To determine the maximum allowable slope for an excavation you need to know the soil type in the area. Remember that ALL of these sloped excavations have a maximum depth of 20 FEET, any deeper than that and you must use some form of shoring or layering.
|Soil Type||Max Allowable Slope (H:V)|
|Type A||3/4 : 1|
|Type B||1 : 1|
|Type C||1 1/2 : 1|
accordng to OSHA the slope can never exceed 1 : 2.
Solid mineral material that remains upright, stable, and intact when it is excavated.
Type A (compressive strength or greater)
These are cohesive soils that contain a good amount of clay. A soil cannot be Type A if:
1. it has cracks
2. there is vibration from traffic or some other source nearby (factory)
3. It has been disturbed recently (geologically recently, like a hundred years)
4. soil is part of a sloped + layered system Click here to continue reading