Some laboratory experiments related to the results of pressuremeter tests.

The results of an undrained pressuremeter expansion may be interpreted to provide the stress-strain curve and the total stress path followed by the elements of soil around the instrument. If pore-pressures are measured during the expansion the effective stress path followed by the soil can also be deduced. Stress-strain curves and total and effective stress paths are presented for pressuremeter tests on three different clays at different overconsolidation ratios. It is possible to use a true triaxial apparatus to apply the same strain path to a single element of soil as is followed by the elements of soil around the pressuremeter. The results of three such true triaxial tests on samples of clay with different overconsolidation ratios are presented and discussed in some detail. This presentation is made first in terms of pressuremeter stress and strain parameters, but because more complete information about the state of stress in the element is obtained in the laboratory tests, a second presentation in terms of octahedral stress and strain components is also possible. Patterns of behaviour observed in the laboratory and in the ground are compared and the validity of some of the assumptions made in interpreting the pressuremeter test results is assessed in the light of these comparison