Article

New Pile Supports in RS2

New Pile Supports in RS2

by Daniel Wai

RS2 has improved the ability to model piles using the new dedicated Pile Support Type. Pile supports have a beam component for capturing the structural behaviour as well as an interface component to capture the soil-pile interaction behaviour, namely the skin and end bearing resistance. The new pile support formulation offers improved modelling of soil flow around a pile.

Before this feature was developed, pile behaviour was best captured using structural interfaces which, as the name suggests, also have structural and interface components. Pile properties would need to be converted to equivalent structural interface properties per unit out-of-plane. As shown in Figure 1, with the new dedicated pile support type, the user simply enters the pile properties and out-of-plane spacing. RS2 will take care of the rest. Furthermore, the user can define the pile-to-raft connection type (i.e. free, hinged, rigid, and semi-rigid) which are automatically applied when a pile intersects a liner. The user enters interface properties to define the skin and end bearing resistance. Various skin resistance models are available including Elastic, Mohr-Coulomb, Linear, Multi-linear and Material Dependent.

Figure 1: Define Pile Properties dialog (Interface)
Figure 1: Define Pile Properties dialog (Interface)

The beam component is defined using the familiar liner properties. The user has the choice of a constant liner property throughout the pile or to define beam segments by length. As shown in Figure 2, the Define Beam segment by length option allows different beam properties along the pile when the design requires multiple sections. As shown in Figure 3, the user can also add forces or displacements on the top or bottom of the pile which can be staged. This can be used for modelling the construction process or pile load tests.

Figure 2: Define Pile Properties dialog (Beam - Define Beam Segment by Length)
Figure 2: Define Pile Properties dialog (Beam - Define Beam Segment by Length)
Figure 3: Define Pile Properties dialog (Force/Displacement and Stage Factors)
Figure 3: Define Pile Properties dialog (Force/Displacement and Stage Factors)


Example: Piled Raft Foundation Design

Figure 4 presents a piled raft foundation design. A uniform distributed load of 30 kN/m2 was applied to the piled raft built on a single clay layer. A firm rock layer is located directly under the clay, 40 m from the ground surface. A groundwater table is located 3 m below the ground surface. The 20 m long square pre-cast concrete piles are 275 mm in width and are installed with a 16 x 16 m2 raft. The piles are evenly spaced at 4 m. A Mohr-Coulomb skin resistance model is assumed for the interface behaviour. As shown in Figure 5, the pile properties can be directly entered into the new Define Pile Property dialog. Figure 6 presents the RS2 total displacement contours with pile axial force overlaid to show the performance of the pile raft foundation design. Full details on how to create the model can be found in our Piled Raft Foundation tutorial.

Figure 4: Piled Raft Foundation Example Layout
Figure 4: Piled Raft Foundation Example Layout
Figure 5: Piled Raft Foundation Example - Define Pile Properties dialog (Interface)
Figure 5: Piled Raft Foundation Example - Define Pile Properties dialog (Interface)
Figure 6: Piled Raft Foundation Example – RS2 model – Total Displacement Contours with Pile Axial Force Overlaid
Figure 6: Piled Raft Foundation Example – RS2 model – Total Displacement Contours with Pile Axial Force Overlaid


We can further improve the model by repeating the analysis in RS3 which can better capture 3D effects. Figure 7 presents the total displacement contours for the piled raft foundation design modelled in RS3 that shows similar deformations.

Figure 7: Piled Raft Foundation Example – RS3 Model
Figure 7: Piled Raft Foundation Example – RS3 Model

How to get this update

If you’re an existing customer and have a Maintenance+ subscription, check your inbox now for an email from us with download links and instructions for updating your license.

If you’re a license owner but don’t have Maintenance+, now’s your chance to subscribe to our enhanced maintenance and support service. Maintenance+ gives you the peace of mind of knowing that you’re always working with the latest version of your software. To subscribe now, contact us at maintenanceplus@rocscience.com.

Finally, if you’re a new customer, give RS2 a try by signing up for a free trial version.

Back to top

More from Rocscience