Measuring stresses in a hereditary-elastic medium by means of photoelastic sensors

Abstract

The operation of a photoelastic sensor outside the zone of influence of extraction operations can be represented as follows. After the drilling of an isolated borehole of small diameter and the installation of the sensor in it, the latter operates in combination with the rock, i.e., reacts to changes in its state of stress and deformation caused by the drilling of the borehole. If the rock has creep properties, the action of the sensor will be the same as the action of an elastic ring support in a circular working with total cohesion with the solid rock, as described in [1]. In this case, the stresses in the sensor due to the creep properties of the rock will take [1] the following form:%0=--'if-3 R' ---~--a-1 r 2 --3 2r' J (1--k) sln20.(1)The coefficients in (1) depend on the elastic constants ax, bt, a-l, b_l, as, b-s of the sensor material and rock, the ratio between the internal and external diameters of the sensor, the creep parameters of the rock, and the time.It is known that the stress components o r, o 0 , rr0 at any point in an elastic sensor are related as follows to the maximum tangential stresses Vma x by the elasticity relation:~lll aX --

Photoelastic sensors

“…The following are distinctive of the photoplanimetric method, which has come into widespread use ( [2,3]) in studies associated with measurement of lump size: simplicity, ease of operation, and descriptiveness.…”

Interaction of a photoelastic transducer with an elastic-hereditary medium

“…They can react not only to elastic deformation of the solid rock, but also to creep deformation [1]. In this article we shall discuss the theory of interaction of a transducer with a rock mass possessing elastic-hereditary properties.…”