Purpose and Installation of Rock Anchors

What You'll Need
Sheathed, threaded rock anchors of your choice
Appropriate drill and bit
Grouting material
Bearing plate
Restraining bolt

Rock anchors are used commonly as part of retaining walls, and as part of a system to resist movement of a foundation. Most rock anchors consist of a pre drilled hole that is filled with grout material. A threaded steel anchor bar that is sheathed and is then inserted into the grouted hole and is tensioned to the appropriate specifications of the particular job. There are many sizes and weight capacities of rock anchors depending on whether they are for small house foundation type jobs or for retaining large structures such as bridges. Either way the use and installation are largely the same.

Step 1 - Drill Your Hole

Use the appropriate size and type of drill for the material you are drilling into and the size of rock anchors that you will be using. You may need to drill through old, loose and unstable materials and into solid materials to install your rock anchor firmly in place. Oftentimes some sort of casing may be used in the instance of unstable materials or crumbling foundations.

Step 2 - Inject Grout

When injecting your grout it is important to first clear the drilled hole of as much debris as possible. Filling the drilled hole with grout from the bottom up through the top will also help assist in clearing the hole of debris. To avoid mess leave an estimated amount of space at the top of your drilled out anchor hole free of grout to account for expansion when your actual rock anchors are inserted.

Step 3 - Insert Threaded Sheathed Rock Anchors

Before grout sets, Insert your sheathed, threaded anchor down into the grouted anchor hole to a depth that leaves the amount you want to work with sticking out of the hole. The sheath is to keep the threaded anchor from bonding with the grout material as it dries therefore making it nearly impossible to turn or tension. Once the grout has set up, remove the sheath.

Step 4 - Install Bearing Plate

Once your grout has set up and your rock anchors are properly installed it is time to attach the steel bearing plate to the outside surface of the anchored material. This plate will be square and will have a hole in the center for your threaded rock anchors to fit through. Once placed over the anchors and bolted in place there will also be a retaining nut that will screw down onto the threads of your rock anchors. Together with the bearing plate this not will allow you to tension the rock anchor once installed.

Step 5 - Tension the Anchor Appropriately

At this point you can pull the anchor to a prescribed tension with your retaining nut and then lock in place appropriately to avoid future movement. This will provide rock anchors that are incredibly strong and able to withstand great amounts of tension and weight.