Pressureometer
Introduction
The pressuremetric test is one of the "in situ" tests carried out to carry out a geotechnical reconnaissance.
It consists of applying increasing radial pressure to the walls of a borehole, whether or not it reaches the limit condition of ground failure. To do this, the test element is introduced into the previously drilled borehole. This consists of a cylindrical cell, with a flexible side wall, to the interior of which, once placed at the desired depth, pressure is applied by injecting a fluid, measuring the radial expansion of the wall as a function of the applied pressure.
The first device of this type was patented by Louis Gabriel Ménard in the 1950s, and is still used today with some variants. In its simplest versions, pressure is applied by injecting a liquid, and the radial deformation of the wall is measured indirectly by the volume of injected liquid, assumed to be incompressible.
In some devices, designed for testing rocks or hard soils, the pressuremetric cell incorporates touch sensors to directly measure the deformations, which are small. In this case, the fluid injected to measure the pressure may be a gas. Rock pressuremeters are usually called "dilatometers", although there is some confusion regarding the use of both words, which are otherwise equivalent.
The usefulness of this test lies largely in the fact that there are simple analytical solutions, both in elastic range and in failure, that allow the test to be properly interpreted, especially in clay soils (load without drainage).