# spt.phi_from_n160()

Friction angle from the corrected SPT blow count.

Usage

[Source](https://github.com/lornearnold/driven-pile/blob/main/src/driven_pile/spt.py#L9-L29)

``` python
spt.phi_from_n160(
    n160,
    cap=45.0,
)
```

## Parameters

`n160: array_like`  
Overburden- and energy-corrected blow count N1,60.

`cap: float = 45.0`  
Upper limit on the friction angle, deg.

## Returns

`ndarray`  
`min(cap, 26 + 5.5 log10(N1,60 + 0.01) + 0.11 N1,60)`, deg.

## References

WSDOT Geotechnical Design Manual (2022), Table 5-1 band midpoints.