Drained vs. Undrained: Reduce the Load on Clay from Existing Condition

JHeisenberg · May 28, 2024

Example soil profile:

0-15' Sand
15-20' NC Clay
20'+ Sand

You excavate to 10'. Replace with material that weighs 1/2 of much as the excavated material.

Can you assume the clay layer will behave as drained? It seems like to me it would partially depend on how much time is between the excavation and the replacement?

EireChch · May 28, 2024

You will have undrained elastic heave due to stress relief and then some minor amount of swelling due to the soil drawing in moisture. Both will actually be very minor as NC clays dont heave as much as OC clays do due to low/zero preconsolidation stress.

If you reload you will stop some some if not all the heave.

geotechguy1 · May 28, 2024

If you re-load it rapidly, even if the weight is half, do you not still end up on an undrained shear stress path?

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Drained vs. Undrained: Reduce the Load on Clay from Existing Condition

JHeisenberg

Geotechnical

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EireChch

Geotechnical

geotechguy1

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