Retaining Wall Slip
Retaining Wall Slip
(OP)
Question: I designed a concrete retaining wall, the base is 500mm thick. Now my design usually allows for a safety factor of 1.5 against slip/sliding. In this design a very small force is used as passive pressure onto the front toe of the 500 thick wall base.
If the base is excavated into virgin ground, (dense solid gravelly material), for the base to slide this 500 thick base must push through this material. So in reality the reactive force on the toe of the wall from the in situ soil material is much higher than the passive force used in the sliding calculation, as long as it is okay for the wall to move slightly so that this soil can compress provide a reaction force.
Sure there might be some movement as the toe pushes into the soil but as it then compresses how will the wall slide, it must shear through this material, am I right?
Has anyone ever seen or heard of a retaining wall slide before actually overturning or failing in bending of wall?
Just seems to me that in the described case the calc for sliding is too conservative in most cases.
If the base is excavated into virgin ground, (dense solid gravelly material), for the base to slide this 500 thick base must push through this material. So in reality the reactive force on the toe of the wall from the in situ soil material is much higher than the passive force used in the sliding calculation, as long as it is okay for the wall to move slightly so that this soil can compress provide a reaction force.
Sure there might be some movement as the toe pushes into the soil but as it then compresses how will the wall slide, it must shear through this material, am I right?
Has anyone ever seen or heard of a retaining wall slide before actually overturning or failing in bending of wall?
Just seems to me that in the described case the calc for sliding is too conservative in most cases.






RE: Retaining Wall Slip
http://www.nceng.com.au/
"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."
RE: Retaining Wall Slip
I don't recall ever seeing a sliding failure, but I have seen several overturning failures. If you want to complain about the 1.5 factor on sliding, etc. join the club many a discussion can be found on this board.
RE: Retaining Wall Slip
on shorter walls, the top of the stem wall may not deflect enough to put you in the Active state. So now your actual backfill earth pressure coefficent is somewhere between Ka and Ko. So in the long term, the 1.5 safety factor is actually a minimum value needed for stability given all the variations that take place in soils.
http://www.soilstructure.com/
RE: Retaining Wall Slip
once it starts sliding, wouldn't the soil now be in active state so it is self limiting?
RE: Retaining Wall Slip
But he might of been overly conservative, and I don't think we ever had a 500mm(20") thick footing, in fact that's almost double what we normally saw in the examples.
RE: Retaining Wall Slip
http://www.soilstructure.com/