Study On The Low Frequency Signal Anchor Bolt Of Dynamic Response Charateristics

The construction method of the technology of anchor bolt used in rock, foundation, slope, underground hole reinforcement is simple, reinforcement and economic significantly, so the technology has been widely used in hydropower, railway, mining, construction, tunnel and other fields. The engineering of anchor bolt is influenced by geotechnical engineering conditions, structural design of anchor, the interaction of anchor and rock, construction, professional skills and experience. The bolt construction also has a high degree of concealment, so finding the quality problems is difficult, and dealing with the accident is more difficult. In a word, the quality of anchor, the integrity of anchor bolt and the stress state in anchor bolt are monitored in real-time, which is necessary.The methods of numerical analysis, experimental research and signal processing are mainly used to study the propagation of low-frequency stress wave in the bolt in the paper. On the one hand, the numerical analysis method is used to simulate the bolt anchoring system, and the results were analyzed. On the other hand, the signal processing method is used to extract the feature value of data and waveforms obtained by a test. Finally, the D-S evidence theory is used to determine the quality of the bolt.1) Numerical analysis: The three-dimensional model of anchoring system is established by the ANSYS/LS-DYNA dynamic finite element analysis software. The low-frequency stress wave propagation and reflection in the anchoring system are simulated, and the simulation results are analysis.2) Bolt testing: The transient excitation force is applied on the top of the bolt, and the sensor installed at the top of the bolt receives the reflected signals. The hammers of four different materials were designed: iron head, aluminum head, nylon plus iron head and rubber head, which are as an incentive source and used to test and collect signals to the three different specifications of the steel bolt.3) Signal processing: Hilbert-Huang transform is the most effective method to analyze the nonlinear and non-stationary signals and has been applied to seismic signal analysis, speech signal analysis, fault diagnosis and other areas. The HHT method is used to extract the feature value of the signals tested, and the noise signals are removed, which is compared to the wavelet transform.4) The data extract by HHT is the defective bolt data and defect-free bolt data. In order to distinguish between the two types of data, the D-S evidence theory is used to diagnose the failure bolt.