Interpretation of load tests on bored piles in the city of Matera

This paper briefly reviews several calculation methods to evaluate the bearing capacity expressed in terms of undrained strength (cu) of piles bored in clay for their entire length and of piles whose tip is embedded into weak rock. The scope of the paper is to compare the results obtained with those from full-scale pile tests. These tests were carried out within the city of Matera which is well studied from a geotechnical point of view and for which there are statistically significant data on the geomechanical properties of the Subapennine Blue clays and the underlying Gravina Calcarenites. This represents the first attempt to show, on the basis of laboratory and field data, the influence of variability of the above mentioned soils and rocks on the real behaviour of deep foundations. For piles completely bored into Matera clay, the calculation in terms of total stress are able to interpret sufficiently well the bearing capacity of the piles. For piles having their toe embedded in calcarenite, the variability of the strength of the weak rock presents greater uncertainties in the calculation of base and soft resistance.