Seismic design of Retaining walls 3

[duafar]

I would like to know what is the type of coeficient (active or seismic-Mononobe-Okabe)that we must use to affect surchrages when we design a wall for the seismic combination.

 

[cap4000]

For the Earthquake Analysis Portion use K'ae from the widely used M-O formula. You must combine the Static Lateral Load with the increment generated by the Earthquake Load for the Total Design Load. Also, obtain the "Design of Earth Retaining Structures for Dynamic Loads" Article by Seed and Whitman published in 1970. To briefly summarize it, with a Soil Internal Friction Angle of 35 degrees and the Horizontal Ground Acceleration (max) Kh=0.17, there should not be any major design penalty to pay. The safety factor still would be around 1.15 against any significant displacements. What is your Wall Dim's and the Seismic Zone you are in?? Good Luck.

 

[jbeitia]

Hi friends, I was trying to understand the Mononobe-Okabe formula to obtain the Kae coefficient when we have a slope backfill in a retaining wall. For example, if the internal friction angle is 33degrees and the slope is 33degrees, there is an error in the formula. Can somebody tell me what to do on this case?

 

[rockchip]

jbeitia - the reason the formula "blows up" is that you are analyzing a marginally stable situation to begin with. A slope with a friction angle of 33 degrees means that once the slope angle reaches 33 degrees the slope has an approximate facator of safety of 1.0. This is just for the static case and once you include earthquake loads the factor of safety will be less than 1. Can you make the slope flatter or the wall higher to reduce the backslope?