Image made using the COMSOL Multiphysics® software and is provided courtesy of COMSOL.
The horizontal stresses, deformation and plastic regions are plotted from a model of the excavation of soil. The Drucker-Prager plastic model is used in the simulation.
As an add-on to the Structural Mechanics Module, the Geomechanics Module allows you to analyze geotechnical applications, such as tunnels, excavations, slope stability, and retaining structures. Utilizing a number of nonlinear geomechanics material models, it contains tailor-made physics Interfaces for investigating deformation, plasticity, creep, and failure of soils and rocks, and their interactions with piles, supports, and other manufactured structures.
The Geomechanics Module comes with standard nonlinear material models that describe metal plasticity through the von Mises and Tresca criteria. Yet, the essence of the Geomechanics Module is the nonlinear material models for soils, concrete, and rock that are built into physics interfaces modeling solid mechanics.
This model provides an estimation of the behavior of the soil during a tunnel excavation. The surface settlement and the width of the plastic region around the tunnel are important parameters needed to predict the reinforcements to use during the excavation.
Two study steps are used. The first computes the stress state of the soil before excavating the tunnel. The second computes the elastoplastic behavior after removing the soil inside the tunnel, and uses the in situ stresses calculated from the first step. In the first step, the soil is considered elastic and in the second step, a soil plasticity feature with Drucker-Prager criterion is added. The model is solved in 2D plane strain.
A common verification model for geotechnical problems is of a shallow stratum layer of clay.
In this model, a vertical load is applied to the clay strata top surface and the static response and collapse load are studied.
The clay is modeled as an elastic-perfectly plastic material and the Mohr-Coulomb yield condition under plane strain conditions is used. The response is studied using an associated as well as a non-associated flow rule.
Reinforced concrete beams are commonly used in modern construction due to their strength and durability. By simulating such beams, engineers can ensure that the resulting structures both perform well and are safe. With simulation apps, engineers of all levels of expertise can analyze and test different designs with ease.
The Parameterized Concrete Beam demo app focuses on the structural properties of arbitrary beam and rebar designs. App users have the option to modify a range of parameters such as geometric parameters of the beam, steel and concrete material properties, the distribution of the reinforcement bars, and boundary conditions at the beam’s end.
Results show axial stress in concrete and beams, deflection, and regions where plasticity occurs.
This deep excavation model is inspired by a benchmark exercise specified by a working group of the German Society for Geotechnics. In this model, a 20 m excavation is modeled with ten steps by means of a parametric sweep. The interaction between the soil and the retaining wall is modeled with contact pairs, and struts are activated as the excavation reaches their depths.
Concrete structures almost always contain reinforcements in the shape of steel bars (“rebars”). In COMSOL, individual rebars can be modeled by adding a Truss interface to the Solid interface used for the concrete. The solid mesh for the concrete and the rebar mesh can be independent, since the displacements are mapped from within the solids onto the rebar at a certain position.
This model shows how to set up a uniaxial compression test on a prestressed soil sample. Due to uniaxial compression and simple initial stress values, it is possible to determine the vertical yield stress analytically. The soil sample is modeled with soil plasticity and the Mohr-Coulomb criterion.
Isotropic compression is a common exercise in soil testing. The modified Cam-Clay model describes the relation between the void ratio and the logarithm of the pressure. In this example, a soil sample is placed inside cylinder 10 cm in diameter and 10 cm in height. Due to the symmetry, the model is solved in 2D axial symmetry. A boundary load produces isotropic compression conditions.
The triaxial test is one of the most common tests used in laboratory soil testing. The soil sample is normally placed inside a rubber membrane and then compressed maintaining a radial pressure.
In this model, a vertical displacement and a confinement pressure are applied on the sample and the static response and the collapse load for various confinement pressures are studied. The material is modeled with the soil plasticity feature, and the Drucker-Prager criterion. The analysis can be simplified by considering the intrinsic axial symmetry of the model.