Abstract: The invention relates to a process and a device for casing a borehole made in a porous medium for measuring the pressure of the interstitial fluid, comprising the positioning, in the borehole, of a tube of which at least one section, located at the altitude of the measurement to be effected, possesses radial orifices along one of its generatrices, a porous band between the borehole wall and the outer surface of the section, at the level of said orifices, and a supple inner membrane in the form of a sleeve fitted on the inner face of the tube, the filling of the tube for applying the membrane against its wall and of the space included between the tube and the borehole to saturate said porous band, and the substitution of the outer liquid by a cement grout which bonds the tube to the walls of the borehole in all its zones exempt of porous band.

Abstract: A device for measuring movements or deformations has at least one pair of variable reactance movement pick-ups, each pick-up comprising transducer elements whereby a modified inductive or capacitive reactance signal is generated by each pick-up in response to the movements or deformations. The variations of the reactances of the two pick-ups are arranged to be equal but opposite. An electrical oscillator is connected alternately to the two pick-ups by automatic switching elements, and each pick-up alters the oscillation frequency in dependence upon the variation of its reactance. The required measurement is derived from the difference between the two altered frequencies.