An analysis of pressumeter Holding Tests

The self-boring pressuremeter - Camkometer - was used to define the permeability characteristics of Fucino clay using strain-holding and stress-holding tests. The probe was expanded to a specific value of cavity strain; then the strain or stress was held constant while the dissipation of the excess pore pressure, induced by the initial expansion of the probe, was monitored. The decrease of pore pressure obtained with time was used to derive the coefficient of consolidation for horizontal flow ch. To account for the two-dimensional nature of the problem and the non-linear soil behaviour, numerical analyses were performed which simulated the tests by using the finite element program CRISP, which employs a coupled consolidation theory and the modified Cam clay soil model. The numerical simulation was used to investigate the dependence of the maximum excess pore pressure on the stress history and on the strain level, the necessity to account properly for the soil non-linearity in order to follow the decrease of cavity pressure with time (in a strain-holding test) and the influence of the cavity pressure on the dissipation curves. It was also possible to establish whether conditions during a cavity expansion were undrained, or whether the loading was monotonic, as well as the relevance of ch on both phenomena