Research On Non-destructive Testing Technology Of Anchor Rod Anchorage

As for the stability of roadway surrounding rock,bolt support has become one of the most important support methods for the stability control of roadway surrounding rock due to its stability,high efficiency,economy,and convenient construction.The non-destructive testing of anchor bolts mainly focuses on the detection of anchor bolt length and the detection of defects in anchoring sections,but there is little research on non-destructive inspection of anchor bolt anchoring force.Based on the existing theory of non-destructive testing of anchors,this paper uses theoretical analysis,numerical simulation and laboratory tests to systematically study the technology of non-destructive testing of anchoring forces of anchors.The main results and conclusions are as follows:(1)By summing up and deriving the previous formula for the anchor bolt anchoring force,the anchor bolt anchoring force calculation relation is obtained;the anchor bolt anchoring force detection system is optimized and two devices are designed: nondestructive inspection Waveform stable excitation device and continuous beam-based extension rod device make up for the lack of non-destructive testing of anchor anchoring force.(2)Based on FLAC3 D numerical simulation software,numerical models of stress wave propagation in free and anchored bolts were established,and the optimal excitation point was the center position of the end of the bolt.The change of the acquisition point affected the lateral stress waveform and longitudinal stress The influence of the wave can be ignored;the main frequency value is obtained through a combination of time and frequency domain analysis,and the anchoring force calculation formula is used to obtain the anchoring force under different working loads;The ultimate anchoring force was obtained.The comparison between the anchoring force calculated from the simulation data and the ultimate anchoring force obtained by the drawing simulation shows that the two are consistent.(3)Through laboratory tests,it is verified that the optimal excitation point is the center position of the end of the anchor rod;the prestress can increase the peak value of the waveform during the propagation of the stress wave.When the peak value is too large,the anchoring start position can be identified.Have an impact;the peak pulling force in the pull-out test is the anchoring force;the type of anchoring material has an influence on the pull-out displacement of the anchor rod;the anchoring force calculated from laboratory test data is consistent with the anchoring force calculated by numerical simulation,it is further explained that the nondestructive testing method and calculation formula of the anchoring force can be used to evaluate the anchoring force of the anchor rod on the spot.