GGU-RETAIN: Worked example 2: Sheet pile wall with corrosion

Initial system

Several years ago, a 10.25 m long sheet pile wall (AU 23; S 240 GP) was installed in a harbour. At the top of the sheet pile wall a very steep, 0.30 m thick armour was subsequently constructed. The gradient is 1:1.30. The armour is stable if a horizontal load of 10.7 kN/m and a vertical load of 5.0 kN/m can be accepted at the top of the sheet pile wall.

A residential building was erected together with the armour at the rear of the sheet pile wall, built on a pile foundation to avoid additional loading on the sheet pile wall.

Figure 3 Illustration of worked example 2

This example is included in the file "Manual example 2-1.vrb" in the program's Examples folder. Once you have opened the file you can follow the input described in the previous example in the relevant menu items in "Editor 1" and "Editor 2".

The sheet pile wall is analysed as elastically bedded (menu item "Editor 2/Subgrade reaction moduli").

To avoid unrealistically high differential water pressures the subsurface hydraulics are investigated using flow conduits (menu item "Editor 1/Groundwater").

The new system can be verified using the specifications described above.

System with corrosion

However, an additional 4 mm of corrosion on the water side must be investigated. In "Editor 2/Sections" there is a "Simulate corrosion" button opening the following dialog box:

After selecting the section and entering the corrosion, new section data are calculated, and a new section name proposed.

EAU 2012 8.1.8.4 stipulates that analysis may be based on DS-A.

Analysis still fails using the newly calculated section data (see file "Manual example 2-2.vrb").

System with partial corrosion

The section is not corroded along its whole length, only in the low-water zone.

A second analysis using several steel sections is performed.

Once the "Using several steel sections or inserted beams" check box is activated the following system can be investigated ("Editor 2/Section data"):

4 mm of corrosion are assumed down to 3 m. Below this the section remains undamaged.

Using these specifications analysis is successful (file "Manual example 2-3.vrb").