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Rock Mechanics.pdf - Mining and Blasting

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MONITORING ROCK MASS PERFORMANCE<br />

Table 18.1 Displacement monitoring methods (after Windsor, 1993).<br />

Deformation Measurement Measurement Measurement Measurement Sensitivity<br />

Technique Access Method<br />

OBSERVATIONAL TECHNIQUES<br />

GPS E M M<br />

Terrestrial Surveying E M M<br />

EDM & Automatic Surveillance<br />

INSTRUMENT TECHNIQUES<br />

Movement Indicators<br />

E A M<br />

Axial B/F O L<br />

Shear<br />

Convergence Indicators<br />

B/F O L<br />

Wire/Tape F M M<br />

Rod<br />

Strain Meter<br />

F M/A M<br />

Resistance Strain Gauges B A H<br />

Vibrating Wire Strain Gauges<br />

Joint Meters<br />

B A H<br />

Glass Plates F M M<br />

Pin Arrays F M/A M<br />

Strain Gauges B A H<br />

Proximity Transducer F A H<br />

Fibre Optic B A H<br />

Potentiometers<br />

Extensometers<br />

Fixed Extensometer<br />

B/F A H<br />

Wire/Rod B M/A H<br />

Reference Point Sensing B M/A H<br />

Strain Sensing<br />

Portable Extensometer<br />

B M H<br />

Magnetic Anchor B M H<br />

Magneto-strictive B M H<br />

Sliding Micrometer<br />

Inclinometers<br />

B M H<br />

Fixed Inclinometer B A H<br />

Portable Inclinometer B M H<br />

Deflectometers B A H<br />

Extensometer-Inclinometer B M H<br />

Extensometer-Deflectometer B M H<br />

F = <strong>Rock</strong> Face, B = Borehole, E = Exposure, M = Manual, A = Automatic, O = Observations, L = Low,<br />

M = Medium, H = High<br />

78.5 kN to a 1.0 mm diameter invar wire stretched between an anchoring point <strong>and</strong> the<br />

instrument which is itself attached to the second anchoring point at the rock surface.<br />

The tensioning device moves the end of the wire towards the displacement gauge with<br />

a precision thread. The applied tension is read on the dynamometer. The displacement<br />

gauge has a readability of 0.01 mm <strong>and</strong> a range of 100 mm. The overall accuracy of the<br />

convergence measurements is ± 0.02 mm. Normally, these levels of readability <strong>and</strong><br />

accuracy are not required for routine convergence monitoring in underground mining.<br />

When interpreting convergence measurement results, it is important to consider<br />

the time rates of convergence <strong>and</strong> any changes in those rates, as well as the total<br />

548

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