What is Rock Reinforcement?
Rock reinforcement is widely used in tunnels and surface and underground mines. A large number of proprietary products are available in various configurations of components. It provided support to the rock structures to improve its stability and load carrying capacity .
Rock reinforcement is used to pre-load the foundation.It can be used to provide a reaction during the pile load test.Rock reinforcements (Rock Anchors) are used to anchor the suspension cables and guy wires for the bridges.It helps to tie down the wire cables with the foundation under the sea.Uplift caused in transmission towers, foundation and hydraulic structures due to lateral forces is resisted by rock reinforcement.Rock anchors can be used to support sheet piles.
There are different types of supports that are used for improving the responses of rock mass or as reinforcement
- Rock Bolts
- Rock Anchors
- Rock Dowels
Rock Bolts :
Rock bolts have a friction or grout anchor in the rock and are tensioned as soon as that anchorage is attained to actively introduce a compressive force into the surrounding ground. This axial force acts upon the rock mass discontinuities thus increasing their shear capacity and is generated by pre-tensioning of the bolt. The system requires a “bond length” to enable the bolt to be tensioned.
Different type of rock bolts are used, like
Grouted rock bolts
Mechanically anchored rock bolts
Grouted cable bolts
Friction anchor rock bolts
Rock Anchors
Theyare high tensile strength bars or strands pre-tensioned by anchoring at the end of bore hole. Rock anchors are provided when compressive, uplift or pullout or laterial supports are required to stabilize a structure or rock mass on ground or underground —
-Un-tensioned anchors – Passive type and buildup tension progressively with the deformation. Passive ones develop increasing support with the deformation of rock —
Tensioned anchors – Active type, resist its movement and failure in shear. These anchors supports fully and immediately
Rock Dowels
Rock dowels are passive reinforcement elements that require some ground displacement to be activated. When displacements along discontinuities occur, dowels are subject to both shear and tensile stresses.
Theseare steel rods installed without any pre-tension- forming a column in a cement grout or resin to add to shear resistance on the failure plane or on a joint plane