Stress measurement in rock by demountable strain gauges

Abstract

Underground mining operations require a knowledge of the stress in the rock at the peripheries of the mine workings so that we can select the correct supports, establish the likelihood of caving of the roof or walls of the workings, determine whether the rocks can be blasted, etc.In mines the stress in the rock is studied by measuring its magnitude and direction at exposed surfaces and in the solid rock. Ilivitskii and Sashurin [1] proposed a method for measuring stresses at exposures of hard rocks by partial relief from load, using glued-on strain gauges. This gluing method has shortcomings (the glue takes more than a day to set without heating). In waterlogged workings gluing is a very complex procedure and the polymerizing glue must be protected from moisture. Cold-setting glue based on epoxy resin, which polymerizes in a day under mine conditions, has a very low softening point (25-30~ therefore the load-relief hole must be drilled very carefully so as to avoid heating the rock.To eliminate these shortcomings and speed up measurements, we have proposed an experimental procedure which excludes gluing and uses demountable strain gauges. The measurement scheme is shown in Fig. 1.At the measurement site small-diameter holes are drilled at the corners of an equilateral triangle. Roof-bolts, serving as reference points, are inserted in the holes and the strain gauges tightened up between them. A load-re-, 1%

Rock Deformation Behavior Near Excavations Under the Influence of High Tectonic Stress in Coal Seam V-12, “Severnaya” Mine, JSC “Urgalugol”

“…The authors wrote down manometer and dial gauge readings [5]. After the results of the experiment were processed the authors determined the elasticity modulus, coal compression strength, values and direction of main stress vector (Table 1).…”