> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/technical-background/soil-structure-interaction/axial-soil-models/axial-qz-soil-models/driven-pile-clay-qz-api-api-2007.md).

# Driven Pile Clay QZ (API) \[API, 2014]

API RP 2GEO gives the unit end bearing of piles in cohesive soils in Section 8.1.3 and the tip load-displacement curve in Section 8.4.3. Both provisions are those of API RP 2A-WSD \[API, 2007], Sections 6.4.2 and 6.7.3. The only input is the **Undrained Shear Strength** at the pile tip.

$$
\tag{1}
q = 9s\_u
$$

where $$q$$ is the unit end bearing and $$s\_u$$ the undrained shear strength of the soil at the pile tip (written $$c$$ in RP 2A-WSD).

The recommended curve for both sands and clays is:

| $$z/D$$    | 0.002 | 0.013 | 0.042 | 0.073 | 0.100 |
| ---------- | ----- | ----- | ----- | ----- | ----- |
| $$Q/Q\_p$$ | 0.25  | 0.50  | 0.75  | 0.90  | 1.00  |

where $$z$$ is the axial tip displacement, $$D$$ the pile diameter, $$Q$$ the mobilized end bearing and $$Q\_p$$ the total end bearing, $$q$$ times the gross tip area of the pile. The standard has no displacement input for this curve.

***

\[API, 2014] American Petroleum Institute (2014). *Geotechnical and Foundation Design Considerations*, API RP 2GEO, 1st ed. (2011) with Addendum 1 (2014), reaffirmed 2021, Sections 8.1.3 and 8.4.3.

\[API, 2007] American Petroleum Institute (2007). *Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms — Working Stress Design*, API RP 2A-WSD, 21st ed. with errata and supplements, Sections 6.4.2 and 6.7.3.


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