to the rate effect. But, the true rate effect may be obscured by cavitation which occurs during the test. - Before cavitation occurs, the excess pore water pressure is independent of the loading rate. It depends on the relative density of the sand.

Laboratory investigation
loading rate
sand
quasi-static
Statnamic
pile load
triaxial
load test
CT01.30
Funderingen en Bouwputten
CT01.33.11
Snelle methoden voor het testen van palen
Delft Cluster

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report

(c) 2006 Huy, N.Q.; Van Tol, A.F.; Hölscher, P.