Research On Fractal Mechanism Of Bolt Anchor System Stress Wave And Its Application

Currently, non-destructive testing technique detects Bolt anchoring quality, work load and other aspects are still using conventional stress wave reflection method, by studying the bolt anchoring system stress wave microscopic detail characteristic, calculation and analysis consolidation wave speed,fundamental frequency and other methods, comprehensive judgment bolt anchoring quality and working load. However, the force of the bolt anchoring system is quite complex, resulting in bolt anchoring system exhibits a waveform corresponding complex, bottom end reflection is difficult to identify,which has brought great difficulties to the traditional detection methods, and become a technical problem to be solved urgently.To solve this problem, this paper makes a deep research on the propagation theory of stress wave in the anchor bolt, found the anchor system of stress wave is composed by a variety of harmonic wave and its waveformcomplex, but the repeated experiment can be found, the stress wave characteristic parameters(frequency, amplitude, etc.) in accordance with the rules of statistical self similarity in fractal theory, and fractal theory it is a powerful tool for the analysis of such complex graphics.The research object of fractal theory is complex and variable nonlinear geometric shape. In this paper, the fractal theory is introduced to the field of nondestructive testing of bolt, analysis of the spatial distribution characteristics of stress wave in anchorage system from the macroscopic angle. By collecting the stress wave signal of anchor system under different anchoring qualities and different working load, analysis of the correlation between the fractal box dimension of the waveform and the quality of anchorage and the working load. The main work and conclusion are given in this paper:1) The characteristics of stress wave in the anchorage system are analyzed in depth, combined with the scope of application of fractal theory, based on the application of fractal theory, the rationality and feasibility of the application of fractal theory to study the stress wave of anchorage system is proved theoretically, a new way of thinking is put forward for the nondestructive testing technology of anchor bolts;2) Based on the characteristics of stress wave and the fractal theory and the actual data collection, a mathematical model of the box dimension is established for the stress wave shape of the anchor system, using MATLAB software programming to calculate the stress waveform box dimension values;3) In order to get the relationship between the stress wave box dimension and the anchorage quality of the anchor system, the experimental study is carried out, the relationship between the box dimension and the parameters is studied by the design of the anchorage length of the anchor bolt, the bond quality of the anchorage end and the ultimate bearing capacity of the anchor bolt, the effect of anchorage quality of anchor bolt on the dimension of box dimension is analyzed comprehensively: The longer the anchorage length, the smaller the box dimension numerical; The better quality of end anchorage bond, box dimension is smaller; When the bolt is in the ultimate bearing capacity under the condition of dimension of peak;4) The bolt working load is closely related to the stress wave box dimension of the anchor system. With the increase of the working load of the anchor bolt, the value of the stress wave box dimension increases, when the bolt reaches the ultimate bearing capacity, the value of the stress wave box dimension reaches the maximum value, with the bolt is pulling out failure, the numerical value of stress wave box dimension decreases;5) When the working condition of the anchor bolt occurs, the stress wave box dimension of the anchor system is numerically corresponding to the occurrence of the mutation. When the bolt is started by the free state, the box dimension value will decrease rapidly, and there will be a catastrophe; When the bolt is in the transition from the normal working state to the failure state, the value of the box will decrease rapidly, and the fault occurs.