Photoelastic sensors

Abstract

An annular photoelastlc sensor is used for measuring the stresses and strains in rocks and consists, in the slmplest case, of a cylinder made of optically sensitive material (usually silicate glass, less often transparent polymers) which has an axial aperture of small diameter and a mirror layer on one of its end surfaces. The sensor is placed in the borehole, glued to its walls by its lateral cylindrical surface, and deformed together with the surrounding medium. The stresses (or strains) arising in the sensor are proportional to the change in the stresses (strains) in the surrounding material.