Borehole extensometer for monitoring relative mass displacements

Abstract

A device positionable in a borehole for monitoring relative mass displacements axially along the borehole between at least two spaced-apart anchor points, comprises at least two retrievable anchor members arranged in spaced-apart opposite relationship to define the at least two anchor points, the anchor members each having radially displaceable borehole wall contacting means and including mechanical means for radially outwardly displacing the borehole wall contacting means to engage the borehole wall and thereby fix the anchor member in the borehole against the wall thereof. A linear displacement sensing means is arranged between the anchor members, the displacement sensing means being connected to one of the anchor members and including an elongated axially movable sensor element, the sensor element being normally biased in a direction toward the other anchor member for contact engagement therewith. Relative mass displacements are transmitted to the sensor element and are measured by the displacement sensing means as a variation in distance between the anchor members within the borehole.

Dependencies are inferred from the claim text.