Tech Briefs

Soil Mechanics with ADINA

ADINA is used widely in many fields of applications, including the field of geomechanics. Currently, ADINA offers the following geotechnical material models: Drucker-Prager, Mohr-Coulomb, Cam-clay, and a curve description model. These models can be combined with the following ADINA features:

  • two- and three-dimensional solid elements;

  • birth and death of elements (useful for tunnel-type studies);

  • initial stresses and strains;

  • gravity loading;

  • small and large deformations; and

  • associated or non-associated flow rules.

To illustrate the use of ADINA in the field of geomechanics, we present the solutions of two common soil mechanics problems using the Mohr-Coulomb material model. The first problem is the classical strip footing problem on a soil foundation, in which a uniformly distributed pressure is applied to model the effect of the footing (see Fig. 1 below).

Figure 1. Schematic of first problem

Due to vertical symmetry, only half of the domain is considered. The finite element mesh consists of 9-node two-dimensional solid elements deforming in plane strain. Fig. 2 below shows the load-displacement curves obtained for the associated and non-associated analyses, with two runs presented for each case. The movie above shows the evolution of the effective stress in the foundation for the non-associated analysis.

Figure 2. Results of first problem: load-displacement curves

The second problem considers a tunnel in which the initial support of the tunnel roof is gradually removed (see Fig. 3 below). The objective is to establish the displacement of the tunnel roof as the support is being removed. The support is modeled as a radial pressure.

Figure 3. Schematic of second problem

The results obtained show that plastification starts occurring between 50% and 55% of pressure removal and that the final plastic radius (i.e., when there is no pressure in the tunnel) is 8.85 m (see Fig. 4 below). Finally, Fig. 5 shows the evolution of the radial displacement of the tunnel as it is unloaded.

Figure 4. Results of second problem: band plot of Mohr-Coulomb flag
in Region A of Fig. 3

Figure 5. Results of second problem: evolution of tunnel's radial displacement

These examples illustrate only some of the powerful analysis capabilities of ADINA for solving geomechanics problems.