Geostatic_control_data
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Data Structure: Geostatic_control_data |
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Geostatic control Data structure |
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Geostatic_control_data NUM=ival where ival is the data structure number |
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Overview Geostatic control facilities: •Multi-step geostatic initialization where in each step specific assumptions can be applied, particularly related to the material and contact models. •Specification of additional initialization options; e.g. re-initialisation of displacement and state variables after establishing geostatic equilibrium.
Geostatic control may be used for cases where the initial geostatic state cannot be fully defined a-priori or when additional initialization options are required. For example, when discrete contact surfaces are present two situations can arise: •The displacement associated with establishing contact stress results in horizontal stresses that differ significantly from the target values, in which case an additional initialization step can be used to improve these values •Undesirable plastic deformation is observed adjacent to the contact surfaces during initialization. This can be ameliorated by performing the initial geostatic step using an elastic material assumption then performing an additional step where there is a gradual transition to nonlinear response. •Undesirable slip or de-bonding occurs on the contact surfaces. In this case setting the contact model as elastic in the first step and then performing a subsequent step with a gradual transition to slip assumptions may be beneficial.
Stress Initialisation The stress initialisation options are set using: •Stress_constitutive_model, which defines whether the material should be elastic, poroelastic or the standard specified material model. •Stress_initialisation_type, which defines how the forces due to the stresses should be represented.
Contact Initialisation Contact properties can be optionally set using Contact_constitutive_model to: •"Elastic" - (no slip or separation) during geostatic initialisation. In this case the contact is assumed fully bonded; i.e. compression, tangential and adhesion are all set to contact property type 1. •"NoSlip" - (no slip) during geostatic initialisation. In this case the contact is assumed bonded tangentially but separation of the surfaces is permitted. If either condition is used then an additional geostatic step is required where Contact_constitutive_model is set to "Standard" and Contact_initialisation_type is set to "Release".
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 | Set_name Name of the geostatic control data structure |
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Name of geostatic control Set.
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| Include_set_name Name of the geostatic control data structure in the set file |
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Name of geostatic control Set.
Notes •If a set file exists for geostatic data it will be automatrically scanned for this set and if defined the associated data will be imported
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| Set_file_name File containing output set data |
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File containing output set data without directory path (maximum 64 characters). The default geostatic set file name is "geostatic.set".
Notes •The default data is stored in set data directory which is specified using the Set_file_directory keyword on the Settings data structure. •If the file exists in the current directory then it will be used in preference to the default data •If "geostatic.set" exists in the current directory then it will be used by default if Output_data is not specified in the data file.
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| Set_file_read_flag File containing output set data |
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Flag denoting whether the set file should be searched. Valid settings are: • 0 - Do not search and read set file • 1 - Search and read set file (default)
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| Description Description for control data |
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Description for control data (Maximum 128 characters)
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| Stress_constitutive_model Constitutive model for stress initialisation model |
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Stress_constitutive_model can be used to define that the element constitutive model for this geostatic initialisation stage. The valid options are: • "Elastic" - Linear elasticity • "Poroelastic" - Poroelasticity (if defined) • "Standard" - Use model defined in data file (Default)
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| Viscoplasticity_model Viscoplasticity constitutive model for stress initialisation model |
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Viscoplasticity_model specifes how viscoplastic models should be represented when Stress_constitutive_model is either "Elastic" or "Poroelastic". By default viscoplasticity models are unchanged ("Standard") but they also may be set as "Elastic". The valid options are: • "Elastic" - Linear elasticity • "Standard" - Use model defined in data file (Default)
Notes •Viscoplasticity_model has no effect unless Stress_constitutive_model is either "Elastic" or "Poroelastic" •If Stress_constitutive_model is set to "Standard" it will override the Viscoplasticity_model settings for the corresponding materials
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| Embedded_fracture_model Embedded fracture constitutive model for Embedded Fracture |
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Embedded_fracture_model can be used to specify how embedded fractures are represented when Stress_constitutive_model is either "Elastic" or "Poroelastic". By default embedded fractures models are unchanged ("Standard") but they also be set as "Elastic", in which case there influence is not considered during the geostatic step The valid options are: • "Elastic" - Linear elasticity • "Standard" - Use model defined in data file (Default)
Notes •Embedded_fracture_model has no effect unless Stress_constitutive_model is either "Elastic" or "Poroelastic" •If Stress_constitutive_model is set to "Standard" is specified it will override the Viscoplasticity_model settings for the corresponding materials
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| Stress_initialisation_type Defines the mode of stress initialisation for the geostatic initialisation stage. |
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Stress_initialisation_type defines the mode of stress initialisation. The valid options are: • "Standard" - Starting from zero stress apply stress using data defined in the geostatic data structures (Default) • "None" - Ignore the data for stress initialisation in the geostatic data structures • "Update" - Apply the difference between the target stress state defined in the geostatic data and the actual stress state at the end of the last step. • "Release_current" - Gradual transition from elastic material models to nonlinear consititutive models (see description below) • "Release_ramp" - Gradual transition from elastic material models to nonlinear consititutive models (see description below)
Release current If the material was previously set to elastic ( Stress_constitutive_model "Elastic") then a gradual transition from an elastic state to a nonlinear state will be performed in this geostatic stage by: 1 - Saving the internal forces due to the current elastic stress 2 - setting the material as nonlinear, 3 - performing a nonlinear stress update based on the current stress state, 4 - gradually relaxing the internal forces from the elastic stress state to the nonlinear stress state Consequently, with this method the stresses are gradually ramped up from zero.
Release ramp If the material was previously set to elastic ( Stress_constitutive_model "Elastic") then a gradual transition from an elastic state to a nonlinear state will be performed in this geostatic stage by: 1 - Saving the internal forces due to the current elastic stress 2 - Creating an initial stress data structure with the current elastic stress 3 - setting the material as nonlinear, 4 - Zeroing the current stress and applying the initial stress and internal forces using an increasing and decreasing ramp respectively over the stage Consequently, with this method the stress state is not returned to zero.
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| Contact_constitutive_model Contact initialisation model |
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Contact_constitutive_model can be used to define that the contact constitutive model for this geostatic initialisation stage. The valid options are: • "Elastic" - Elastic contact (No slip or separation, sometimes denoted "Tied Contact") • "No_slip" - No tangential slip but separation may occur • "Standard" - Use model defined in data file (Default) • "Adhesive_slip" - No separation but allow slip using standard constitutive model
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| Contact_initialisation_type Defines the mode of contact initialisation for the geostatic initialisation stage. |
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Contact_initialisation_type defines the mode of contact initialisation. The valid options are: • "Standard" - Standard contact with geostatic stress ramped up from zero stress (Default) • "Release" - If the contact model was previously set to elastic ( Contact_constitutive_model "Elastic") then a gradual transition from an elastic state to a nonlinear state will be performed in this geostatic stage.
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| Contact_flow_model Contact flow model for initialisation |
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Contact_flow_model may be used to define different contact porous flow model/properties during the current geostatic initialisation stage; e.g. increasing or decreasing the fault conductivity during the initialisation process. The valid options are: • "Constant" - Constant normal and tangential flow model using values defined by Flow_properties_geostatic • "Standard" - Use model defined in data file (Default)
Note that if Contact_flow_model is set as 'Constant' for a given stage, definition of Contact_flow_model as 'Standard' in a following stage will be required in order to switch to standard model/properties. |
| Contact_thermal_model Contact thermal model for initialisation |
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Contact_thermal_model can be used to define that the contact thermal model for this geostatic initialisation stage; e.g. increasing or decreasing the fault thermal conductivity during the initialisation process. The valid options are: • "Constant" - Constant normal flow using values defined by Thermal_properties_geostatic • "Standard" - Use model defined in data file (Default)
Note that if Contact_thermal_model is set as 'Constant' for a given stage, definition of Contact_thermal_model as 'Standard' in a following stage will be required in order to switch to standard model/properties. |
| Displacement_reinit_flag Model for vertical displacement initialisation during geostatic initialisation |
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Displacement re-initialisation can be used to remove the majority of the displacement that occurred during geostatic initialization. It is performed by restoring the geometry of the model to the original configuration. Special treatment is applied at contact points to modify the geometry to ensure that the contact stresses are approximately unchanged before and after re-initialisation. Re-initialising the displacement may result in small imbalances in internal and external force and therefore requires an additional geostatic stage (step). The number of time steps required in this step is generally small.
Valid model values for vertical displacement initialisation during geostatic initialisation are: • 0 - No displacement initialisation (Default) • 1 - Initialise displacement (coordinates and state variable) at the start of the stage and enforce a gradual transition to the stress and pore pressure states calculated from previous stage. • 2 - Initialise displacement (coordinates and state variable) at the start of the stage. Re-initialise displacement state variable at the end of the stage. Re-initialise displacement coordinates for the top surface. Note that the displacement variable reset is done after the plot file output • 3 - Initialise displacement (coordinates and state variable) at the start of the stage. Re-initialise displacement state variable at the end of the stage. Note that the displacement variable reset is done after the plot file output at the end of the stage. • 4 - Initialise displacement state variable at the end of the stage while keeping the displaced coordinates. Note that the displacement reset is done after the plot file output at the end of the stage.
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| State_reinit_flag Flag to re-initialise element state variables after initialisation |
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Re-initialisation of the element state variables will re-initialise any cumulative state variables that do not directly control the yield surface size. 'Release' should be performed to allow a gradual application of the modified forces. The re-initialisation occurs after creating the end-of-stage plot file so the actual state variables at the end of initialisation may be visualised. Valid values are: • 0 - no re initialisation • 1 - re initialise state variables (default)
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| Time_curve Time curve name or number |
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Specifies the time curve name or number to be used in setting the initial geostatic state. If no time curve is assigned then either a linear ramp or the time curve specified on Geostatic_data will be assumed where appropriate
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| Pre_consolidation_flag Pre consolidation pressure flag |
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The Pre_consolidation_flag can be used to ensure that no-softening of the pre consolidation pressure occurs during geostatic initialisation. In this case plastic yielding on the shear side of the critical state line is permitted, but does not cause a reduction in pc. Valid values are: • 0 - A reduction in pre consolidation pressure due to dilational plasticity is permitted • 1 - Pre consolidation pressure is only permitted to increase due to plastic yielding (default)
Notes •If Pre_consolidation_flag is specified in Geostatic_data for individual groups then this value will be used in preference to the value specified in Geostatic_control_data.
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| Porosity_reinit_flag Flag defining whether porosity should be reinitialised after displacement reinitialisation |
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Flag defining whether porosity should be reinitialised after displacement reinitialisation. Valid values are: • 0 - Do not reinitialise porosity • 1 - Reinitialise porosity (default)
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| Poroelastic_init_flag Flag defining whether the poroelastic constants should be set using the approximate end of step |
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The poroelastic constants are generally dependent on the effective mean stress. This flag optionally allows the value of the constants to be optionally evaluated using the approximate end of step stresses during the initialisation process. During initialisation there is a linear transition to the actual effective mean stress so that at the end of the initialisation process the values are solely dependent on the actual stress. • 0 - Do not use end-of-step stresses to set poroelasticity constants • 1 - Use end-of-step stresses to set poroelasticity constants
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| Fracture_reinit_flag Flag defining whether the state of embedded fractures should be reinitialised after geostatic in |
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Flag defining whether the state of embedded fractures should be reinitialised after geostatic initialisation. Valid values are: • 0 - Do not reinitialise embedded fractures • 1 - Reinitialise embedded fractures at start of stage • 2 - Reinitialise embedded fractures at start and end of stage • 3 - Reinitialise embedded fractures at end of stage
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| Elastic_materials List of Materials by name to be set as elastic for geostatic control step |
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List of Materials by name to be set as elastic for geostatic control step
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| Poroelastic_materials List of Materials by name to be set as poroelastic for geostatic control step |
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List of Materials by name to be set as poroelastic for geostatic control step
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| Standard_materials List of Materials by name to be set as standard for geostatic control step |
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List of Materials by name to be set as standard for geostatic control step
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