TABLE OF CONTENTS The following notation is used in this chapter:
| Symbol | Definition |
|---|---|
| a | Inside area of standpipe |
| A | Cross-sectional area of soil specimen |
| h | Total head |
| h e | Elevation head |
| h p | Pressure head |
| ? h | Change in total head |
| i | Hydraulic gradient |
| k | Coefficient of permeability, also known as hydraulic conductivity |
| k 20 | Coefficient of permeability, adjusted to a temperature of 20 C |
| L | Length between two points, corresponding to ? h |
| n | Porosity of soil |
| Q | Total discharge volume |
| t | Time |
| T | Temperature |
| v | Superficial velocity |
| v s | Seepage velocity |
Permeability is defined as the ability of water to flow through a saturated soil. A high permeability indicates that water flows rapidly through the void spaces, and vice versa. A measure of the soil's permeability is the coefficient of permeability, also known as the hydraulic conductivity. The coefficient of permeability can be measured in the laboratory by using the constant head permeameter or the falling head permeameter, which is discussed in Sec. 12.2. The coefficient of permeability can also be determined from field tests, which are discussed in Sec. 12.3.
Figure 12.1 (adapted from Casagrande) presents a plot of the coefficient of permeability versus drainage properties and type of soil. Also indicated in Fig. 12.1 is the type of permeameter apparatus best suited for the measurement of the coefficient of permeability. The bold lines in Fig. 12.1 indicate major divisions in the coefficient of permeability. A coefficient of permeability of about 1 cm/s is the...
