Lateral RW pressures for UDL & Point loads

[Gavin73]

Hi I am looking at some formulas which give lateral pressure distributions on retaining walls for point & UDL surcharge loads. The formulas do not reference Ka or K0 (AS4678 figure J7) or suggest how to modify these pressures for different Ka / K0 values. Does anyone know where I can find formulas for the above which incorporate Ka / K0? Thanks

 

[dcarr82775]

The Boussinesq equations for pressure distribution. I am not familiar with the document you reference, but Boussinesq is the only method I have come across for distribution of point loads. This method assumes the wall itself is unyielding which is why it doesn't reference soil parameters. I use my own judgement in how to 'reduce' those loads to account for wall movement

 

[UncivilEngineer]

For uniformly distributed surcharge loads you could use a Rankine approach using either Ka or Kp.

For example, p = q x Ka

 

[UncivilEngineer]

I meant Ko (not Kp). Ko would be appropriate for non-yielding walls under this approach.

How do you edit posts here?

 

[msquared48]

UncivilEngineer:

Prior to posting.

Mike McCann, PE, SE (WA)

 

[CWEngineer]

EM 1110-2-2504 Desing of Sheet Pile Walls provides formulas for vertical variation of pressure behind a wall for a point load.

 

[RFreund]

CWE -> These are the elastic methods noted by dcarr. These are popular but there are others. I hope to make a collection some day.

One that gets overlook, surprisingly, is made by Terzaghi (thanks to FixedEarth to point this out to me) pg 367 of Soil Mechanics in Engineering Practice

Basically he establishes a 'C' factor and states that the load travels at a 40 deg angle relative to the horizontal and is applied where that line hits the wall.
'C' is the ratio of vertical to horizontal force

1. Course-grained without fines (clean sand and gravel) = 0.27
2. Course-grained w/fines = 0.3
3. Residual soil w/stones, fine silty sand or granular materials w/ conspicuous clay content = 0.39
4. Very soft or soft clay, organic silts, silty clay = 1.0
5. Medium or Stiff clay = 1.0

The last one seems odd, as in too conservative, but what do I know. I'm not Terzaghi.

EIT

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