Rock anchors or rock bolts is a long anchor bolt, for stabilizing rock excavations,which may be used in tunnels or rock cuts. It transfers load from unstable exteriors to the confined interior of the rock mass.

Steel bolts are provided in holes drilled into stable rock to assist in supporting load of loose rock. In case a suspended lacks sufficient strength, it sags and tension cracks are developed.

When these cracks get further developed, it weakens the suspended strata and rock begins to fall. In case the rock is very weak, only rock bolting is not enough, it requires additional square mesh netting for preventing falling of small stones from weathered rocks.

Method of construction is done in following stages:

1. Drilling through overburden rock

2. Water proofing of holes

3. Fabrication of anchors

4. Lowering anchors

5. Fixed length grouting

6. Stressing of tendon.

v. Applications: ground anchors are used in civil engineering for the following,

1. To resist lateral thrust on retaining walls and in situ diaphragm walls

2. For stabilizing of slopes and landslides.

3. To resist uplift on basements and other foundations

4. To strengthen masonry and concrete dams

5. For testing of large diameter piles.

Diagram: the diagram below shows rock anchors used inside a tunnel.