... bottom, 3.Designed for hard rock . Expansion shell rock bolt consists of steel shell expansion head, hollow anchor rod, grouting stopper, ... ) Drill the hole and clean2) Insert the anchor bolt to the hole bottom 3) Prestress the anchor rod ... the designed value ,use the stretching gauge of anchor bolt or spanner;5) Connect of grouting joints to ... 5/5.0/6.0length tolerance ±2.5% expansion shell rock bolt