Numerical Study of the Dilatometer Insertion and Membrane Expansion in Sand

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4. Numerical Study of the Dilatometer Insertion and Membrane Expansion in Sand

The flat dilatometer DMT is an in-situ test where a wedged blade is inserted into the ground and then a circular membrane is expanded to measure inflation and deflation pressures. Since the inflation pressure is counteracted by the soil horizontal stress, soil geotechnical parameters can be correlated. However, the pressure readings are carried out on soil affected by the blade insertion. This fact has motivated this work, which focuses on the displacements and stresses variations caused by the blade insertion in sand. Numerical simulations were performed using 2D and 3D finite element models in Abaqus adopting an explicit scheme, which allows the modelling of the blade insertion in consecutive steps and, subsequently, the membrane expansion. 2D and 3D results in loose sand show that during blade insertion, high stresses are concentrated in front of the blade wedge, i.e., close to the blade tip. Moreover, in front of the membrane, stress levels were found to significantly reduce after the blade insertion. Furthermore, during membrane expansion, horizontal stresses in front of the membrane increased up to values in the range of those found during insertion in the blade wedge. It can be concluded that despite the alteration in the soil in front of the membrane due to the blade insertion, the soil recovers almost to the original stress state, allowing subsequent inflation pressures to represent the in situ soil state closely.

5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG2025)

3 - Constitutive models and soil behaviour modelling