BRIEF OVERVIEWBRIEF OVERVIEWGEOTECHNICAL GEOTECHNICAL APPLICATIONSAPPLICATIONS

OFOFROCK MECHANICSROCK MECHANICS

ROCK ROCK DURABILITY DURABILITY AND USE AS AND USE AS DIMENSION DIMENSION

STONESTONE

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Dimension StoneDimension Stone• Quarried dimension Quarried dimension

stone has been stone has been used as a building used as a building material dating to material dating to 6000 BC in Jericho6000 BC in Jericho

• Used extensively Used extensively for foundations, for foundations, bridges, aqueducts, bridges, aqueducts, road surfacing, and road surfacing, and military military fortificationsfortifications

One of the most common applications of dimension stone has been One of the most common applications of dimension stone has been construction of gravity retaining walls, usually in mountainous areas construction of gravity retaining walls, usually in mountainous areas with steep bedrock slopes.with steep bedrock slopes.

Machu Picchu, in PeruApennine highway in Italy Tioga Pass near Yosemite

• Nimrod’s CastleNimrod’s Castle was built by was built by European European Crusaders in the Crusaders in the 1212thth Century using Century using basalt blocks and basalt blocks and limestone limestone

• Earthen moundsEarthen mounds were often built were often built over over telstels, or rubble , or rubble piles, from piles, from previous cities or previous cities or citadels, to gain citadels, to gain elevation elevation advantage for advantage for defensedefense

• Low porosity Low porosity crystalline rockcrystalline rock, , such as granite, such as granite, has always been has always been desirable because desirable because of its superior of its superior durabilitydurability

• Massive rocksMassive rocks tend to be less tend to be less intensely jointed intensely jointed or weathered, but or weathered, but alsoalso

• Harder to Harder to excavate excavate

• Cyclopean masonry rock retaining wall supporting a Cyclopean masonry rock retaining wall supporting a highway in the Andes Mountains of Peru. Note tunnel highway in the Andes Mountains of Peru. Note tunnel at middle right excavated in rock to convey river flow.at middle right excavated in rock to convey river flow.

RQDRQD

• Rock Quality DesignationRock Quality Designation index, or index, or RQDRQD, was introduced by Don , was introduced by Don Deere in 1963. It judges rock quality based solely on Deere in 1963. It judges rock quality based solely on measurements of recovered rock core (above left) in 10 foot measurements of recovered rock core (above left) in 10 foot increments, based on percent recovery and percentage of the increments, based on percent recovery and percentage of the pieces longer than 4 inches. pieces longer than 4 inches.

RQDRQD• RQD = Σ pieces > 4” long (100)

total length cored

• 100-90 Excellent• 90-75 Good• 75-50 Fair• 50-25 Poor• <25 Very poor

the reported RQD value varies along the scan line of the recovered core

• The Rock Mass Rating (RMR) System, or Geomechanics Classification, was introduced by Dick Bieniawski in 1972-73. It has been continually refined, base don case studies of actual excavations.

• ““RockRock” is a subjective term. Karl Terzaghi ” is a subjective term. Karl Terzaghi arbitrarily defined hard rock as any natural arbitrarily defined hard rock as any natural material having qmaterial having quu > 4000 psi, which is same as > 4000 psi, which is same as structural concrete.structural concrete.

• Even the hardest rocks are perturbed by Even the hardest rocks are perturbed by discontinuititiesdiscontinuitities; such as these sheet joints, ; such as these sheet joints, which are essentially tensile fractures, which which are essentially tensile fractures, which form a never ending series of blocks. form a never ending series of blocks.