Rock bolts 2009.ppt
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Transcript of Rock bolts 2009.ppt
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ROCK BOLTING
Rock and Soils 2009Don Cameron
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CONTENT Introduction to rock bolting
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Rock Bolts, Rock Anchors Tension bolt
mechanical bolt
friction bolt
grouted bolt or cable
Shear bolt (dowel action)
Long or relatively short?
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Benefits of a Bolt
tension
Ta
Na
Tensile force in bolt produces greater normal force & hence joint friction and anti-sliding force, Ta
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TYPES 0F ROCKBOLTSA. Mechanically Anchored Cone forced into expanding shell @ base by
screwing nut to shank
Voids subsequently grouted
Moderately hard to hard rocks
slipping likely in VERY hard rock
Blast vibration may loosen anchor
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Digunakan untuk lubang bukaan pada batuan terkekarkan
Daerah yang berpotensi terjadinya runtuhan baji atau blok
Mudah dan cepat dalam pemasangannya
Dapat ditarik untuk memberi efek kuncian pada potensial baji yang tidak stabil
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Terbagi menjadi ( berdasarkan pengaplikasiaannya):
Ungrouted mechanicals anchored bolt• pada daerah non korosi• Untuk penggunaan jangka pendek dan
menengah Grouted mechanicals anchored bolt• Terdapat resiko korosi• Penggunaan jangka panjang• Grouted dilakukan setelah periode tarikan
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Reference: Hoek, E., Ch 14 of Practical Rock Engineering, 2007
http://www.rocscience.com/hoek/pdf/14_Rockbolts_and_cables.pdf
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TYPES 0F ROCKBOLTSB. Friction Anchored Rock Bolts (heavily jointed
rock) perlu wire mesh/shotcrete
Split-set & Swellex
1. Swellex - collapsed tube, expanded in drillhole with water pressure Pull-out resistance dependent on applied water
pressure
Expensive and temporary
http://www.swellex.com/
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TYPES 0F ROCKBOLTSB. Friction Anchored Rock Bolts
2. Split-set - collapsed tube, expanded in drillhole with water pressure borehole diameter crucial: must be slightly smaller than
split-set
no tension
bolt lengths < 3 m
www.splitset.com/rock-bolts.html
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TYPES 0F ROCKBOLTSC. Grouted Rock Bolts
Cement or resin cartridge placed in drillhole
Reobar ‘drilled’ through cartridges
Top of the bolt not bonded to the grout (wrapped in PVC tape)
Nut tensioned against anchored end
Versatile, high corrosion resistance
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http://www.rocscience.com/hoek/pdf/14_Rockbolts_and_cables.pdf
Reference: Hoek, E., Ch 14 of Practical Rock Engineering, 2007
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TYPES 0F ROCKBOLTSD. Grouted Cable Bolts Temporary support systems Untensioned fully grouted cables (used in the
mining industry) act as passive reinforcement the rock mass must be in a state of compression
during installation dilation upon shearing tensions the anchor
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Passive reinforcement - non-tensioned
Tensile force develops as slide initiates: dilational joint only (rough, undulating)
sliding shear
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Example of use of Cable Bolts Windy Point Great Ocean Road instability of 200,000 tons of rock
Sandstones, interbedded mudstones, 27° dip seaward
Problems during installation; slide moving @ 2 cm per day
Slide stopped after first 7 anchors installed 45 x 170 ton anchors, 18 to 43m long Estimated F of S = 1.07
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Summary: Rock boltsRock bolts and cables can incorporate;• mechanical anchorage• grout
Rock bolts and cables may be post-tensioned (active) or rely on the rock mass to do the work (passive)