Seismic Lateral Earth Pressure for Retaining Wall Design
Seismic Lateral Earth Pressure for Retaining Wall Design
(OP)
I am designing a retaining wall but I cannot seem to find a straight answer on how to calculate the Kh factor. I have read about it on different sources and they all seem to say something different. This is what I have seen:
Kh = Sds/2.5 Kh = 0.5*PGA Kh = PGA Kh usually ranges from 0.5 to 0.3
Any thoughts. The project is in California, so there is high seismic activity.
Thank you
Any thoughts. The project is in California, so there is high seismic activity.
Thank you






RE: Seismic Lateral Earth Pressure for Retaining Wall Design
1) My tendency is to lean towards the Sds/2.5.
2) Retaining walls that are designed well for regular loading seem to have performed pretty well in earthquakes in the past.... Despite the fact that very few of them were designed for seismic loading.
I'm glad the code is trying to define this concept better in recent cycles. Because there are projects where the retaining walls are pretty critical. That being said, for those projects (where liquifaction might be an issue or the entire site stability is based on a tall retaining wall) my tendency would be to let the geotech handle the wall.
For the more boring conventional retaining walls that I've designed, my tendency is to believe that seismic design of these walls isn't truly necessary.
RE: Seismic Lateral Earth Pressure for Retaining Wall Design
RE: Seismic Lateral Earth Pressure for Retaining Wall Design
RE: Seismic Lateral Earth Pressure for Retaining Wall Design
And, the fundamental question is what Kh to use as the basis for the M-O pressures? That's where the consensus seems to be lacking....
RE: Seismic Lateral Earth Pressure for Retaining Wall Design
Chapter 8 of Braja Das's 'Principle of Soil Dynamics' is devoted to this subject. If you look at just about all the comparisons they cite (between experimental and theoretical values) they are all off by a pretty significant factor. Fortunately, they have comparisons between some of those values in charts.
Further complicating the matter is the fact the magnitude and distribution of the pressures on the wall depend on how the wall itself yields (i.e. rotation about the bottom, translation, or rotation about the top; Das addresses all 3 in the reference). You combine that with a large number of possible experimental input parameters (i.e. frequency input motion, etc) and you see why there isn't a consensus.
That's why I suggested a few posts back to rely (if possible) on a Geotech's opinion (like we do so many other times). You can always fall back on that (if something goes wrong)......and back check it yourself to see if it makes sense.
RE: Seismic Lateral Earth Pressure for Retaining Wall Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.