Temporary slope stability - Excavation
Temporary slope stability - Excavation
(OP)
I've been set the task of designing a temporary batter behind a subway wall. It's got to withstand the standard highway loads. there is limited working space due to where the carriageway is and so I've suggested a 2:1 slope for about 2m from the subway wall then tappering down to 1:1. The soil is very stiff clay (cannot be indented with thumb). How can I check the stability of the slope. Would I use the standard formular for active pressure (Pa = Ka.gamma.h - 2Cu) and just assume a value for Cu? or is there another method of annalysis?





RE: Temporary slope stability - Excavation
How tall is the cut? If the cut is very small, appoximately less than 10 feet (3 meters) the geotechnical engineer might be able to say it is stable based on experience.
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
Eric pointed out something of interest - seams of sand and silt - or pockets even. Definitely important as is any fissures with the stiff clay. I'm surprised you are thinking hand shear vanes in a stiff clay that you can't indent with a thumb. Inconsistant.
As has been mentioned, there are computer programmes and the like; but, if you want to get a feel, pick up a Terzaghi and Peck (1967 version is better I think) and look in the book for Taylor's charts. This, and formulations for getting Stability numbers - and relating it to other properties will give you a handle on what the FS is. Of course, you need to think about water filled tension cracks, etc.
Cheers - but get a geotech to help you.
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
From strictly a liability perspective, GET THEE TO A GEOTECH! Of course, if you want to take the risk of killing somebody, I'm sure that your boss and client will understand...NOT!
Jeff
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
RE: Temporary slope stability - Excavation
I have spent years and many classes studying soils and slopes in particular. To think that anyone can just purchase a program and suddenly become an expert able to analyize slope stability is incredible. There are many, many things that need to be taken into consideration (much have been already listed by other posters) ESPECIALLY in clay slopes!!
As has been said by everyone already... hire an experienced geotechnical engineer or don't do it.