D-Pile GrouP

3D modelling of single piles and pile groups

In 1988, Deltares (formerly known as GeoDelft)

started a research project on the behaviour of

mooring dolphins. Deltares was asked to do so by

the Dutch Ministry of Public Works. Within the

project, it was shown that many different methods

exist to perform calculations on single horizontally

loaded piles and pile groups. Each method has

its own advantages, but also limitations. None of

the individual methods met all the criteria of the

Dutch Ministry of Public Works. Therefore, Deltares

decided to build a computer program that would

hold several of these calculation models. The great

advantage would be that the user could switch from

one model to another, using the same input when

applicable. One of the extra criteria for this program

was that calculation times should still allow for

practical use. The resulting program D-Pile GrouP

has proved to be very useful. Previous releases of

D-Pile GrouP were called MPile. For the modelling

of pile groups two issues are important. First of

all the behaviour of individual pile(s) in their own

ground profile is taken into account. Secondly one

has to account for the behaviour (interaction) that

each pile imposes on all other piles through the

soil and through a superstructure. These issues are

addressed in D-Pile GrouP using different models

that range from a standard model to more complex

models.

General

D-Pile GrouP enables the analysis of the three-dimensional

behaviour of single piles and pile groups, interacting via the pile

cap and the soil, as a function of loading. For this purpose D-Pile

GrouP offers a unique combination of the internationally accepted

design rules of the API (American Petroleum Institute) and special

soil interaction models all within the same graphical user interface.

One of the great benefits of D-Pile GrouP is that switching between

different computational models is very easy since all relevant input

data of the previous model is kept. This flexibility gives the user the

opportunity to choose between a fast and simple calculation and

a more complex but more accurate calculation, in a way that best

suits particular needs. The choice of models to be used depends

principally on the distance between piles. Some specific features

of D-Pile GrouP are:

Piles

• Analysis of all pile types, both pre-defined standard or

userdefined special piles.

• Pile sections with different properties.

• Options for inclined piles (Cap; Cap Soil Interaction module and

Dynamic module).

• Pile head fixed or hinged clamp in the pile cap (freely rotating).

Soil resistance

• Automated spring generation according to the API for sand

and clay layers, for static or cyclic loading, with common input

properties.

• Influence of the pile tip resistance (elastic or elasto-plastic).

Loading

• Load on the cap by moments, horizontal and vertical forces,

rotations and displacements.

• Load by horizontal and vertical soil displacements (Cap module).

• Effect of surcharge (Cap interaction module).

• Monotonous increasing loads, load reversal and repeated (cyclic)

loads.

• Dynamic load by ship collision (Dynamic module), a model for

undrained behaviour of sand.

• Multiple models for the interaction between piles via the soil.

Output facilities

• Graphical output of displacements, shear forces and moments

in top view.

• Graphs of cap displacements and rotations versus loading.

• Graphs of internal forces and soil reactions along the piles.

• Automatic generation of a calculation report with tables and

graphs in rich text format. Exporting plotted data (e.g. to Excel).

D-Pile GrouP3D modelling of single piles and pile groups

Pile properties window

D-Pile GrouP comes as a standard module, which can be extended

further with other modules to fit more advanced applications:

• D-Pile GrouP Standard module (Poulos model)

• Cap module (included in Standard module)

• Plasti-Poulos module

• Cap Soil Interaction module

• Cap Layered Soil Interaction module

• Dynamic module.

Standard module (Poulos module)

The standard module is intended for the analyses of single piles

and/or pile groups, using the Poulos module or the Cap module. The

Graphic User Interface allows for the input of projects, running the

analyses and provides tabular and graphical output of results both

on screen and in a report. The program provides ample options for

recalculation, using different pile types and fine-tuning of the pile

plan. In this manner a cost efficient design can easily be obtained.

Some specific features of the standard module will be described in

the following paragraphs:

Pile grid generator

The pile grid generator eases the input of complex pile plans for

equally spaced as well as non structured pile groups. After the input

of piles it is possible to check each pile graphically.

Loads and soil displacement

Loads and moments can be applied on the superstructure in all

directions (x, y and z). As an alternative to force and moment

controlled loading any of the loads can be replaced by its

corresponding displacement or rotation. It is thus also possible to

apply a prescribed translation or rotation in some or all directions

(x, y and z). In the Cap module the piles can also be loaded directly

by soil displacements.

Output

Input and output tables, graphs and a report are available for

printing, viewing and for export to standard Windows applications

through the Windows clipboard. Charts are available to show

displacements, bending moments, shear forces, in x, y and z

direction for individual piles. It is also possible to view results for

Raking piles in High Speed rail viaduct

Pile grid generator

Pile properties window

displacements, bending moments and shear forces in a top view for

all piles. Cap displacements and rotations can also be visualised.

Poulos model

The Poulos model is an analytical model that takes into account

elastic soil behaviour for two soil layers. One layer along the

pile and one layer located below the pile tip. Cap interaction and

interaction between piles is taken into account. The Poulos model

is especially useful in a first analysis, when only little data is

available or when the loads are small and the soil is expected to

behave mainly elastically.

Features

• Elastic soil behaviour.

• 2 layers.

• Pile-soil-pile interaction for 2 layers.

Cap module

The Cap module is included in the standard module of D-Pile GrouP.

The Cap module includes multilayered soils using linear or non linear

(elasto-plastic) springs. Cap interaction is taken into account, but

interactions between piles through soil are not taken into account.

The Cap module is therefore especially useful for single pile

analyses or pile groups with relatively large spacing. Generation

of the springs requires limited input and offers choices ranging

from automatically created elasto-plastic springs according to

the API rules to fully user defined spring characteristics (linear or

elastoplastic).

Features

• Elasto-plastic soil behaviour.

• Layered soil (max. 99 layers).

• No pile-soil-pile interaction.

• Input of prescribed displacements.

• Raking piles.

Plasti-Poulos module

As an extension of the Poulos model the Plasti-Poulos model

includes non linear single pile behaviour based on the analysis of a

pile in multilayered non linear soil. The behaviour of the half space

is similar to the Poulos model (elastic). The Plasti-Poulos model

can therefore be used for more accurate analyses compared to the

Poulos model, in particular when larger loads are imposed and the

system starts to show non linear effects.

Features

• Elasto-plastic soil behaviour.

• Layered soil (max. 99 layers).

• Pile-soil-pile interaction for 2 layers.

Poulos model

Cap model

Plasti-Poulos model

Output window for individual piles

Cap Soil Interaction module

The Cap Soil Interaction module includes single pile behaviour

based on the behaviour of multilayered non linear soils by means

of lateral and axial (elastic/elasto-plastic) springs. It allows

for input of non uniform piles while elastic soil-pile-soil group

interaction is taken into account. This module is advised for small

group spacings. It is not as fast as the above mentioned models,

but provides detailed data about forces and moments along the

length of the piles. It also allows for the use of surface loads.

Features

• Elasto-plastic soil behaviour.

• Layered soil (max. 99 layers).

• Pile-soil-pile interaction for 1 layer.

• Surface loads.

• Raking piles.

Cap Layered Soil Interaction module

The Cap Layered Soil Interaction module is our most sophisticated

model and includes single pile behaviour based on the behaviour

of multilayered non linear soil modelled in continuum finite

elements. It allows for input of non uniform piles while layered

soil-pile-soil group interaction is taken into account. This model

is also advised for small group spacing where detailed data about

forces and moments along the length of the piles is needed.

Features

• Elasto-plastic soil behaviour.

• Layered soil (max. 99 layers).

• Pile-soil-pile interaction for all layers.

• Raking piles.

Dynamic module

The Dynamic module is a dedicated calculation model for dynamic

analysis of a collision of a ship against a pile cap. It can be used

for both single-pile and multi-pile dolphins. It accounts for

the inertia effects due to the mass of the cap and the piles. The

loading is restricted to a mass (ship) impacting the cap at a point,

in a direction and at a speed which can be selected by the user. It

also incorporates a special soil reaction model that accounts for

undrained lateral loading in sand.

Features

• Layered soil (max. 99 layers).

• No pile-soil-pile interaction.

• Raking piles.

Support

Deltares systems tools are supported by Deltares. A group of

70 people in software development ensures continuous research

and development. Support is provided by the developers and if

necessary by the appropriate Deltares experts. These experts can

provide consultancy backup as well.

On-line software (VMware)

All popular geotechnical Deltares simulation products are available

over the internet via our Online Software service (Software as

a Service (SaaS)). An internet connection and subscription is

sufficient for worldwide access. Billing is according to the actual

use and subscription costs per quarter.

Cap Soil Interaction Model

Cap Layered Soil Interaction model

Time-force curve after ship collision

PO Box 1772600 MH DelftBoussinesqweg 12629 HV DelftThe Netherlands

T +31 (0)88 335 81 88software@deltares.nlwww.deltares.nl/softwareonlinesoftware.deltares.nl

Time-force curve after ship collision

Photo’s by: Elsam A/S and BeeldbankVenW.nl, Rijkswaterstaat.