Multicycle expansion tests in natural soils Essais d'expansion multicycle dans les sols en place

This paper presents an application of multicyclic expansion tests carried out with a pressuremeter at two experimentation sites to evaluate soil susceptibility to this type of solicitation. These unique pressuremeter tests, interpreted in terms of deformation (volume change or radial strain) and number of cycles, offer relationships as a function of cyclic shear ratio. New test procedures and probe enhancements were also implemented to develop additional data and to improve the quality of these tests. These cyclic tests were performed using a pre-bored Menard pressuremeter as well as a new pressuremeter probe equipped with a miniature pore pressure transducer. Two sites were studied, one located in French Antilles and the second one located in Brittany (France), both consisting of normally consolidated sandy and silty soils profiles. An estimation of the relationship between cyclic stress ratio applied during the tests and the number of cycles to reach failure are presented and discussed in this paper. These results were compared to traditional cyclic laboratory test results and showed great potential for this in situ testing method. The results were used to develop preliminary charts for liquefaction prediction. This article presents a summary of the analysis and application of these cyclic pressuremeter tests.