Introduction to Plaxis 3D

Ronald BrinkgrevePlaxis bv

Plaxis 3D Input

Model explorer

Selection explorer

Command line

Mode toolbar

Mode switchesGeneral toolbar

Drawing area

Plaxis 3D Input : Modes

Creation of the FE mesh

MESH

Definition of pressuredistribution

WATER LEVELS

Definition of construction stages

STAGED CONSTRUCTION

Definition of soil stratigraphy

SOIL

Definition of structuralelements, loads

and boundary conditions

STRUCTURES

Model and Selection explorer

• The Model Explorer provides a graphical overview ofthe complete model and the objects that it contains.

• The Selection Explorer provides the samefunctionality as the Model Explorer, but only for thecurrent selection of objects

• For managing any objects created in the model:– shows number of materials, loads– Showing, hiding or deleting model items– Renaming model items– Changing properties of model items

(load values, water height, material sets, …)

Command line• All the actions carried out using either the mouse or the explorers are

translated into commands.• Alternatively, PLAXIS 3D allows to carry out actions using keyboard

input by directly typing the corresponding commands in the commandline.– The Session tab displays the commands executed in the active session– The Model history tab displays all the commands executed in the project

Other functionality• Selection by either clicking individual objects or at once by defining a selection

box in the draw area. Criteria can be applied to the type of items to beselected.

• Group creation for fast model creation when the same operations have to beundertaken over a large number of objects

Soil Mode

Soil mode• Definition of soil volumes and initial water levels• Based on the concept of boreholes• Offers import geometry facilities• Boreholes

– Locations in the draw area where theinformation on soil layering and location ofthe water table is specified

– For multiple boreholes, PLAXIS 3D willautomatically interpolate the soil layersbetween boreholes

– Each defined soil layer is used throughoutthe whole model.

Borehole 1

Borehole 2

Borehole 4

Borehole 3

Borehole definition• Defining soil layer heights in the Soil

layers tabsheet• Defining water conditions in the

Water tabsheet:– Specific Head– Hydrostatic distribution,– Interpolate from adjacent layers– Dry– User-defined pore pressures

• Defining Initial Soil conditions in theInitial conditions tabsheet– Specify OCR, POP, K0x and K0y for

the K0 procedure

Material Sets

• Definition of material sets andparameters for representing the soillayers and structural elements

• Same method of input as Plaxis 2D

Structure Mode

Defining the geometry• Points

– Generated by clicking the Create point button.– Used for Point loads, Point prescribed displacements and Fixed-end

anchors.• Lines

– Generated by clicking the Create line button.– Used to define Beams, Line loads, Line prescribed displacements, Node-to-

node anchors and Embedded piles.• Surfaces

– Generated by clicking the Create surface button.– Used to define Plates, Geotextiles, Interfaces and Surface loads.– The first three created points define the surface plane by default.– Existing surfaces can be edited from the Surface points dialog box of from

the pop-up submenu of Create surface button

• Generate multiple copies of a selection, arranged in a rectangular pattern

Defining the geometry: Array

Defining the geometry: Extrude• Extrusion of Lines and surfaces in order to create surfaces and volumes

respectively:– From the Extrude dialog box– By dragging and dropping the bottom surface to the top surface location

Defining the geometry: Other functions• Decompose into surfaces: creates outer surfaces of selected volumes

• Decompose into outlines: creates contour of selected surfaces

• Intersect: splits selected geometric objects along their intersection

• Combine: merges selected geometric objects of the same kind

• These functionalities are only accessible from the RMB context menu ointhe draw area

Loads

Point load

Line load

Surface load

• Generated by clicking the Create load button or by right-clicking onany geometric objects in the draw area

→ In a similar way it is possible create Prescribed displacements.

Default Boundary Conditions

• Default boundary conditions are– All displacements fixed for the

bottom surface of the soil contour– Perpendicular displacement fixed

for lateral surfaces of the soilcontour

Default boundary conditions can beoverwritten by specifyingPrescribed displacement surfaceson the soil contour

→

Structures

Fixed-end anchor

Beam

Node-to-node anchor

Embedded pile

Plate

Geogrid

Positive interface

Negative interface

• Generated by clicking the Structurebutton

• Can also be created by right-clicking onselected:– points

(fixed-end anchor)– lines

(beam, node-to-node anchor orembedded pile)

– surfaces(plate, geogrid, interfaces)

Importing Geometry• Possibility to import from external sources in different formats like

– 3D Studio files (*.3DS)– AutoCAD native (*.DWG)– Interchange (*.DXF) file format

– Click to import surface

– Click to import volume

The Mesh Mode

Mesh density in Plaxis 3D• Global coarseness:

– Defines an average element size based on model dimensions and relativeelement size factor Re (Very coarse / Coarse / Medium / Fine / Very Fine)

– Reference element size = 0.05 * Re * (Model diagonal length)• Local refinement (Fineness factor):

– Element size can be locally refined or coarsened– Element size = (Fineness factor) * (Global coarseness) * (Ref. elem. size)

• Color code– Depending on their degree of local refinement, geometric objects are

displayed in different color in the Draw area (gray for Fineness factor of 1and green otherwise with darker colour when getting more refined)

Local mesh refinement

• By clicking the toolbarbuttons Refine mesh orCoarsen mesh andselecting the desireditems in the Draw Area

• From the Selectionexplorer by entering thedesired fineness factorvalue

• By invoking RMB contextmenu after item selection

Generate Mesh

• Can be done by clicking theGenerate mesh button from theMesh Toolbar or the right mousebutton popup menu

• While the mesh is beinggenerated, the possibilities areoffered to either pause, resumeor cancel the process

The Water Levels Mode

Water Levels

• Generated water level is created by specifying a Head in the boreholes (inthe Soil mode) and is the default water level– A single borehole can be used to create a horizontal water surface that

extends to the model boundaries.– When multiple boreholes are used, a non-horizontal water surface can be

created by combining the heads in the various boreholes– Non hydrostatic distribution in the soil may be specified in the Water

tabsheet of the Modify soil layers dialog box• User water levels are available in the Water levels mode and can be used

as a alternative to the Generated water level.

Water conditions in soil volumes• Water levels can be specified

for each individual volume• Available options are:

– Global level (default)– Custom level– Head– User-defined– Interpolate– Dry

• Can be done from– The WaterConditions feature

in the Selection explorer.– Right-clicking the mouse

The Staged Construction Mode

Calculation phase definition

Phase explorer

Change and/or (de)activate objectsper phase by means of theModel explorer, Selection exploreror directly in the Draw area

The Phase explorer

• For creating and editing the calculation phases

Add phase

Calculation status indicator

to be calculated

not to be calculated

calculation successful

calculation failed

Calculation type indicator

K K0 procedure (initial phase)

G gravity loading (initial phase)

P plastic

D plastic drained

C consolidation

S safety

Insert phase Delete phase Define phase settings

Defining Phase settings

• Calculation phase settings can beedited:– Calculation type– Phase parameters– Iterative procedure settings

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