Soil nails & Rock bolts
Most of the time, these anchors are created using bars inserted in a bore hole and held in place using grouting or a mechanical anchor. Their purpose is to improve the resistance of the ground.
Soft ground: soil nails
Soil nails are 20 to 50 mm diameter bars, inserted in 70 to 150 mm bore holes. They are generally over 6.00 m long and may be as much as 20 m. They are bonded along their entire length by cement grouting. They are said to be “passive” and are subjected to tensile, bending and shear stresses by the movement of the ground.
Rock: rock bolts
Rock bolts are 15 to 32 mm diameter bars, inserted in 30 to 60 mm bore holes. They are generally between 3.00 and 6.00 m long. They may be bonded along their entire length by cement grouting or anchored at various points at the base of the hole using resin or a mechanical anchorage.
Anchors with continuous grouting are said to be “passive” and are subjected to tensile and shear stresses by the movement of the ground. Bolts with grouting at various points (resin or plug) are often prestressed by tightening with a wrench or a jack.