Study On Bolt Anchoring Quality Dynamic Response Character And Testing Technology

The research of anchorage quality defect detection technology of the bolt is one of theimportant research topics in the study of rock and earth anchoring construction, carrying outthe research of anchor rod firmly quality dynamic response characteristics and detectiontechnology of the anchor has important theoretical significance and engineering applicationvalue. In this paper, the work is carried out through combining the theoretical analysisnumerical calculation with field testing methods, main conclusions are：⑴Based on the elastic dynamics theory, established a dynamic response model of defectsanchor rod firmly quality, and analyzed the dynamic response characteristics of the fullanchor bolt and defects anchor rod firmly quality. Results show that the anchor boltcompletely dynamic response characteristics have spatiality and timeliness, that is to say thedisplacement and vibration velocity at the same time in different location is different and thedisplacement and vibration velocity in the same location at different times of is different too;For defects anchor rod anchor solid vibration velocity of stress wave, amplitude change isbigger, in the contact interface of different degree defects, the amplitude and velocity willoccur mutation and the more severe of the defect degree, the amplitude of the mutation will begreater.⑵Using finite element method to simulate dynamic response characteristics of thedifferent density, elastic modulus anchored body by the frequency of f=1000,2000,6000,2000,6000Hz stress wave produced by excitation wave which transmits anchor rod. Theresults show that the greater the frequency of excitation waves, the greater displacement,velocity of stress wave; there is an optimum excitation wavelength when the frequency isbetween1000~8000Hz; the density and elastic modulus of anchoring body is proportional tothe stress wave displacement, velocity and acceleration; as the excitation wave frequency issame, the smaller the density and elastic modulus of anchoring body, the more the cycleappeared because of bottom reflection. ⑶Utilizing the Fourier transform for spectrum analysis, the frequency of the power testsignal is determined; the analysis of the dynamic test signal filtering of anchor rod firmlyquality in different frequency range is finished. Results show that when the filter frequencyspectrum is in the frequency of a certain scope, the interference wave can be greatlyeliminated, and the effect of filtering is the best.⑷Field test results show that the test signal can not be identified from the power of thelength, which means dynamic test signal recognition technology of anchoring quality hasblind spots, when anchoring body length is less than or greater than a certain length. Whenthe stress wave propagates In the two-sided welding anchors, the stress wave propagates onlyto the bottom of first anchor rather than continue to spread to the second one; when the stresswave propagates in the anchors the middle part of which are welded transversely on otherstructures, the stress wave will continue to move forward without being influenced bywelding.