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15/02/2012
1
Rock Mechanics
The Most Interesting Field in Engineering
Engineering Approach to Rock Mechanics
• Define the problemp
• Determine the problem geometry
• Obtain material properties for design
• Determine loading conditions
• Conduct appropriate design,Conduct appropriate design, corresponding to the failure mode
• Install instrumentation – back analysis
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Basic Engineering• Obtain material properties for design, look
it up in the back of the book (Boring).
Engineering Rock MechanicsAttempt to obtain material properties for
design Guess? Apply Engineeringdesign – Guess? Apply Engineering Judgment (and a little geology)
Transition from Intact Rock to Jointed Rock Mass
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Qualitative vs Quantitative Rock Mass Classification
• “It was also felt that a system based more h il f d t l l i lheavily on fundamental geological observations and less on ‘numbers’ was needed” (Hoek, 2004)– A rock mass can be a very complex, highly
variable material and it is unrealistic to try and quantify the individual properties that make up a rock mass.
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Qualitative vs Quantitative Rock Mass Classification
• “If you can measure what you are• If you can measure what you are speaking about and express it in numbers, you know something about it” (Lord Kelvin)– A rock mass can be a very complex, highly
variable material The individual propertiesvariable material. The individual properties that make up a rock mass can be quantified to obtain average representative values.
If you break a complex object into easily quantified components, you’ll be able to better understand the object
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QRQD
Jnx
Jr
Jax
Jw
SRF
Load Cell
Torque Gauge
Load Cell
Friction Wheel
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RMR76
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Engineering Approach to Rock Mechanics
• Define the problemp
• Determine the problem geometry
• Obtain material properties for design
• Determine loading conditions
• Conduct appropriate design,Conduct appropriate design, corresponding to the failure mode
• Install instrumentation – back analysis
Examine2D Example File
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N’ = Q’ABC
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Failure Mode in Rock Mechanics
• If you don’t know the failure mode, you ’t d t i th t l ican’t determine the correct analysis
approach
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