Abstract

The paper shows recent experience in performing and interpreting the three most common in situ tests for site characterization: cone penetration test (CPT), seismic dilatometer test (SDMT) and Menard pressuremeter Test (MPT). It is shown that an adequate selection of in situ test methods for site characterization can be used to correctly predict the pile head load-settlement curve. Menard pressuremeter design rules, which were established in the 1st and a draft version of the 2nd generation of Eurocodes, can be applied to SDMT readings to obtain the pile bearing capacity. It was found that corrected lift-off pressure p0 obtained in the SDMT test is similar to the Menard limit pressure pl in clay, while pressure p1 (SDMT) is similar to pl in sand. All results used in the analysis are obtained on a large-scale project where investigations are strictly controlled and performed in accordance with Eurocode standards.

Abstract

The Dilatometer Fondasol Test (DFT) is a unidirectional loading test in a borehole that provides an in-situ stress-strain curve. Two rigid shells are spread in the soil at a constant displacement rate by several small hydraulic jacks. First results using this probe in soils were obtained by Besson (2022) who also provided methods to compute from the stress-strain curve both a pseudo-elastic modulus and a limit stress. However, additional data were required to establish strong correlations between the dilatometer parameters and the pressuremeter parameters. This paper introduces new results obtained in various sites in France and synthetises all the results obtained so far. For each site, pressuremeter soundings and dilatometer soundings are carried out in pairs using the same drilling methods. DFT and PMT are performed at the same depths and at the same strain rate. For the computation of moduli and limit stresses, semi-automatic methods are employed to prevent subjective interpretations. Correlations are proposed between the dilatometer modulus and the pressuremeter modulus as well as between the dilatometer limit stress and the pressuremeter limit pressure. The established correlations, along with their limitations, are interpreted.