Discussion on Session 4(b): pressuremeter, permeability and plate tests

Discussion reviewer John J. M. Powell

Building Research Establishment

The format of the discussion session was to take presentations prompted by the questions raised in the moderator's presentation and to include discussion from the floor.

R Whittle responded to the moderator's request to discuss some of the problems resulting from membrane compression in pressuremeter tests.

Figure 1 shows what happens when a cone pressuremeter (CPM) is inflated inside a thick wall metal cylinder. After contact with the cylinder wall the expansion should virtually stop. In practice, there is a significant non-linear response which is not very stiff. In this plot the steepest part is quoted as a slope in units of mm/GPa. Converting this to stiffness gives a modulus of only 500 MPa.