Rock Mechanics Fundamentals

• Rock mechanics refers to the theoretical and applied science concerned with the mechanical behavior of rocks.
• Rock mechanics is practically applied to rock masses at scales relevant to engineering and mining projects.
• Weathered or fragmented rocks blur the distinction between rock and soil mechanics.

Rock Mass vs. Intact Rock

• Rock masses feature breaks due to joints and faults.
• Intact rock lacks joints, though micro-cracks may be present.
• Joints divide the rock mass into blocks, which are regarded as intact rock.
• Fluids, like water, are commonly found in open joints and within the pores of the rock.
• Rock mechanics addresses the orientations and characteristics of joints.
• Rock mechanics explores the properties and structure of the rock between joints, focusing on intact rock.

Practical Investigation in Rock Mechanics

• Initial geological and geophysical investigation identifies rock lithologies and boundaries.
• Subsequent drilling and excavation determine jointing patterns and the intact rock's mechanical and petrological properties.
• Measurements assess in situ rock stresses prior to excavation.
• These measurements are used for major projects like tunnel excavation and dam construction.

Estimation of Rock Mass Properties

• Various methods estimate rock mass properties based on intact rock properties coupled with the joint system.
• Quantitative estimates of rock mass quality consider the frequency of discontinuities, such as RQD.
• Engineering rock mass classifications, like RMR, Q, and GSI, offer detailed systems.
• Classifications consider the frequency, spacing, and quality of discontinuities, along with strength properties.