Soil Nails & Rock Bolts Anchoring

Soil NailsOrigin


The technique of soil nailing began in the 1970’s.

It refers to the New Austrian Tunneling Method (NATM), which is a system about underground excavations in rock.

It has been successful utilized worldwide for excavation support and slope stabilization, and its using grows rapidly.






In the past, anchor bolts were usually inserted into drilled holes and grouted to achieve anchoring, and fixed with mechanical anchors in order to increase the resistance on the ground.


Rock:rock bolts

Rock bolts are 15 to 32 diameter steel bars inserted into 30 to 60 mm drilled holes.Rock bolt’s length is from 1m to 9m.

Rock anchor bolts can be bonded along their entire length with cement grout, or anchored at various points at the bottom of the hole using chemical resins or mechanical anchors.

Rock anchor bolts transfer loads from the unstable exterior to the confined (and stronger) interior of the rock mass.

This kind of anchor is widely used in New Austrian Tunneling engineering and underground mining.




In mines

Rock bolts reinforce the top of the cavity to achieve the beam effect with the natural earth.

In tunnels

Bolts reinforce the natural earth on the roof to create an arched effect.


Soft ground:soil nails


The systematic rock anchoring principle can achieve good anchoring effects when applied to soil layers, but the requirements for soil nails are higher.

Soil nails have a diameter of 20 to 50 mm and are inserted into drilled holes of 70 to 150 mm. The length of soil nails is generally 6 to 30 meters.




  • Stabilization of excavations
  • Embankment stabilization
  • Stabilization and renovation of land slips
  • Road construction
  • Renovation of retaining walls, tunnels


Solid Bar and Hollow Bar

Both of solid and hollow anchor bar technologies involve the insertion of reinforcing elements (reinforced concrete) into the soil/rock mass.

Solid anchor bar is typically installed into pre-drilled holes and then grouted into place by using individual grout lines. The hollow anchor bar can achieve simultaneous drilling and grouting by using a sacrificial drill bit and byusing a grouting pump to grout the hollow anchor during the drilling process.

For underground applications in loose soil/rock conditions, hollow grouted anchor bar is often used.

As labor costs become higher and higher, hollow anchor bar is widely used.


Installation of Soil Nail

  • Inserting Bar
  • Spraying Shotcrete
  • Applying Plate
  • Spraying Shotcrete



Installation of a soil nail

Stable, self-supporting soil at the excavation face: by applying reinforced shotcrete.

Large working space for drilling rig: excavation in stages.

For the Soil Nail System

High tensile and shear strength

High ductility

High bond strength

Installation of a rock bolt

For the drilling equipment

Select the appropriate drilling rig based on the project scale, working environment, ground conditions, self-drilling anchor bar size and drilling depth.

In some cases with limited headroom and smaller anchor bar sizes, such as R25 (or R32 in shorter lengths), handheld drill are also feasible.

Drilling, flushing, grouting and post grouting


Soil NailsComponents:


Load bearing or functional elements

Hollow core anchor rods/Extension couplings/Hexagonal nuts/hex nuts

Plates (Domed or flat bearing plates)

Operational elements

Drill bits/Spacer/centralizer





About Onton All Threaded Hollow Bar


OntonBolt manufactures hollow anchor rods in all configurations from 1/2″ to 3″ diameter.

We offer self-drilling anchors and soil nails and micropiles which are same as DYWIDAG Drill Hollow bars. The thread profile is standard ISO10208 rope thread (R25, R32, R38, R51). The main markets include Japan, India, Turkey, Spain, Australia, Chile, etc.

Additionally, we can provide assemblies with sleeves or coupling nuts.

OntonBolt also manufactures Trapezoidal Threaded (T30, T40, T52, T73, T76, T103)

Hollow Bars to be an alternative to Ischebeck Titan anchor bolts. Which are mainly exported to Europe and America.

Different specifications of self drilling drill rods are available with hot dip galvanized.

We can manufacture items specific to customer’s requirements. We continually research and improve our products to meet the demands of the market.

The introduction below is about Soil Nailing work, explaining the usage of the nail, where it can be used, the nailing dig required and guidelines for installation of hollow bar anchors. In fact, soil nailing works are different in each other. It depends on the engineer designs. Thus the following introduction of soil nailing is for guidance only.


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