A pressuremeter is a meter constructed to measure the “at-rest horizontal earth pressure”. The pressuremeter has two major components.The first component is a read-out unit that remains above ground. The second component of the pressure meter is a probe that is inserted into the borehole (ground) to read the pressure.
The probe of the pressuremeter is inserted into the borehole and is supported at test depth. The probe is an inflatable flexible membrane which applies even pressure to the walls of the borehole as it expands. As the pressure increases and the membrane expands, the walls of the borehole begin to deform. The pressure inside the probe is held constant for a specific period of time and the increase in volume required to maintain the pressure is recorded. There are two types of tests that can be performed with the pressuremeter. The stress controlled test increases pressure in equal increments while the strain controlled test increases the volume in equal increments.