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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