Retaining wall with heaped material 2

[dbest69er]

Hey guys, I'm currently working on designing a concrete base for a steel retaining wall. The wall will retain salt (density = 12kN/m^3, angle of friction of 30 degrees). The wall will be 6.5m high but the fill will be heaped to a maximum height of 18m. I tried designing it as if it weren't heaped but the thing keeps failing due to sliding. Is there a way to calculate Active pressure force due to a limited extent heaped material? Any resources that would help me would be greatly appreciated.

 

[ishvaaag]

Certainly there is, use the Culmann method. Follow any text that explains active push through graphic statics.

 

[bootlegend]

If I am understanding your situation correctly, I use a chart out of the Naval Facility Manual, Figure 3: Active and Passive Coefficients for Sloping Backfill. You can find this online but I have forgotten the location.

 

[dcarr82775]

Sounds like a condition where the backfill slopes up behind/above the retaining wall and then levels off. I use the trial wedge method to figure the active load for this type of retainage condition. Trial wedge is wonderfully simple.

I think boot is correct in there are also some charts in the NAVFAC design manuals, but I am not positive. They are free, just google Naval Facilities Design Manuals. I think it is Manual 7.2 or 7.3

 

[dbest69er]

Thanks for the help. This is exactly what I was looking for. The only concern I have is that the backfill is not sloping indefinitely, it has limited extent (peaks at a horizontal distance of 20m away from the wall at an angle of 30°) and according to an *old* copy of Reynold's reinforced concrete designers handbook, I need to treat this case slightly different. I've used 4 different methods(including the one mentioned here) on how to deal with the active force from a sloping backfill and every one of them fails due to sliding except for the case where I treat the section on slope above the wall between the failure plane (<α) as a triangular surcharge load. Thanks anyways guys.

 

[hokie66]

Sounds like you may have to mobilize some passive soil pressure with a key. Sliding failures are nasty.

 

[IDS]

Maybe I have misunderstood what you are saying, but if accepted analysis methods indicate that the wall is not stable then you need to modify the wall design.

Modelling a stockpile as a vertical surcharge does not include all the effects. There is also a spreading force at the base of the stockpile, which will be transferred to the wall.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/