SKEMA's Friction Rock Stabilizers are a hollow steel tube split lengthwise on one side. One end is tapered to allow easy entry of the tube into a hole drilled in rock with diameter smaller than the outside diameter of the bolt. The other end has a steel ring welded around the circumference to hold a face plate in place. The square face plate is pressed against the rock during installation. The plate holds the surface of the rock face in place and is often used to retain sheets of mesh screening installed between bolts. The tube compresses when driven into the smaller hole in the rock exerting radial forces gripping the walls of the hole. The bolts are designed so grip more as rock displacement occurs, generating an active support resistance. The full length of the bolt compressed in the rock provides a stable base to support up to six tons of pull on the face plate holding the roof.
MINER INSTALLING SKEMA FRICTION-SET BOLT
Friction Type Rock Bolts (Split SetTM) Bolts Roll formed steel tubing with a welded ring at the driving end. Installed in pre-drilled holes with the same rock drill. Ease of installation and low cost makes this a popular rock bolt.(FRICTION BOLTS ARE AVAILABLE FROM PHQ)
Deformed Grouted Bar Bolts Installed in pre-drilled hole. This bolt provides effective support in areas prone to seismic events or high stress changes. Often used to hang pipe or cables. (NOT AVAILABLE FROM PHQ)
Shepherds Crook Bolt Installed in pre-drilled hole. This bolt provides effective support in areas prone to seismic events or high stress changes. Often used to hang pipe or cables. (NOT AVAILABLE FROM PHQ)
Exandable (SwellexTM) Bolts Installed in pre-drilled holes. Pushed into hole and inflated with high pressure fluid. Popular bolt due to ease of installation but more expensive than Friction Type Bolts.(NOT AVAILABLE FROM PHQ)
UniBar Bolt A fully threaded bar with superior tensile strength. Installed with either cement or polyester resin. Used for permanent installations. Cost of grout makes this bolt more expensive.(NOT AVAILABLE FROM PHQ)
Sling Type Eyebolt Bolt installed in a pre-drilled hole using a wedge (not shown) Used for the suspension of air and water columns, ventilation columns, electrical cables.(NOT AVAILABLE FROM PHQ)
Threaded Rock Studs Installed with either cement or resin in pre-drilled holes This type of support is recommended for the short to medium term where long term stabilization is not planned.(NOT AVAILABLE FROM PHQ)
Mechanical Anchor Bolts Expansion Shell Bolts Used in most Canadian mines. Installed in a pre-drilled hole using the same rock drill to torque up the nut on the bolt to proper tension. Low cost makes this a popular bolt. (NOT AVAILABLE FROM PHQ)
View of Puller Assembly set up on the pull collar of a Skema friction bolt installed into a drift wall. Puller Weight 22 kg (48.5 lbs)
Miner placing the Puller Assembly onto the pull collar under the ring on friction type bolt. The hydraulic jack rests on the floor of the drift.
Miner operating the hydraulic jack to pull-test the bolt. Engineer is reading the gauge mounted on the hydraulic jack. Jack Weight 6 kg (13.5 lbs)
Skema Friction Rock Stabilizers design allows bolts to tighten should lateral rock displacement occur, enhancing yielding capabilities.
Manufacturing - A hollow tube slit lengthwise. Tapered on one end and a welded ring at the other to hold the plate. A square plate is used to stabilize the shaft and hold it in place, as well as retaining wire screen against the rock face.
Installation - The tapered end starts the tube, into a smaller hole drilled in rock and the long slit allows compression of the tube.. The compressed tube exerts radial forces which increase as rock displacement occurs generating active resistance.
Components - Consist of the tube, matching domed bearing plate, and driver tool fitting the rockdrill used to drill the holes. Drivers are available to fit jacklegs, stopers and drifters for each bolt diameter. PHQ make a hydraulic pull tester that measures the holding strength of bolts after installation, and over time. Pull collars are available by tube diameter.
Choices - Stabilizers are available in 33mm, 39mm and 46mm diameters, and in lengths to suit requirements. Bolts can be supplied in black or hot dip galvanized steel to satisfy environmental corrosive conditions.
Ground Shifts Grip Tighter - Pull tests prove the superior holding power of the Friction Rock Stabilizer system. After installation when ground shifts (often caused by blasting in the area) loosen conventional rock bolts, the Friction Rock Stabilizer tube grips more tightly. Often, within weeks or months, when the average conventional bolts becomes ineffective and require re-torquing, typical stabilizer bolts retain full load-bearing characteristics. Skema Friction Stabilizer tubes never need tightening. The tubular structure and high strength of the Friction Rock Stabilizer allows it to conform to rock displacements.
In the hole, the outer wall of the tube exerts forces against the rock over the full contact length of the tube, as well as providing support to the plate.
Full Length Support - The Friction Rock tube applies frictional properties over its full contact length; not just at the end as compared to a standard shell type point-anchor bolt.. The tube and bearing plate exert forces to hold the rock immediately upon installation.