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GGU-RETAIN: Analysis of vertical capacity

Detailed notes on this analysis concept are included in EAU 2012, Section 8.2.5.5, and in the Recommendations on Piling (2012).

The analysis is activated in the "Editor 1/Verifications/Partial factors" menu item using the "Perform 'Vertical capacity' analysis (EAU, EAP and EAB)" check box. In accordance with EAB R 84, it demonstrates that the design action V,d does not exceed the design resistance R,d from end resistance and skin friction: µ = V,d / R,d ≤ 1. The results are shown in the "Sum V FOS summary" menu item.

Skin friction

Skin friction is only adopted below the excavation base.

  • "Method 1: EAU Figure R 4-3 (left)": Above the theoretical toe point (TF), the vertical component of the passive earth pressure is used as resistance. With "Use the EAU 2022 annual report", no skin friction is adopted there.
  • "Method 2: EAU Figure R 4-3 (right)": Skin friction is adopted from the excavation base.

For sheet pile walls with empirical data to "EAB 2021", the "Wall is excavated" check box activated and Method 2, skin friction between excavation base and TF is doubled in accordance with EAB R 85, paragraph 4 a). From version 13.6 onwards, own empirical data are not doubled; they are used as you enter them.

Extension and minimum embedment

  • "Extension below TF [m]:" extends the wall for this analysis only. The extension is measured from the bottom of the section, not from the TF. It increases skin friction and self-weight; the end resistance is determined at the lower toe point.
  • "Minimum value" [m] ("Minimum embedment in load-bearing strata" group): If the toe point is embedded less deeply in load-bearing strata, the analysis is considered not demonstrated. EAU and EAB do not require a minimum embedment; a value of 0.0 switches the check off.

Empirical data

For each soil you enter either qc (non-cohesive soil) or cu,k (cohesive soil) in "Editor 1/Soils". From these, the program determines qb,k and qs,k using the selected empirical data (EAU, Recommendations on Piling or EAB 2021). A soil with qc = 0 and cu,k = 0 is considered not load-bearing: it provides neither skin friction nor end resistance. New soils are preset with qc = 10 MN/m² and cu,k = 0; if you do not change these values, the program uses qc = 10 MN/m².

With "Use own empirical data" you instead enter qb,k [MN/m²] and qs,k [kN/m²] for each soil in "Editor 1/Soils". qs,k is used as entered. qb,k is only used unchanged if "Calculate qbk by averaging qc or cu,k" is deactivated; otherwise the value is converted like qc using the tables.

Partial factors and reductions

End resistance and skin friction are divided by "gamma(qb,k)" and "gamma(qs,k)" respectively and multiplied by "End resistance reduction" and "Skin friction reduction" respectively. With "Consider adjustment factor eta(t) compliant with EAB R 85", the end resistance is reduced for small embedment depths in accordance with EAB R 85, paragraph 7; with empirical data to the Recommendations on Piling, their adjustment factors are applied in addition. A group effect of closely spaced elements is not considered.