Research And Application About The Nondestructive Testing Technology For Tunnel Bolt Anchoring Quality

Rock bolt as a most commonly means of the tunnel primary support, has been widely used in many field of engineering such as highway, railway and water conservancy. In order to detect the effect of the rock bolt used in engineering, to avoid causing significant engineering disasters, nondestructive testing for anchor bar has become one of the hot topic now. This thesis is base on the theory of nondestructive testing, and combined with the analysis of the model test and field test data, through contrastive analysis, mainly conclusions are:(1) According to theoretical analysis, and combined with model test and engineering practice, the test results such as the curve shape of waveform, Spectral curve features and the change of phase characteristics and energy can well reflect the details of the anchorage system. The result show that the amplitude attenuation for the test signal was homogeneous and only one dominant frequency exist in the spectrum curve if the quality of the anchorage system is better. On the contrary, there will be more dominant frequency in the spectrum curve and the small difference between the dominant frequencies when the quality of the bolt bonding system is worse. The curve shape of waveform and phase diagram will occur mutation in the position of the defect in the bolt bonding system the more severe of the defect degree, the amplitude of the mutation will be greater.(2) According to the model test and engineering practice, the signal of the nondestructive testing are easily influenced by the interference from outside, we should choose a appropriate for the frequency filtering, and the range must include the dominant frequency, the filtered waveform should be similar to the original waveform.(3) According to the model test and engineering practice, when the anchorage system has defect, the range of the wave velocity is between anchor in the Free State and anchorage completely. So we can evaluate the quality of the anchorage system according to the wave velocity.(4) According to the model test and engineering practice, the effective test length of nondestructive testing will change with the change of the surrounding rock and compactness. The accuracy of the effective length will be better if the level of surrounding rock or compactness is better. Defect can cause serious interference to the reflection wave from the bottom, if there exist many defects in the anchorage system, we can’t even identify the reflection wave from the bottom. The accuracy of the effective length will decrease with the length of the anchor, in other word, we can not identify the signal from the power of the length when the length of the anchor reaches a certain value. So when testing long anchor, we should consider the applicability of the method of stress wave.