Material - Modified Mohr-Coulomb
Introduction To initialize stresses much more efficiently use one of the following methods: 1. Use the Prestress load in the initial stage together with the self weight load. 2. Use elastic materials in the initial stage together with the self weight load and possibly the K0 procedure. Then change the materials to MMC in consecutive stages. The internal variables of the MMC model will be properly initialized in the second stage based on the value of the initial stresses. The shape of the plastic cap (controlling the compaction hardening) is now depending on the value of the Knc ratio (K0 under normal consolidation conditions). Notably, this allows capturing appropriately the reduction of mean effective stress observed when subjecting undrained soft clay samples to shear loading. Parameters Poisson ratio Constant Poisson ratio used in non-linear elasticity Unit weight (Gamma) Density above water level Unit weight (Saturated) Density below water level Cohesion Cohesion at shear failure Friction Angle (Phi) Initial friction angle. Can be chosen close to zero, this friction angle must be smaller or equal to the friction angle at shear defined below. This friction angle controls the onset of shear hardening. If it is chosen equal to the friction angle at shear, no shear hardening will occur (elastic-perfectly plastic in shear) Ko: Stress ratio used during Ko procedure (when selected in analysis options) to correct the horizontal stresses at the end of stress initialization phase. If you chose a value of Ko that is not compatible with the critical state defined by the cohesion and the friction angle at shear, the resulting stress field will satisfy the critical state condition instead of the specified Ko. Secant Stiffness in Tri-axial Test (E50ref) Secant Stiffness in Tri-axial test (E50ref) = Secant Young’s modulus at 50% of shear failure in a triaxial test carried out under reference pressure, Pref <Definition of E50 of Tri-axial Test> Tangential Stiffness Primary Oedometer Test Loading (Eoedref) Tangential oedometer modulus at reference pressure, Pref Unloading / Reloading Stiffness (Eurref) Unloading-reloading Young’s modulus at reference pressure, Pref Reference Pressure Reference Pressure during Tri-axial Test Ultimate Dilatancy Angle Dilatancy angle at shear failure. Friction Angle at shear failure Ultimate friction angle reached when the soil is in critical state (perfect shear plasticity) Power of Stress Level Dependency The elastic bulk modulus is a power law function of the mean effective stress Power law nonlinear elastic model Generally, it uses 0.5. Porosity Initial porosity Knc Ko ratio for normally consolidated soil. You can assess it by default with the Jacky formula: 1 &endash; sin(friction angle at shear). Specifying lower values than the Jacky formula might produce some instability. Forced Normal Consolidation -This option is currently disabled.

Material - Modified Mohr-Coulomb

Introduction

To initialize stresses much more efficiently use one of the following methods:

1. Use the Prestress load in the initial stage together with the self weight load.

2. Use elastic materials in the initial stage together with the self weight load and possibly the K0 procedure. Then change the materials to MMC in consecutive stages. The internal variables of the MMC model will be properly initialized in the second stage based on the value of the initial stresses.

The shape of the plastic cap (controlling the compaction hardening) is now depending on the value of the Knc ratio (K0 under normal consolidation conditions). Notably, this allows capturing appropriately the reduction of mean effective stress observed when subjecting undrained soft clay samples to shear loading.

Parameters

Poisson ratio

Constant Poisson ratio used in non-linear elasticity

Unit weight (Gamma)

Density above water level

Unit weight (Saturated)

Density below water level

Cohesion

Cohesion at shear failure

Friction Angle (Phi)

Initial friction angle. Can be chosen close to zero, this friction angle must be smaller or equal to the friction angle at shear defined below.

This friction angle controls the onset of shear hardening. If it is chosen equal to the friction angle at shear, no shear hardening will occur (elastic-perfectly plastic in shear)

Ko:

Stress ratio used during Ko procedure (when selected in analysis options) to correct the horizontal stresses at the end of stress initialization phase.

If you chose a value of Ko that is not compatible with the critical state defined by the cohesion and the friction angle at shear, the resulting stress field will satisfy the critical state condition instead of the specified Ko.

Secant Stiffness in Tri-axial Test (E50ref)

Secant Stiffness in Tri-axial test (E50ref) = Secant Young’s modulus at 50% of shear failure in a triaxial test carried out under reference pressure, Pref

Tangential Stiffness Primary Oedometer Test Loading (Eoedref)

Tangential oedometer modulus at reference pressure, Pref

Unloading / Reloading Stiffness (Eurref)

Unloading-reloading Young’s modulus at reference pressure, Pref

Reference Pressure

Reference Pressure during Tri-axial Test

Ultimate Dilatancy Angle

Dilatancy angle at shear failure.

Friction Angle at shear failure

Ultimate friction angle reached when the soil is in critical state (perfect shear plasticity)

Power of Stress Level Dependency

The elastic bulk modulus is a power law function of the mean effective stress

Power law nonlinear elastic model

Generally, it uses 0.5.

Porosity
Initial porosity

Knc

Ko ratio for normally consolidated soil. You can assess it by default with the Jacky formula: 1 &endash; sin(friction angle at shear).

Specifying lower values than the Jacky formula might produce some instability.

Forced Normal Consolidation

-This option is currently disabled.