Modified Mohr Coulomb

The Modified Mohr-Coulomb model is an advanced material model that can simulate the behavior of different types of soil. It is based on an elasto-plastic formulation and can capture the basic properties of soil material, namely a pressure dependent shear strength (with soil dilatancy), irrecoverable compaction and nonlinear elastic unloading. This leads to a so-called double hardening model:

1. One yield-surface for shear failure and one yield-surface for compaction.

2. The Modified Mohr-Coulomb model combines power-law nonlinear elastic behavior, with exponential cap-hardening with Rowe's dilatancy rule.

3. A parabolic hardening of the friction angle as function of the plastic shear-strain according to Duncan-Chang.

Applicable Modules:

General Parameters

Poisson's Ratio (u)

The ratio of the radial (or lateral) strain to the vertical strain.

Temperature Coeff. (α)

The relative change of a physical property when the temperature is changed by 1 K.

Unit Weight (Υt)

The weight of soil per unit volume.

Saturated Unit Weight (Υsat)

The weight of saturated soil per unit volume.

Cohesion (c)

It is a measure of the forces that cement particles of soil.

Internal Friction Angle (Φ)

It is a measure of the shear strength of soils due to friction.

Earth Pressure Coeff. (Ko)

The ratio of horizontal principal effective stress to the vertical principal effective stress.

Draining Condition

Drained

Dissipation of pore water pressure takes place upon the load application.

Undrained

Dissipation of pore water pressure does not take place upon the load application.

Skempton 'B' Coefficient

Enter the value of the coefficient for an 'Undrained' condition.

Additional Parameters

Secant Stiffness in Tri-axial Test

Modulus of Elasticity for reference pressure in Oedometer test.

Unloading/Reloading Stiffness

Modulus of Elasticity for unloading or reloading section in Oedometer test result.

Index of Power Law

Modulus of Power Law nonlinear elastic model.

Power Law nonlinear elastic model.

Generally, 0.5 is used as the value.

Porosity

Enter the porosity of soil.

Stress Ratio of Normal Consolidation

Enter the stress ratio of normal consolidation

Dilatancy Angle (ψ)

It represents the ratio between a volumetric strain and a shear strain rate. If un-checked, the same value as the Internal Friction Angle is reflected in analysis.

Consider Cap

Activate the Compressive Yield Stress and Cap Coefficient.

Compressive Yield Stress

Enter the compressive yield stress of the soil.

Cap Coefficient

Enter the cap coefficient of the soil.

Safety Factor Calculation (only for Tunnel Module)

The safety factor is calculated on the basis of the ratio of the current state of stress of the material to the Mohr-Coulomb failure criterion.  The Mohr-Coulomb failure criterion is most widely used criterion for brittle materials like ground.  SoilWorks uses the criterion for all the material models in the Tunnel Module.