Fundamental Aspects of Pressuremeter Testing.

Of all in-situ soils tests, the pressuremeter test offers the greatest possibility for significantly improving our understanding of in-situ soil behavior and our ability to determine analysis and design parameters. Because the test directly provides the load-deformation response of the soil, with proper interpretation it is possible to obtain constitutive relationship of the in-situ soil. This study sought to increase our understanding of the influence of test procedures and certain soil conditions on the interpretation of the pressuremeter tests as it affects the determination of soil stress-strain and strength characteristics. Analytical studies included the influence on the derived pressuremeter and interpreted stress-strain curves of strain rate, pore pressure generation and dissipation, and borehole disturbance. These factors were found to affect, significantly, the stress-strain response and shear strength of the soil. Presence of a remolded annulus was found to be significant however initial unloading can even be more significant, especially for highly anisotropic and strain softening soils. Parametric studies indicate that pressuremeter expansion curves, and thus interpreted stress-strain response, obtained from commercially available probes with a standard strain rate 1min should not be significantly affected by partial drainage. The initial shear modulus was particularly sensitive to the above factors and it was tentatively concluded that the pressuremeter test is inappropriate for determination of this soil property.