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Material Properties
Strength and elastic properties of materials (rock or soil) are entered in the Define Material Properties dialog. If you are considering groundwater in your model, then the material hydraulic properties are entered in the Define Hydraulic Properties dialog. Material properties are assigned to different regions of the model with the Assign properties option.
Define Material Properties dialog
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Material Properties: Strength Parameters
The following material strength models are available in Phase2:
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Mohr-Coulomb
Hoek-Brown (original criterion)
Generalized Hoek-Brown (latest version)
Drucker-Prager
Cam-Clay
Modified Cam-Clay
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If you set the Material Type = Elastic, then the material is assumed to have unlimited strength (i.e. it will not yield or fail). The material response will be linear elastic, regardless of the stress magnitude. You may still define strength parameters, but they will only be used for the calculation of strength factor (i.e. degree of overstress).
If you set the Material Type = Plastic, then the material can yield and exhibit non-linear stress-strain behaviour, if the stress exceeds the strength envelope. For Mohr-Coulomb, Hoek-Brown and Drucker-Prager models, you may specify peak and residual strength parameters. Residual strength will be applied if the peak strength is exceeded. If residual = peak, this defines an elastic-perfectly plastic material. If residual strength = 0 this defines a brittle material.
Mohr-Coulomb strength parameters
Hoek-Brown Strength Parameters
Generalized Hoek-Brown Strength Parameters
Drucker-Prager Strength Parameters
Cam-Clay Strength Parameters
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Material Properties: Elastic Parameters
The following elastic models are available in Phase2:
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Isotropic
Transversely Isotropic
Orthotropic
Duncan-Chang Hyperbolic
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By default in Phase2, materials are assumed to have Isotropic elastic properties. This means that the elastic properties are not dependent on directionality, and are defined by a single value of Young's modulus and a single value of Poisson's ratio.
Isotropic elastic parameters
In special cases, you may wish to define a material with different elastic properties in two directions (Transversely Isotropic) or three directions (Orthotropic). However, if you use either of these two options, then it is NOT possible to define non-linear material strength properties (i.e. the material stress-strain response will be linear elastic).
Transversely isotropic elastic parameters
Orthotropic elastic parameters
Duncan-Chang Hyperbolic elastic parameters
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Material Properties: Parameter Calculator
For the Generalized Hoek-Brown strength criterion, a special parameter calculator is available by selecting the GSI button. This allows you to estimate the Hoek-Brown parameters mb, s and a, from the rock mass parameters GSI, mi and D, using the dialog shown below. The rock mass elastic modulus can also be estimated.
GSI calculator option
Generalized Hoek-Brown parameter calculator
From the parameter calculator dialog, assist dialogs are available to help with the selection of values for UCS, GSI, mi and D. These are accessed by selecting the Pick button beside the input parameter edit box.
GSI assist dialog
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Material Properties: Link to RocData / RocLab
If you have the programs RocData or RocLab installed on your computer, you can start up these programs directly from the Define Material Properties dialog. You can use RocData or RocLab to help determine parameters for the Mohr-Coulomb, Hoek-Brown or Generalized Hoek-Brown criteria (e.g. by curve fitting lab test data, for example).
Link to RocData from Phase2 material properties dialog
You can paste results from RocData into Phase2, by selecting the Paste button in the material properties dialog.
RocData analysis results
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Material Properties: Staging
The properties of a material can be modified at different stages of a multi-stage model, by using the Stage Properties option in the Define Material Properties dialog. Any of the material parameters can be increased or decreased by user-defined factors at different stages. This allows the user to simulate changes in material stiffness or strength (for example) as staging progresses.
To stage material properties, select the Stage Properties checkbox and select the Define Factors button.
Multiplication factors can be defined for any material property at any stage, in the Stage Material Properties dialog. For example, as shown below for Young's Modulus.
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Material Properties: Datum Dependent
The Datum Dependent option allows you to define material properties which vary linearly with depth from a user-defined datum elevation. The following properties can be specified as Datum Dependent:
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Young's Modulus (only if the material Elastic Type = Isotropic)
Cohesion and Friction Angle (only if Failure Criterion = Mohr-Coulomb and
Material Type = Plastic).
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To define Datum Dependent properties, select the Datum Dependent checkbox and select the Define Properties button.
Datum Dependent Properties dialog
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Material Properties: Hydraulic
The Define Hydraulic Properties option is used to specify the groundwater/hydraulic parameters for each material in the Define Material Properties dialog.
Define Hydraulic Properties is applicable if you are considering pore pressure in your Phase2 model (i.e. Piezometric Lines, Water Pressure Grid, Ru values, or finite element seepage analysis).
Define Hydraulic Properties (Groundwater Method = Piezometric Lines)
If the Groundwater Method = Finite Element Analysis, then you can define the saturated permeability, anisotropic parameters, and the unsaturated permeability function. You may choose from several different theoretical models, or enter a user-defined permeability function (i.e. Matric suction versus Permeability). Hydraulic Properties can also be staged.
Define Hydraulic Properties (Groundwater Method = Finite Element Analysis)
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Material Properties: Assign
If your model has multiple materials, then the properties are assigned to the desired regions with the Assign Properties option. This is done graphically with the Assign Properties dialog. Just select a material in the dialog, then click within any closed region of the model, and the region will be assigned the selected material type. Material removal (i.e. excavation) is also accomplished with the Assign option.
Select a material type in the Assign dialog
Click the mouse in the model to assign the material to a region
Material assignment or excavation can also be done with the right-click menu.
Assigning materials with the right-click shortcut
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