Working in the Geometry Modesof Plaxis 3DRichard Witasse

Plaxis bv

Introduction• The Geometry modes of Plaxis 3D comprises the Soil mode and the

Structures mode• They are meant to fully define the model geometry in terms of:

– Soil stratigraphy– Structural elements– Soil structure interfaces– Loads– Boundary conditions

• The Geometry modes are indicated using blue tabsheets and precede theCalculation modes (green tabsheets) when building up a model fromscratch

The Soil Mode

Introduction to the Soil Mode

• Meant to define soilvolumes and initial waterlevels

• Based on the concept ofboreholes like in Plaxis 3DFoundation

• Offers import geometryfacilities

• Adjust Soil Contour

Create Borehole

Import Soil …

Show Materials

Soil Mode Toolbar

Adjust Soil Contour• The model contour can be adjusted by

Moving an existing points or lines

Inserting a control points

Deleting an existing points

Boreholes• Boreholes are locations in the draw

area at which the information on theheight of the constitutive soil layersand location of the water table isgiven

• If multiple boreholes are defined,PLAXIS 3D will automaticallyinterpolate between boreholes andderive the corresponding positionand height of the soil layers from theavailable borehole information.

• Each defined soil layer is usedthroughout the whole model contour

Borehole 1

Borehole 2

Borehole 4

Borehole 3

Creating Boreholes

Defining Water Conditions• Water conditions can be specified

from the Modify soil layers dialog boxin the Water tabsheet

• Available options are– Head– Hydrostatic– Interpolate– Dry– User-defined

Initial Soil Conditions

• Initial soil conditions can bespecified from the Modify soillayers dialog box in the Initialconditions tabsheet

• Values specified (OCR, POP, K0xand K0y) will be using duringinitial stage calculation basedon K0 procedure

Importing Top and Bottom Model Surfaces• Definition of the top and

bottom soil layer surfaces canbe achieved as a result ofsurface import operation

• Import formats include 3DS,ITS, DWG, DWF and SLT

• Feature available for VIPmembers only

Importing Soils• The geometry of the soil

can be imported frompredefined files instead ofusing the Borehole tool

• The same import formatsas for importing soilsurfaces are available(3DS, ITS, DWG, DWF andSLT)

• Feature also onlyavailable for VIP members

Material Sets• Definition of material model parameters

for constitutive soil layers andstructural elements

• Dialog box consistent among all Plaxisproducts

• Available from many places in Plaxis3D:– Present in each model– Many shortcuts from different dialog

boxes where material sets assignmentis required

• Entry point to the SoilTest facility

The Structure Mode

Introduction to Structure Mode

• Meant to define structuralelements and loading

• Structural objects arecreated directly into a 3Dspace using mouse and/orassisting tools

– holding <Shift> while moving themouse will enable movement in Zdirection only

Default Movement Limitation• Defining 3D geometry using mouse input is cumbersome considering the

fact that the location in the direction perpendicular to the draw viewcannot be precisely defined. By default:

– mouse will enable movement in theXY plane

Changing Movement Limitation Settings

• Selecting one the six sides viewof the default views gives accessto the Movement limitation dialogboxes

• The Movement limitation dialogbox can be closed by selectingthe Perspective view option of thedefault views.

• Import volume• Import surface

• Rotate

Extrude

Array

• Points

Lines

Surfaces

Structure Mode Toolbar

• Loads

Displacements

Structures

Points• Can be generated by cilcking the Create point button• The following items can be assigned to a point

– Point load– Point prescribed displacement– Fixed-end anchor

Point load

Point prescribed displacement

Fixed-end anchor

Lines• Can be generated by clicking the Create line button• The following items can be assigned to a line

– Beam– Line load– Line prescribed displacement– Node-to-node anchor– Embedded pile

Surfaces• Can be generated by clicking the Create surface buttom• 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

Mode points/lines

Insert points

Delete points

Rotate• Rotate any selection around a rotation point compared to global axis• Possibility to directly rotate the selected objects from the draw area

using Euler angles

Extrude• Lines and surfaces can be extruded to create surfaces and volumes

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

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

Array

Further Geometrical Operations

• On top of the aforementioned geometrical operations (rotate, extrude andarray), Plaxis 3D also offers– Decompose into surfaces: create outer surfaces of selected volumes

– Decompose into outlines: create outer lines (including points) of selectedsurfaces

– Intersect: Split select geometric objects along their intersection

– Combine: Merge 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

• Can be generated by clicking the Create load button or by invoking theRMB context menu on any geometric objects in the draw area

Prescribed Displacements• Can be generated by clicking the Create prescribed displacements

button or by invoking the RMB context menu on any geometric objectsin the draw area is a very similar way as for Load definition

Point prescribed displacement

Line prescribed displacement

Surface prescribed displacement

Default Boundary Conditions• Default boundary conditions are

– All displacements fixed for thebottom surface of the soilcontour

– Perpendicular displacementfixed for lateral surfaces of thesoil contour

• Default boundary conditionscan be overwritten byspecifying Prescribeddisplacement surfaces on soilcontour

Structures

Fixed-end anchor

Beam

Node-to-node anchor

Embedded pile

Plate

Geogrid

Positive interface

Negative interface

• Can be generated by clicking theStructure button

• Can also be created from the RMDcontext menu after selecting:– points (fixed-end anchor)– lines (beam, node-to-node anchor

or embedded pile)– surfaces (plate, geogrid, interfaces)

Importing Geometry• Possible to import from external sources in different formats like 3D

Studio files (*.3DS), AutoCAD native (*.DWG) and interchange (*.DXF) fileformats:

– Click to import surface

– Click to import volume

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