Coefficient of Consolidation cv from Oedometer Curve

Casagrande log-time: cv = 0.197 Hdr^2/t50; Taylor sqrt-time: cv = 0.848 Hdr^2/t90. Hdr is the SPECIMEN drainage path - half the specimen height for two-way drainage, full for one-way - not the field layer. A 1 in specimen drained both ways (Hdr 0.5 in) with a Casagrande t50 of 5 min -> cv 0.00985 in^2/min = 0.0985 ft^2/day = 1.06e-3 cm^2/s. Report cv from several load increments (it varies with stress); the two methods often differ and Taylor tends higher. The oedometer data and the engineer of record govern.

Casagrande: cv = 0.197 Hdr^2 / t50. Taylor: cv = 0.848 Hdr^2 / t90. Hdr = H/2 (double) or H (single).

The coefficient of consolidation cv from an oedometer (ASTM D2435) time-settlement curve by the Casagrande log-time and Taylor square-root-time fitting methods, as compiled in Das, Principles of Geotechnical Engineering / Holtz-Kovacs / Terzaghi, by name.

The Terzaghi time factors (T50 = 0.197, T90 = 0.848) and the cv = Tv Hdr^2/t relation are standard published soil-mechanics results; the fitting times t50/t90 are the user's own oedometer readings.

Estimate. AHJ and licensed professional govern.

Field names used by the API: method, t_fit_min, specimen_height_in, drainage, cv_in2_min, cv_ft2_day, tv, hdr_in

• Casagrande (log-time) cv = 0.197 Hdr^2 / t50 (T50 = 0.197 at U = 50%)Casagrande / Terzaghi consolidation theory
• Taylor (sqrt-time) cv = 0.848 Hdr^2 / t90 (T90 = 0.848 at U = 90%)Taylor / Terzaghi consolidation theory
• Drainage path Hdr = specimen height/2 (two-way) or full height (one-way)oedometer specimen geometry
• Scope one load increment; feeds the field consolidation-time tiles with the FIELD Hdrconsistency with the time-rate tiles