A pressure meter used to measure groundwater pressure at a point in the ground allowing it to be quantified and, from that, the pressure head (see Equipotential Lines) and pore pressure to be calculated.
The simplest piezometer is a tube (piezo-tube) on the end of which is a perforated section (piezo-tip). The tube and its tip are lowered into a borehole whose location has already been selected on the basis of either the likely pattern of groundwater flow or the need to know pore pressure at that location. The tip is placed at an elevation in the hole where a measurement of pressure is required; this elevation is normally chosen on the basis of the geology penetrated and pattern of flow expected. The tip is then surrounded by granular material which serves three purposes: (i) to prevent the ground around the tip from collapsing into the annulus between the tip and the borehole wall and in so doing possibly creating pathways in the surrounding ground which connect that point...