Slope Stability - Open cut excavation

[Zambo]

I have a foundation about 3m deep which I want to excavate open cut. I have space available around the excavation so do not need to add the expense of an earth support system. But how to calculate a safe angle for the stability of the excavated face. The excavation is in sand and I plan to use tarpaulin covers to give some erosion protection during the construction of the foundation.

 

[dgillette]

A couple of cheap ways to fly:

http://www.osha.gov/dts/osta/otm/otm_v/otm_v_2.html

http://www.safety.duke.edu/ohs/Documents/ig14.pdf

I don't know what country you are in, but following US OSHA standards would probably keep you out of trouble, as long as you don't have anything weird at your site. Make sure you account for water table if it's within your 3 m depth.

Cheers!
DRG

 

[cvg]

to reduce your liability -

[ul]
[li]if you are going to follow minimum OSHA standards, then let the contractor specify the temporary cut slopes and let them design any necessary shoring.[/li]
[li]if you (a registered engineer) are recommending temp cut slopes or shoring, then you need to follow the standard of care, which generally means you are a qualified geotechnical engineer[/li]
[/ul]

 

[chicopee]

Read your OSHA excavation standard carefully as you could encounter different soil layers. A ratio of three (3) horizontal to one (1) vertical bears to mind for sand.

 

[cvg]

this is a type C soil according to OSHA 1926 Subpart P. maximum allowable slopes for excavations less than 20 feet deep are 1.5H:1V (34 degrees). slope length may be reduced by shoring or benching. slope angle may be decrease if their is groundwater or signs of slope distress. contractor's competent person should be the one making this call. alternatively, a qualified registered engineer can design slopes based on actual soil data.