6. D modeling

We recall that modeling D concerns the use of model MCC [r7.01.48]. It is characterized by:

• A hydrostatic compression path in drained condition up to a pressure equal to \(2\) MPa.

• An undrained path by maintaining lateral stresses on the sample while imposing a vertical compression displacement.

6.1. Characteristics of modeling

Same as modeling A.

6.2. Tested sizes and results

At moment \(t=2\), at the end of an undrained load path, the components \(\sigma'_{xx}\) and \(\sigma'_{zz}\) of the effective stress tensor, and water pressure \(PRE1\), are tested at node NO8. The reference values are non-regression values.

Fig. 6.1 shows the path of the effective stresses in their meridian plane, where:

\[\]

sigma’_m=frac {mathrm {tr} (boldsymbol {sigma} “)} {3},quadsigma’_ {eq} =sqrt {frac {3} {tr} {tr} (boldsymbol {sigma} “-sigma’_mboldsymbol {I}) :(boldsymbol {sigma}) :(boldsymbol {sigma}) :(boldsymbol {sigma}) :(boldsymbol {sigma} “-sigma’_mboldsymbol {I})}

The load is hydrostatic up to stress \(-\sigma'_m=2\) MPa (drained isotropic compression phase). Then, during undrained loading, the diverter becomes non-zero and plastic flow occurs very early. The stress path joins the critical state line of equation \(\sigma'_{eq}+M(\sigma'_m-\sigma_0)=0\) [r7.01.48] _ during which the mean effective pressure \(-\sigma'_m\) decreases. This path is similar to that obtained with modeling A.

Fig. 6.1 Equivalent stress response and effective stress path in the meridian plane (D modeling).