Define consolidation terms

Consolidation (settlement): the gradual decrease in volume of a saturated soil (clay) under a sustained load, caused by the slow expulsion of pore water and transfer of load from water to soil skeleton. It takes place with time and produces settlement.

Degree of consolidation, $U$: the ratio of the consolidation (settlement or pore pressure dissipation) that has taken place at a given time to the total expected consolidation.

$$U_z = \frac{u_0 - u_z}{u_0}, \qquad U = \frac{S_t}{S_{final}}\ \ (\text{or in percent})$$

Pre-consolidation pressure (maximum overburden pressure), $\sigma'_c$: the maximum effective vertical stress that the soil has experienced in the past. It is determined from the $e$–$\log\sigma'$ curve (Casagrande's method).

Over-consolidation ratio, OCR:

$$OCR = \frac{\sigma'_c}{\sigma'_0}$$

where $\sigma'_0$ is the present effective overburden pressure. $OCR = 1$ for NC clay and $> 1$ for OC clay.

Coefficient of consolidation, $c_v$: a soil property giving the rate of consolidation:

$$c_v = \frac{k}{m_v\gamma_w} = \frac{k(1+e)}{a_v\gamma_w}$$

Its unit is m²/s or cm²/s. A high $c_v$ means faster consolidation. It is found from the time-settlement curve of the oedometer test.