Clay consolidation time

We typically use real bay mud for our tests. Consolidation will all depend on your layering. If you do fairly thin layers then they may consolidate in 4-8 hours for each load increment, if you do thick layers then time goes up by thickness squared. You can calculate this if you assume a reasonable cv. You can see that if you try to do a single thick layer then it takes many days to consolidate. Your total thickness can be large as long as you have the drainage interlayers.

When you construct the model from slurry you have to apply the load in stages, you can roughly double the load each time but if you apply too much load in a single step then you will fail the soil. Since you have to do staged loads then you have to consolidate each lift several times. If you're going after overconsolidated then you may have many load increments. The total time for construction depends greatly on your model, the drainage layer thickness, and the final consolidation pressure. It's not uncommon for students to spend at least a week consolidating six inch total thickness of clay.

The consolidation time on the centrifuge will be the same as in the lab, only it will be a single load increment. Thus if it takes 4-6 hours in the lab to consolidate a lift, it will take 4-6 hours on the centrifuge to consolidate after spinning up and 4-6 hours to consolidate after shaking if you want to shake again. You get a pretty good reduction in time because you're on the reconsolidation curve instead of the virgin compression curve, but it can still be a significant impact on the number of hours spinning.

It's very confusing typically when researchers first start because we always say consolidation happens N squared times faster on the centrifuge. This is true in comparing prototype times. Suppose you were to predict that a 1m thick layer of clay would consolidate in 1 year. At 30 g's, your 1m thick prototype becomes 33mm thick, and it will consolidate in under 10 hours (1 year / 900). But if you load that 33mm thick layer of clay in the press or on the centrifuge it's going to take 10 hours to consolidate in real time. It's only the prototype time that happens faster.