Case 2 Extension and Compression with Sedimentation

Contents

The present bench scale Case 2a and Case 2b is an elevation of the Case 1 base case to include two different cases of syn-sedimentary growth under extensional and compressional tectonic settings. A single moving sedimentation horizon is used to define three new sedimentation layer horizons. A full data description will not be presented here, only key data different from the base case for Case 2a only will be described. Case 2b is similar but with different displacement and sedimentation loading sequences and associated control data.

The two simulation runs complete in approximately 10 - 12 mins on a 3.6 GHz AMD processor machine.

Mech_005_Case2_02

Problem Description (Dimensions as Case 1)

The two case simulations comprise five stages including three stages with sedimentation with the timings summarized in the table below :

Stage #	Description	Case 2a: Stage duration & Time lapse (hours)	Case 2b: Stage duration & Time lapse (hours)
Stage 1	Geostatic initialization with gravity	0.5 [0 - 0.5]	0.5 [0 - 0.5]
Stage 2	Extension loading	1.7 [0.5 - 2.2]	1.7 [0.5 - 2.2]
Stage 3	Extension and Compression loading + Sedimentation #1	1.0 [2.2 - 3.2]	1.9 [2.2 - 4.1]
Stage 4	Compression loading + Sedimentation #2	0.6 [3.2 - 3.8]	0.7 [4.1- 4.8]
Stage 5	Compression loading + Sedimentation #3	1.0 [3.8 - 4.8]	0.6 [4.8 - 5.4]

The data files for the project are in : Mech_005\Case02\Data.

The following lists the differences in data from the Case 1 base case:

•Adaptivity set #1 to include deposition flag data to accommodate the newly deposited groups.

•Loading data to include extensional and compressional tectonic settings.

•Inclusion of sedimentation data with moving sedimentation horizon for three additional stages of syn-sedimentation growth.

Adaptivity Data

Data File

* Adaptivity_set_data NUM=1

! ---------------------------------

Distortion_area_data IDM=1

Element_sizes IDM=2

/Max. Element Size/ 8.0

/Min. Element Size/ 3.0

Coarsening_type "P_strn"

(...)

Deposition_flag 1

1Inclusion of Deposition_flag data set to 1 for adaptivity set #1 to define that this data is to be used for the newly deposited groups (stratigraphy layers).

Loading Data - Displacement and Sedimentation

•Loading data in this example comprise of extensional and compressional displacements with three syn-sedimentations (denoted by S#) as shown in the graphical plot below.

Mech_005_Case2_01

Case 2a & 2b: Displacement-time curve (blue line) over 5 stages of analysis with 3 sedimentation instances (red S#)

Displacement Loading Data (Case 2a)

Data File

* Time_curve_data NUM=1

! ---------------------------------

Name "Displacement"

Time_curve IDM=7

0.5 2.0 2.3 2.8 3.1 4.0 4.8

Load_factor IDM=7

0.0 37.5 37.5 50.0 50.0 25.25 25.25

* Global_loads NUM=1

! ---------------------------------

Name "Displacement"

Prescribed_displacement IDM=2 JDM=2

/Set 1/ -1 0

/Set 2/ 1 0

Pres_displacement_geom_set IDM=2

"West"

"East"

Pres_displacement_geom_ass IDM=2

1 2

1The displacement-time curve is modified to include both extensional and compressional tectonic settings. Note that the displacement value specified is the load factor multiplied by the prescribed displacement value (which is set at ±1).

Sedimentation and Solution Control Data

Sedimentation data comprise:

•One Sedimentation_horizon data in conjunction with Time_curve_data data to define the moving sedimentation horizons for the three sedimentation instances.

•Three sets of Sedimentation_data data structures to define the sedimentation data for each of the three sedimentation instances.

Sedimentation Horizon Data (Case 2a)

Data File

* Sedimentation_horizon NUM=1

! ---------------------------------

Name "General"

Facet_topology IDM=2 JDM=1

1 2

Coordinates IDM=2 JDM=2

-50.0 140.0

500.0 140.0

Time_curve 1000

Displacement IDM=2

0.0 1.0

* Time_curve_data NUM=1000

! ---------------------------------

Time_curve IDM=4

0.5 2.2 3.2 3.8

Load_factor IDM=4

0.0 10.0 30.0 70.0

1The sedimentation horizon named "General" is defined by a single facet comprising two nodes positioned vertically at the top surface of the initial configuration and moved vertically upwards at different rates following the time curve data #1000 which is defined by four points. Note that the reference displacement is set at 1.0 to simplify multiplication with the load factor.

2The moving sedimentation horizon is targeted for deposition to vertical y-coordinate of:

a.150mm at model time of 2.2 hrs

b.170mm at model time of 3.2 hrs

c.210mm at model time of 3.8 hrs

Sedimentation #1 (Case 2a)

Data File

* Sedimentation_data

! -----------------------------------

Stratigraphy_unit_name "Sand2"

Sediment_horizon_name "General"

Material_name "Sand_1"

Duration 0.8

Output_flag 1

* Control_data

! -----------------------------------

Control_title "Sed1"

Factor_critical_time_step 0.7

Solution_algorithm 1

Maximum_number_time_steps 1E6

Termination_time 3.2 ! Duration 1.0

Output_frequency_plotfile -1

Output_frequency_restart -1

Output_time_plotfile 0.2

Screen_message_frequency 500

1Sedimentation #1 occurs at model time of 2.2 hrs with deposited sediments to sediment horizon at y=150mm over a duration of 0.8 hrs. Note that the sedimentation duration must be set equal or less than the stage duration, which for this stage is 1.0 hrs.

Sedimentation #2 (Case 2a)

Data File

* Sedimentation_data

! -----------------------------------

Stratigraphy_unit_name "Sand3"

Sediment_horizon_name "General"

Material_name "Sand_1"

Duration 0.5

Output_flag 1

* Control_data

! -----------------------------------

Control_title "Sed2"

(...)

Termination_time 3.8 ! Duration 0.6

(...)

1Sedimentation #2 occurs at model time of 3.2 hrs with deposited sediments to sediment horizon at y=170mm over a duration of 0.5 hrs. The stage duration for this sedimentation is set at 0.6 hrs.

Sedimentation #3 (Case2a)

Data File

* Sedimentation_data

! ---------------------------------

Stratigraphy_unit_name "Sand4"

Sediment_horizon_name "General"

Material_name "Sand_1"

Duration 0.8

Output_flag 1

* Control_data

! -----------------------------------

Control_title "Sed3"

(...)

Termination_time 4.8 ! Duration 1.0

(...)

1Sedimentation #3 occurs at model time of 3.8 hrs with deposited sediments to sediment horizon at y=210mm over a duration of 0.8 hrs. The stage duration for this sedimentation is set at 1.0 hrs.