Terracing is your best bet (other than importing fill to create a more gentle slope) but be careful of the retaining walls for the terraces. If the walls fail it will be uglier and even less desirable than the present slope.
Shelby tubes are best suited for soft cohesive soils (they tend to crumple in stiffer soils). Perhaps in-situ tests may be more appropriate to your needs.......i.e. vane shear, pressure meter, dynamic cone penetrometer, etc. - good luck<br>
