Consolidation Degree from Elapsed Time (Terzaghi)
The inverse of the consolidation-time tile: how far a surcharge or fill has consolidated after a given time - Tv = cv t / Hdr^2, then U = 100 sqrt(4 Tv/pi) for Tv <= 0.283 else 100 - 10^((1.781-Tv)/0.933). cv 0.1 ft^2/day, Hdr 10 ft, 848 days -> Tv 0.848, U 90%; at 196 days U is only 50% (the decelerating curve, U approaches 100% asymptotically). Hdr is half the layer for double drainage (a 4x time swing). The engineer of record governs.
Formula and source
Tv = cv t / Hdr^2; U = 100 sqrt(4 Tv / pi) for Tv <= 0.283 (U <= 60%), else U = 100 - 10^((1.781 - Tv)/0.933).
Terzaghi one-dimensional consolidation theory (time factor Tv), inverted for U, as compiled in Das, Principles of Geotechnical Engineering, by name.
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