The initial data file for the project is: SubMod_001\Step1\Data\Submod_001_Step1.dat. The basic data includes:
1Geometry set data for all model boundaries. 2Stratigraphy definition for the two formations present in the model. 3A Stratigraphy_surface_load to define boundary conditions at the top surface. 4Group data for the two formations which are assigned the "Shale_CF75" properties using Group_control_data and Group_data data structures. 5A Material_data structure to read the material properties for the Shale lithology from an external file. 6Data required to define geostatic initialization with a prescribed porosity trend (Geostatic_data, Spatial_variation_definition and Spatial_variation_values ) 7Gravity data (Gravity_data) 8Support data (Support_data) defining fixity in perpendicular directions to each lateral boundary and fixity in vertical direction for the base. 9Load data defining a prescribed displacement on the west boundary which takes place between 0.25 and 0.5 Ma. 10Mesh control (Mesh_control) and Unstructured mesh generation data (Unstructured_mesh_data) defining a constant mesh size of 1000m. 11Damping data (Damping_global_data) to define bulk damping on the effective mean stress (Bulk Viscosity model) 12Time scaling data (Time_scaling_data) with optimal time step 1E-4 Ma. 13History_global data for output of global energy result history (results as a function of time). 14Geostatic_control_data to set the constitutive model as elastic. 15Control data (Control_data) for two stages defining: (a) Incremental solution algorithm (Type 1), (b) Maximum number of time steps of 106 (very large) (c) Duration of t=0.25 Ma, (d) Factor of critical time step = 0.5, (e) Plot file output at the end of the stage, (f)Screen message output every 500 mech steps, (g) Output of a restart file at the end of the stage. 16Geometry data (Nodal_data, Geometry_line, Geometry_surface and Geometry_volume) for definition of the 3D geometry.
The Geometry_set data for each of the boundaries is defined by:
1The name of the geometry set. 2The geometry entities that constitute the geometry set.
Data File
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* Geometry_set NUM=1
Name "West"
Surfaces IDM=2
5 6
* Geometry_set NUM=2
Name "East"
Surfaces IDM=2
2 3
* Geometry_set NUM=3
Name "Base"
Surfaces IDM=1
1
* Geometry_set NUM=4
Name "Top_surface"
Surfaces IDM=1
4
* Geometry_set NUM=5
Name "North"
Surfaces IDM=2
9 11
* Geometry_set NUM=6
Name "South"
Surfaces IDM=2
8 10
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1Six geometry sets for the base, top surface, North, South, East and West boundaries are defined by specification of the corresponding surfaces. |
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The stratigraphy associated with the initial sediment is defined by:
1Defining the existing stratigraphy layer depositional order and the group associated with each layer (via Stratigraphy_definition). 2Defining the topology of the top surface horizon for each stratigraphy layer (via Stratigraphy_horizon). The stratigraphy is defined in a similar way to Mech_002 where is a fuller description is provided.
Note that in simulations where geostatic initialization is performed the definition of the stratigraphy is compulsory.
Stratigraphy_definition
Data File
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* Stratigraphy_definition
Unit_Names IDM=2
"formation1"
"formation2"
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1Two formations present in the initial model. 2The group names coincide with their respective horizon names and unit names, so only the unit order is required.
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Stratigraphy_horizon
Data File
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* Stratigraphy_horizon NUM=1
Name "formation1"
Surfaces IDM=1
7
* Stratigraphy_horizon NUM=2
Name "formation2"
Surfaces IDM=1
4
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1The stratigraphy horizons for "formation1" and "formation2" must be defined.
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A surface load may be defined for the top surface via the Stratigraphy_surface_load data structure. This is usually recommended in coupled problems to prevent the weak sediments near surface to reach positive stresses if pore pressure develops and in some geomechanical only problems to facilitate stabilization of surface slopes and prevent material flow. In coupled problems boundary conditions for pore pressure and/or temperature may also be specified.
Data File
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* Stratigraphy_surface_load
Applied_stress 0.1
Pore_pressure_flag 1
Time_curve_stress 100
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1A top surface load of 0.1 MPa (effective stress) is applied to the column. 2Pore pressure is prescribed at top surface by defining Pore_pressure_flag=1. Because no pore pressure magnitude is provided the prescribed pore pressure at top surface is 0 (note that in this example only the geomechanical field is active). 3The top surface load is ramped up according to the rate defined in the load curve number 100 (synchronous to gravity)
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The Group_data data structure is compulsory and defines the properties for each geometry group. For this example these comprise:
1The name of the group. 2The element type. 3The material assigned to the group 4The volume that defines the geometry for the group. 5The type of porous flow
Data File
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* Group_data NUM=1
Group_name "formation1"
Element_type TET4V
Material_name "Shale_CF75"
Volumes IDM=1
1
Porous_flow_type 5
* Group_data NUM=2
Group_name "formation2"
Element_type TET4V
Material_name "Shale_CF75"
Volumes IDM=1
2
Porous_flow_type 5
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1Two groups are defined using the TET4V (4 noded tetrahedral elements using the average Volume formulation). 2The material assigned to these element groups is "Shale_CF75". 3The geometry of the "formation1" group is defined by volume 1 and "formation2" group by volume 2. 4The simulation will be performed using the porous flow type number 5 (hydrostatic drained assumptions with vertical effective stress calculated using the buoyant density). |
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The Group_control_data data structure is compulsory and defines:
1The groups number of geometry groups in the problem, where each geometry group relates to a region with specific properties; e.g. regions with different material assignments, individual stratigraphy layers, etc. 2Whether the group is active or inactive in the fields; i.e. geomechanical, porous flow, thermal, that are being solved.
Data File
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* Group_control_data
Group_numbers IDM=2
1 2
Active_geomechanical_groups IDM=2
1 1
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Two groups are present in the simulation with the geomechanical active.
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The material properties for the material "Shale_CF75" are defined in a separate file named Shale.mat. The Material_data structure is used to specify the material and material file names.
Data File
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* Material_data NUM=1
Material_name "Shale_CF75"
Material_file "Shale.mat"
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1A single material is used for the simulation. 2The material is named "Shale_CF75". 3The material properties are defined in Shale.mat file (which should be placed in the same folder as the main model datafile).
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Data for geostatic initialization is defined in the same manner as in the tutorial example geost_001 Initialization of a 3000m 3D column. Full description of the data is provided in Case 1 Base Case description.
Additionally, in this example a Geostatic_control_data data structure enforcing elastic constitutive model is included. This data structure is placed before the control stage in the Submod_001_Step1.dat datafile.
Geostatic_data
Data File
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* Geostatic_data NUM=1
Groups IDM=2
"formation1"
"formation2"
Porosity_spatial 1
Pore_pressure_distribution "Hydrostatic"
Time_curve 100
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1The geostatic data is applied to the two groups. 2The initial porosity distribution for geostatic initialization will be defined using the Spatial_variation_definition number 1. 3The initial pore pressure distribution will follow an hydrostatic gradient. 4Geostatic initialization will be performed according to the rate described in the time curve number 100 (i.e. synchronous to gravity application. This is generally recommended).
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Spatial_variation_definition
Data File
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* Spatial_variation_definition NUM=1
Description "Porosity vs. Depth"
Type "Absolute"
Distribution "Depth_dependent"
Variation_assignment 1
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1A brief description (164 characters max.) is provided to facilitate identification of the data defined by the spatial variation. 2The type of spatial variation is defined as "Absolute" (i.e. the spatial variation values are absolute values for defining porosity) . 3The distribution is depth dependent (i.e. the spatial variation values will define porosity as a function of depth). 4The Spatial_variation_values data structure number 1 is assigned to define the porosity vs depth trend for initialization. |
Spatial_variation_values
Data File
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* Spatial_variation_values NUM=1
Description "Normal Compaction Trend"
Time 0.0
Values_vs_depth IDM=35 JDM=2
0 179.3 ... 6097.4
0.48834 0.44717 ... 0.039523
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1A brief description (164 characters max.) is provided to facilitate identification of the data defined by the spatial variation values. 2The time associated for the definition of the porosity values is set to 0.0 (i.e. from the beginning of the simulation). 3The porosity trend with depth is defined by two rows of 35 depth-ordered values containing: aRow 1: Depth values bRow 2: Porosity values |
Gravity_data and associated Time_curve_data
Data File
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* Gravity_data
Gravity_constant 9.810
Load_curve 100
* Time_curve_data NUM=100
Curve_type 2
Time_curve IDM=2
0.0 0.25
Time_factor IDM=2
0.0 1.0
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1The gravity constant is defined (9.81 m/s2). 2The time curve number 100 is assigned to define the rate for gravity application. 3The curve type is set to 2 (i.e. an S-shape curve). 4The time curve is defined by two points in such a way so that from time 0.0 to time 0.25 gravity should be gradually applied following an S-shape function. |
Geostatic_control_data
Data File
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* Geostatic_control_data NUM=1
Stress_constitutive_model "Elastic"
Stress_initialisation_type "Standard"
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An elastic constitutive model is enforced and stress initialization will be performed according to data in Geostatic_data.
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The support data is used to define the directions which have a prescribed displacement (in absence of a displacement defined via Global_loads the prescribed displacement is zero, i.e. fixity).
Data File
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* Support_data
Displacement_codes IDM=3 JDM=4
1 0 0
0 1 0
0 0 1
1 1 1
Displacement_code_geom_set IDM=5
"North"
"South"
"East"
"West"
"Base"
Displacement_code_geom_ass IDM=5
2 2 1 1 3
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1All surfaces are prescribed displacement to their respective perpendicular directions (except top surface which is free to move).
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A compressive tectonic load (displacement) on the West boundary is defined to occur between 0.25 and 0.5 Ma.
Data File
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* Time_curve_data NUM=1
Time_curve IDM=11
0.0 0.25 0.263 0.275 ... 0.5
Load_factor IDM=11
0.0 0.0 0.0038 0.0152 ... 1.0
* Global_loads NUM=1
Prescribed_displacement IDM=3 JDM=1
3000 0 0
Pres_displacement_geom_set IDM=1
"West"
Pres_displacement_geom_ass IDM=1
1
* Load_case_control_data
Loadcases IDM=1
1
Active_load_flags IDM=1
2
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1A compressive load in the X direction is prescribed to western boundary. The displacement magnitude is defined to be 3000m (15% of the model length). 2The load is ramped up gradually following a non-lineal function (starts at low rate and then rate smoothly increases). 3The load is defined as being active in the Load_case_control_data (flag 2). |
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An "unstructured mesh" with 1000m size tetrahedral elements is defined for this example.
Data File
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* Mesh_control_data
Generation_algorithm 2
Mesh_generation_flag 0
* Unstructured_mesh_data
Default_element_size 1000
Element_size_bounds IDM=2
1000
/ 1000
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1The algorithm used for this simulation is set to 2 (i.e. unstructured mesh). 2The mesh generation flag is set to 0 so analysis will be performed after mesh generation (default). 3The element size is set to 1000 m.
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Bulk viscosity damping is defined in order to damp the compression part of the dynamics-related oscillations on the effective mean stress.
Data File
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* Damping_global_data
Percentage_damping 0.02000
Bulk_damping_model "BulkViscosity"
Bulk_damping_properties IDM=1
0.50000
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A bulk viscosity model with a bulk viscosity constant of 0.5 is used in this example in order to damp the compressive oscillations due to dynamics in the effective mean stress. This is a generally recommended set up for most of ParaGeo geomechanical analysis. (For more information on the bulk viscosity model see Damping_global_data).
Note that despite percentage of damping is defined this will not be active as percentage damping and bulk damping are mutually exclusive and the later has preference.
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The mechanical step size is defined via Time_scaling_factors data structure. The Optimal_time_step keyword has been used. It is the most simple way of defining the mechanical time step size and is generally recommended. Using this method the mass scaling is computed automatically.
Data File
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* Time_scaling_factors
Optimal_time_step 1.0E-04
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An optimal time step of 5.0·10-5 Ma is defined
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The History_global data structure is used to output global energy data.
Data File
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* History_global
Output_frequency_time 0.05
Mech_global_energy_data IDM=2
"Kinetic" "Elastic"
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Output of Kinetic and Elastic energy data is requested every 0.05 Ma
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The current analysis considers two identical control stages defined by the Control_data structure in which control data for the geomechanical fields is provided. For more information see Solution Control Data.
Data File
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* Control_data
Control_title "Gravity"
Solution_algorithm 1
Maximum_number_time_steps 1000000
Duration 0.25
Factor_critical_time_step 0.5
Output_frequency_plotfile -1
Screen_message_frequency 500
Output_frequency_restart -1
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1Duration for control stages is set to 0.25 Ma is defined. 2The solution algorithm is set to number 1, i.e. Transient dynamic algorithm. 3The maximum number of time steps is set to 106. 4The factor critical time step is set to 0.5 so the time step used for the simulation will be 0.5 · 1·10-4. 5Information will be displayed on the screen (command prompt) every 500 mech steps. 6A plot file is requested at the end of the stage (Output_frequency_plotfile=-1). 7Output of a restart file is requested at the end of the control stage. |
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A summary of the data for defining the 3D geometry for this example is presented bellow. These data comprise Nodal_data, Geometry_volume, Geometry_surface and Geometry_line data structures.
Nodal_data
Data File
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* nodal_data
node_number IDM=12
1 2 3 4 5 6 7 8 9 10
11 12
coordinates IDM=3 JDM=12
0 0 0
20000 0 0
20000 0 2500
20000 0 4000
0 0 5000
0 0 2500
0 12000 0
20000 12000 0
20000 12000 2500
20000 12000 4000
0 12000 5000
0 12000 2500
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1All the nodes that will be used to define geometry lines are defined here. 212 nodes are required to define the geometry. 3In 3D problems coordinate Z is for the vertical direction (height/depth).
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Volumes
Data File
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* geometry_volume NUM=1
Surfaces IDM=6
1 2 7 6 8 9
* geometry_volume NUM=2
Surfaces IDM=6
7 3 4 5 10 11
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Two volumes formed by 6 surfaces each define the geometry of the problem.
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Surfaces
Data File
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* geometry_surface NUM=1
surface_type 5
lines IDM=4
1 16 8 15
* geometry_surface NUM=2
surface_type 5
lines IDM=4
2 17 9 16
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* geometry_surface NUM=11
surface_type 5
lines IDM=4
14 10 11 12
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1Eleven surfaces are defined. 2Each surface is defined by four lines.
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Lines
Data File
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* geometry_line NUM=1
line_type 1
points IDM=2
1 2
* geometry_line NUM=2
line_type 1
points IDM=2
2 3
.
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* geometry_line NUM=20
line_type 1
points IDM=2
6 12
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1Twenty lines are defined. 2Each line connect two nodes.
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