A settlement cell is a device used to monitor settlements in embankments, fills, and foundation soil. It reports settlements of a discrete point, as opposed to a settlement profile.
The settlement cell consists of three components: a liquid filled tube, a pressure transducer, and a reservoir of liquid. One end of the tubing is connected to the pressure transducer, which is embedded in the soil. The other end of the tubing is connected to the reservoir, which is located at a higher elevation on stable ground, away from construction activity.
The transducer measures the pressure created by the column of liquid in the tubing. The height of the column is equal to the difference in elevation between the transducer and the reservoir. As the transducer settles with the surrounding soil, the height of the column increases and the transducer measures a higher pressure.
Settlement is calculated by converting the change in pressure to millimeters or inches of liquid head.