# shaft.fs_partially_liquefied()

Unit shaft resistance through soil at pore-pressure ratio `ru`.

Usage

[Source](https://github.com/lornearnold/driven-pile/blob/main/src/driven_pile/shaft.py#L143-L166)

``` python
shaft.fs_partially_liquefied(
    fs_unliq,
    ru,
    sr,
    alpha,
)
```

## Parameters

`fs_unliq: float`  
Unliquefied unit shaft resistance, ksf.

`ru: float`  
Pore-pressure ratio.

`sr: float`  
Residual strength of the liquefied soil, ksf.

`alpha: float`  
Interface factor on `sr`.

## Returns

`float`  
`max((1 - ru) fs_unliq, ru alpha sr)`.

## References

Boulanger and Brandenberg (2004).