# shaft.nordlund_k_delta()

Nordlund lateral coefficient for a non-tapered displacement pile.

Usage

[Source](https://github.com/lornearnold/driven-pile/blob/main/src/driven_pile/shaft.py#L21-L48)

``` python
shaft.nordlund_k_delta(
    phi,
    displaced_volume,
)
```

## Parameters

`phi: array_like`  
Friction angle, deg.

`displaced_volume: float`  
Soil volume displaced per unit length, m^3/m.

## Returns

`ndarray`  
K_delta, interpolated in log10 of the displaced volume and log-linearly in friction angle; the 35 to 40 deg slope is continued above 40 deg.

## References

Nordlund (1963, 1979) as tabulated in FHWA GEC-12 (Hannigan et al., 2016).