Geomechanics and Ground Control · Geomechanics · 2 marks · Numerical answer
A120 Ω strain gauge with gauge factor2.0 is bonded longitudinally to the110 mm rock specimen shown. Resistance-change magnitude at the end of the compression test is0.5 Ω. Find shortening magnitude in mm to two decimals.
Gauge factor GF=(ΔR/R)/ε. Thus strain magnitude is ε=0.5/(120×2)=0.0020833. Multiplying by the110 mm specimen length gives shortening0.229167 mm, or0.23 mm. The source dimension is110 mm; use that full specimen length rather than the gauge’s drawn length.
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