Case 1 Constant Sedimentation Rate

Each stage (step) of the analysis is terminated by a Control_data data structure that defines the solution, output and termination data for the stage.  Multiple stages therefore require multiple Control_data keywords, with the data modifications for each stage defined prior to the Control_data keyword for the stage.  This is demonstrated in the pseudo data file below.

The stratigraphy associated with the initial sediment must be defined when the layer sedimentation procedure is used.  This requires

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).

Stratigraphy_definition

The stratigraphy order is specified in order starting from the deepest sediment layer.  Each stratigraphy layer must comprise a single group (see Group_data). It is recommended that, for each layer,  the stratigraphy unit name, stratigraphy horizon name and group name are identical.  This greatly simplifies data definition and result interrogation, especially when the number of stratigraphy layers becomes large.   If this convention is adopted, ParaGeo will internally identify the required associations between unit, horizons and groups, so that only the unit order is specified on the Stratigraphy_definition data structure.

Stratigraphy_horizon

The stratigraphy horizon defines the top surface of each pre-existing stratigraphy unit.  It is defined by a set of geometry lines in 2-D or a set of geometry surfaces in 3-D. A Stratigraphy_horizon data structure must be defined for each stratigraphy unit.

Layer sedimentation is defined using two data structures:

1Sedimentation_data which defines the control data for deposition of a single layer; e.g. unit name, material, sedimentation type, etc.

2Sedimentation_horizon which defines the target topology for the stratigraphy horizon of the new layer.

Note that a Stratigraphy_horizon is an existing horizon defined by geometry entities (lines 2-D, surfaces 3-D) that form part of the model, whereas a Sedimentation_horizon is a faceted surface that is not connected with the model.   During layer sedimentation new geometry entities are created to define the new layer, and the Stratigraphy_horizon for the new layer is formed using a combination of these new geometry entities and pre-existing geometry (if required).

Sedimentation_Data

Sedimentation_data is the primary data structure for definition of sedimentation of a new stratigraphy unit.    One data structure is required for each new layer and the sedimentation process is associated with a single analysis stage (step).   Consequently in the current problem, where nine additional layers are deposited on the pre-existing layer, the analysis consists of ten steps.  The principal data includes:

1The name of the new stratigraphy layer (Stratigraphy_unit_name).

2The sedimentation horizon name (Sediment_horizon_name); i.e. the Sedimentation_horizon to be used in defining the top surface of the new layer.

3The name of the material properties to be used for the new material (Material_name).

4The duration (Duration) of the initialisation of gravity loading for the new layer.  This is generally set to less than the time for the stage so that additional dynamic relaxation can occur prior to deposition of the next layer.

By default, the Sedimentation_type is "Absolute" where the Sedimentation_horizon defines the top surface of the new layer.  Two alternative sedimentation types are available:

1"Relative" - where a sedimentation horizon defines the topology of the new top surface but its location is defined via a layer thickness (Reference_thickness) and reference location (Reference_location).  The sedimentation horizon is then positioned so the vertical thickness is correct at the reference location.

2"Drape" - Where a uniform thickness of material is added across the complete model.  In this case only the thickness of the layer (Reference_thickness) is required.

Sedimentation_Horizon

The Sedimentation_horizon data structure defines the topology of a top surface horizon for sedimentation of a new stratigraphy layer.  The horizon is defined as a faceted surface; i.e. 2-noded facets in 2-D, 3-noded facets in 3-D.  The  node numbering and coordinates defining the faceted surface are defined in the data structure and do not form part of the nodes in the mesh.  The horizon may be defined as either stationary or moving; e.g. increasing in elevation or prograding, via a displacement component magnitudes and a time curve.   A sedimentation horizon may be used to define more that one layer; e.g. a prograding horizon is often used to define sedimentation of all layers.  Alternatively multiple sedimentation horizons may be specified and used for sedimentation of individual layers.

The Gravity_data data structure identifies that gravity is active in the problem and defines the magnitude of the gravitational constant.  Gravity can  be applied either instantaneously; i.e. with geostatic initialisation, or may be assigned a load curve to allow a gradual increase of gravity with time.   When new layers are sedimented, gravity should be ramped up slowly over the deposition stage.  Depending on the specific application, either a linear ramp or an S-Curve (smoothly varying ramp)  is used.  

When solving problems in metric units the gravitational constant should be specified in m/s2 (even if the units are mm) provided the problem or material units are specified.  If no units are specified then care has to be taken to  define material density and the gravitational constant to be consistent with the geometry definition.

By default the load curve associated with Gravity_data is also used during sedimentation of new layers, but with the Time_curve automatically adjusted based on the sedimentation duration (see Duration on the Sedimentation_data data structure).

Material grids are uniform grids that can be superimposed on the finite element mesh.  Once active, the grid deforms with the mesh and therefore gives an indication of the distortion of the model.   They are particularly useful in visualisation of localised deformation; i.e. shear bands and faults.  They are often defined in the initial configuration but can also be defined part-way through an analysis; i.e. when new material is sedimented.  The compulsory data for Material_grid_set comprises:

1A list of groups, specified by name (Group_names) or number (Groups), for which material grids should be generated.  An individual grid is generated for each group.

2The division size (cell size) for the group.  The division size in the x-direction (Division_size_x) must be specified and by default the division size in the Y-direction is identical.

3The grid origin (Grid_origin) - which in 2-D is the X and Y coordinates of the lower left hand corner of the grid.

The Deposition_flag is also set for the Material_grid_set. This indicates that a new material grid should be created using this data for each newly deposited layer.

Contour values that define stripes when post-processed may also be output, via Stripe_spacing_x and Stripe_spacing_y.   These provide an effective visualisation option that may be displayed with or without the underlying grid in ParaView.  Material grids can be visualized by loading the grid plot file filename_grid.xmf