Project specific rock shoes for large diameter RR® piles

Project specific rock shoes are needed in situations where large diameter piles are facing exceptionally high loads. For such demanding cases SSAB offers technical support and calculations to define the dimensions and structure of the rock shoes.

Typical situation when these project specific rock shoes are needed is when for example exceptionally high wall thickness or high steel grades will be utilized. In those cases the resistances of standard SSAB rock shoes may be insufficient.

The analysis method

The calculations are done as 3D FE analysis. The method follows the instructions given by Finnish Transportation Infrastructure Agency and the design guidelines given in Eurocodes.

Figure 1. 3D calculation model of rock shoe with hardened dowel

Figure 2. The stress distribution in rock shoe according to analysis

The total analysis of rock shoe includes calculations for several different situations. The situations analyzed are:

• installation phase with nominal material thicknesses
• installation phase with nominal material thicknesses, but stiffeners have initial deflection to enable more accurate buckling estimates (taking into account manufacturing tolerances and situations when stiffeners might have had contact with boulders etc. in ground)
• final phase with corrosion reduction of 1.2 mm on outer surfaces
• final phase with corrosion reduction of 2.0 mm on outer surfaces

In analysis the installation phase calculations have also eccentricity and lateral forces in addition to compression forces. These are used to model the situation during installation taking into account for example sloped bed rock.

Standard rock shoes

The resistances of standard SSAB rock shoes are shown in Table 1 below.

Table 1. Resistances of standard SSAB rock shoes

All standard SSAB rock shoes have pre-approval for use in Finnish Transport Infrastructure Agency projects.

Standard rock shoes with hardened dowel for pile sizes RR400, RR500, RR600 and RR700 have also pre-approval for use in Swedish Trafikverket projects.

More information on large diameter piles: RR and RD piles Design and installation manual www.ssab.com/infra