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 A borehole is a narrow shaft bored in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water ( drilled water well and tube well), other liquids (such as petro ...

(ground) to read the pressure.

History

A man named Louis Menard in 1955 first brought the pressuremeter to the forefront. He started the first production of it in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

in 1955.

How it works

The probe of the pressuremeter is inserted into the borehole and is supported at test depth. The probe is an inflatable flexible

membrane A membrane is a selective barrier; it allows some things to pass through but stops others. Such things may be molecules, ions, or other small particles. Membranes can be generally classified into synthetic membranes and biological membranes. B ...

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.

How it is used

The pressuremeter is used to test hard

clays Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

, dense

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

s and weathered rock which cannot be tested with push equipment. It allows engineers to design foundations that will be stable in these conditions. There are three different types of pressuremeters. The borehole pressuremeter is the most common and has a probe that is inserted into a preformed hole (borehole). The second type of pressuremeter is called a self-boring pressuremeter. The self-boring pressuremeter has a probe that is self-bored into the ground to prevent disturbance. The third pressuremeter is called a cone pressuremeter. The cone pressuremeter has a cone shaped probe that is inserted into the base of the borehole, it then displaces the soil into the cone of the probe which causes less disturbance to the soil to get a more accurate reading. Different soil types sometimes require different types of pressuremeter tests.

References

{{reflist In situ geotechnical investigations