Seismic Design of Cantilevered Soldier Pile Walls

[Jenoside]

Does anyone have a reference for how to design cantilever (i.e. not anchored) soldier pile walls for seismic loading. I am using the Mononobe-Okabe Method as specified in the 17th Edition of AASHTO.

Thanks.

 

[FixedEarth]

Use equation 2 of the attached PDF. Kh is taken as one third of PGA and is between 0.1 to 0.2g. H is your excavation shoring height.

You could either use the inverted triangle as a distributed load and add it to your earth pressure or use it as a line load (get the area) and apply it at 0.6H above the subgrade level.

They are directly from the lateral Stress Conference Paper of 1971 by Seed and Whitman.

 

[Geostructsparks]

According to AASHTO 17th Edition Kh is 1/2 of the peak ground acceleration, unless you are designing an anchored wall (not your design) which required 1-1/2 times peak ground acceleration. If you are in a high seismic area it should not be limited to 0.2 g. However, you can also use the displacement-based design per AASHTO to reduce your kh slightly if you can permit the movement.

Current design agrees that you need to also include the horizontal seismic inertia of the wall itself and any soil wedge considered behind the wall. The weights of both should be multiplied by the peak ground acceleration, or Kh (1/2 the peak ground acceleration). Other than that and you can use lower factors of safety, its basically the same steps after that point as conventional wall design (determine all your forces, moments, design the sections)

 

[InDepth]

Is the cantilever wall permanent or temporary? If the wall is temporary you can reduce the seismic forces based on probabilistic methods (seismic return period). You can use ASCE 41 equations.

If it is permanent, you have to decide wether to design the wall for 10% in 50 yr event or a 2% in 50 yr event. Also, you must decide wether you want the shoring wall to be life safe or if you want it to be operational (serviceability / deflection controlled).

Now, the other assumption you can use to reduce the seismic forces is to assume a certain plastic yield factor (structure or soil) to reduce your effective seismic forces.

Just a tickler for your thoughts.