Page 182 - Rock Mechanics For Underground Mining

PRE-MINING STATE OF STRESS

(d) Determine the magnitudes of the field principal stresses, and their orientations
relative to the mine global axes.
(Note: This problem is most conveniently handled with a calculator capable of
solving six simultaneous equations.)

5 Measurement of the state of stress in a rock mass produced the following results:
1 , of magnitude 25 MPa, is oriented 109 /40 ;
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2 , of magnitude 18 MPa, is oriented 221 /25 ;
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3 , of magnitude 12 MPa, is oriented 334 /40 .
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The groundwater pressure at the measurement site is 8 MPa. A fault, oriented

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190 /60 , is cohesionless, and has an estimated angle of friction of = 20 .
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Comment on the consistency of this set of observations, and describe any other
subsequent investigations you might consider necessary.

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