This standard specifies the method for conducting in-situ pull-out tests on grouted anchor bars and rock bolts. It details the required apparatus, testing procedure, and reporting of results to determine the bond strength and load-displacement characteristics of the rock anchor system.
Method of conducting a pull-out test on anchor bars and rock bolts
Quick Reference Values
Minimum bearing plate thickness25 mm
Loading rate not to exceed10 kN/min
Displacement measurement accuracy (dial gauge)0.01 mm
Pressure gauge accuracy2 percent of the maximum test load
Minimum duration for holding each load increment2 minutes
Key Formulas
Bond Stress = P / (π * d * L) — where P is pull-out load, d is bolt diameter, and L is bonded length
Practical Notes
Ensure the reaction frame is rigid and its supports are placed far enough from the bolt head (typically >2 times the bonded length) to not influence the rock failure cone.
A spherical seating is crucial to avoid eccentric loading, which can lead to premature or incorrect failure readings.
Properly isolate the unbonded (free) length of the anchor to ensure the test measures the bond strength of the intended grouted section only.