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Portugal 106

4 - Interpretation and eyaluatłon of test results - Systematic observations of struć -tures founded on sands has shown that Dutch penetrometer results give most valuable data for assessing the deformabilities of these formations. Samples tested in the łaboratory, prepared in such a way as to display the same deformability (for the same state of stress) as 'in situ¹, show also the suitability of the Dutch penetrometer test for measuring the internal friction in sands. (Fig. 1 and 2).

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(dcgrca)

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V \ i \ \

28 -1--—--——---

K>    20    30    40    70 ICO    200    300

Rp (kg/cm¹)

E (kg/cm²)    Rp (kg/cm²)

0“ (kg/cm²)

Fig. 1 - Young modułus versus point resis tance and overburden stress

Fig. 2 - Angle of internal friction versus point resistance for overburden stresses 0.5-1.5 kg/cm²

In clays or sandy-clays of medium consis -tency, either SPT tests or Dutch penetro -meter tests give overall information very useful for evaluating the shear strength of the formations. Deformability characteristics have also been evaluated from results of these tests. In this case, however, deviations are considerable as compared to results obtained in carefully selected samples or 'in situ' loading tests.

As regards clayeysoils, if they display poor consistency, neither SPT tests nor Dutch pe netrometer tests are suitable to characteri-ze them from the mechanical point of view. This may be concluded from comparison of these tests and in situ vane tests and also from studies on undisturbed samples.

For piles of usual dimensions, namelly up to 50-70 cm in diameter and 10-20 m in length, the method preconized by the Delft Laboratorium voor Grondmechanica to eva-luate the bearing capacity taking as a basis the Dutch penetrometer tests, has been tried and gave good results when compared with actual load tests.