Wick Drains

1.0 Introduction

This tutorial introduces the Wick Drains feature in RS3. Wick drains allow water to dissipate faster when placed in the soil before excavation to speed up the process of consolidation. In the tutorial, we cover how wick drains are used in the staging of an embankment construction along with traffic loading at the end. The results show the change in the pore pressure and total head due to the application of the wick drains, which is shown in this tutorial.

2.0 Model

To start the tutorial, open the Embankment Consolidation–no wick drain-final file. Because this tutorial focuses on applying wick drains, we will start with a completed model.

2.1 PROJECT SETTINGS

We’ll start by checking that the model’s Groundwater and Stages Project Settings are set up as needed.

Select Analysis > Project Settings.
Select the Groundwater tab to view Method = Transient settings.
Select the Stages tab to view how the staging is set up.

2.2 MODEL DESCRIPTION

All the embankment pieces have no materials assigned in Stage one, and the material was changed to Embankment Fill from the bottom to top for Stage 2 to Stage 5. You can check this by toggling across the Stages tabs along the bottom of the model image.

For instance, Stage 1 has no embankments installed, as shown below:

Image of Stage 1 having no embankments installed

Stage 5 has all the embankments installed, as shown below:

Image of Stage 5 has all the embakments installed.

At Stage 5, a load of 10 kPa has been applied to the surface of the. You can check this by going to the Loads workflow tab and selecting the load on the Visibility Tree at Stage 5.

Image of Stage 5

The following Boundary Conditions of -10.5 m of pressure head have been defined on the face of the embankment. You can see this by selecting the Groundwater workflow tab.

Screenshot of Boundary Conditions after selecting Groundwater workflow tab

Additional steps in creating the model are:

Defined the refine region for mesh using the box that we have with the size of 1.5.
Meshed with uniform size 2.
Defined the restraints, fix x,y on the side and x,y,z on the bottom.

Image of additional steps

3.0 Compute

Compute the Solid by selecting the Compute workflow tab and then selecting Compute (Groundwater Only) on the toolbar .

4.0 Results

Select the Results workflow tab.
Select the Legend in the contour plot option on the right side of the screen and change the data type to Seepage > Total head.
Similarly, change the data type to Seepage > Pore Pressure and you will see the results shown below:

Now we will focus on applying wick drains.

5.0 Embankment With Wick Drain

Hide the embankment pieces in order to apply the wick drains under embankments before applying the embankments.
Select the following embankments and select visibility off.
Selection face mode ON and select the faces below the embankment.
Go to Groundwater->Add wick drain. Polyline dialog will pop up.
Under the Plane Options coordinate in x, y, z, Change the Z value in the Origin to -5 (0,00, 0,00, -5) as also shown below.
Draw a polyline around the orange surface in the above figure and select the green checkbox.
Enter the following information in the wick drain dialog.

Spacing: X = 4, Y = 4
Grid Origin: X = 52.248, Y = 26.892, Length = 20
Wick Drain/Relief Well Properties: Type = Wick Drain, Pressure Type = Pressure, Pressue = 0, Diameter = 0.1
Install at Stage 6 and Remove at Stage 11

Wick Drain Dialog

5.1 COMPUTE

Compute the model by selecting the Compute workflow tab and then selecting Compute (Groundwater Only) on the toolbar .

The model is highly non-linear so it is expected to be slow in computation. The program needs to iterate to get to the right stage. Note that the principle of the wick drain is similar to unknown boundary conditions where the pore pressure inside the wick cannot be larger than the pressure, however, smaller is fine. The computation for this model will take approximately one hour to compute.