Dear plaxis,
when obtaining earth pressures behind a retaining structure from plaxis by using a cross section to get the sigma xx, in a pseudostatic analysis phase, the obtained earth pressures are a total right?
Meaning that, to obtain only the seismic correspondent, one has to subtract the corresponding static phase right?
Dear Abdirahman,
Thank you. This is helpful.
Dear Dennis Waterman Abdirahman Yasin
I had the same question regarding the matter. When we perform dynamic analysis of a retaining wall using an acceleration-time data in the following sequence shown below,
To obtain only the lateral seismic earth pressures exerted on the wall, we can take a vertical cross section just behind the wall. The obtained lateral pressures in phase 2 are the total earth pressures (static+dynamic) right? As in, to obtain the seismic component only, we would subtract, phase 2 (seismic)-phase 1 (static) to obtain only seismic earth pressures, right?
Dear Jamal,
I think what you stated is correct according to me unless the other guys disagree. However, beware of the sigma xx value (for effective and total stress), you have to select it according to your problem and situation in hand. For example, if you perform drained analysis for sand soil in the absence of water table, the total and effective sigmaxx will be more likely equal. But, this will change according to the drainage type, presence of water table,..etc.
Thank you.
PLAXIS doesn't distinguish between static and dynamic components of stresses. There are stresses in a static analysis and stresses in a dynamic analysis....and that's it. If you would like to substract those two to see how much a seismic load changes the stresses that is of course perfectly fine, but internally there is no consideration of static and dynamic part.
With kind regards,
Dennis Waterman