At-Rest, At-Rest Sloping Backfill, and At-Rest Seismic

[ocgeo]

For a recent design of a non-yielding (at-rest) wall.....

For At-Rest Earth Pressure (level).... Ko = 1 - sin(phi) ---- Jaky, 1944
For At-Rest Seismic Earth Pressure.... Koe = 2*kh (where kh = 1/2 PGA-M) ---- Wood (1973); Whitman (1991); Al Atik and Sitar (2010)
For At-Rest Earth Pressure (sloping).... Ko = (1 - sin(phi))/(1 + sin(beta)) ---- Kezdi 1972
For At-Rest Static and Seismic with sloping backfill... K and Koe = ~2*M-O (Mononobe-Okabe for active earth pressure) ---- Wood (1973); Whitman (1991); Al Atik and Sitar (2010)


This is my conclusion for at-rest pressures as the majority of studies is in regards to active pressures.


Also, Al Atik and Sitar have now re-inverted the triangle to 0.33+H above the base, back from the upside down triangle for seismic pressure resultant force.

And, they have concluded that if the static factor of safety is designed at 1.5 for active forces and the ground acceleration is < 0.4g, additional seismic design is not required.

 

[CWEngineer]

Another more recent document that discusses at-rest pressures is EM 1110-2-2502.

 

[ocgeo]

Thanks CWEngineer. As I found in my research it is difficult to find the At-Rest seismic portion (Koe not discussed in this paper). The Active is discussed in the paper and refers to the traditional Mononobe Okabe equation.

The static At-Rest earth pressure in this equation for total pressure does not seem correct as the equation is taking a linear distribution with depth (z) and not a triangular, trapezoidal, or rectangular (z^2). For instance, if you use the equation for similar cases and calculate Active pressure and At Rest pressure, with the equations presented, the At Rest result is much lower after inputting the equivalent fluid pressure (Section 3-10), and should be greater than Active.