The Design And Research Of Bolt Detector Based On Random Coding Source

In all kinds of underground engineering and slope care, anchoring technology has become the main means of reinforcement, widely used in urban transport, hydropower stations, tunnels and other engineering construction. To a certain extent, the anchoring directly determines the quality of the whole project, and because drawing detection techniques previously used can’t react real quality of anchor, it is now rarely used Acoustic stress wave reflection method is primary means of the anchor project non-destructive testing quality, also is the basic detection principle of almost all bolt instrumentation on the market.Acoustic stress wave reflection method draws on the "small strain dynamic pile testing technology" theory, and based on the one-dimensional bar elastic vibration theory. It will be measured as a bolt-dimensional linear elastic rod. When anchor the top motivated and incurred after stress waves, stress waves propagate along the shaft encountered during discontinuous interface (necking, Mud, holes, segregation, etc.) and the reflected wave is generated when the bottom bolt through the detection and analysis of the reflected wave travel time, amplitude and phase characteristics, you can determine the length of bolt and completeness. These can be attributed to a one-dimensional inhomogeneous damped wave equation in different boundary conditions and initial conditions solving. However, the use of the theory test when assessing bolt works, they would often misjudgedAfter collecting and analyzing field waveforms practice, I found misjudged and missing caused by a variety of reasons, mainly include above:1. Site construction process, the excitation signal is mainly generated by human’s hammering. The frequency and amplitude of hammering source components of randomness and strong consistency is not good;2. Acquisition time, a bolt collected only5-6times in a waveform, and the effective waveform may be less;3. Analysis just by one hammer waveform, random signal can not be removed;4. Sometimes waveform acquisition mess, testing personnel without years of testing experience, difficult to identify the judge.Based on the insufficient of audio stress wave reflection method, there are some people began to explore the electromagnetic method to do the bolt quality nondestructive testing theoretical feasibility, but there have not yet been implemented. Professor Lv Fuzai of Zhejiang University detailed description of the magnet guided wave technology with a complete bolt testing theoretical basis and some experimental results, theoretically proved that the method is feasible in the "technology-based anchor magnet waveguide design new detection methods". However, feedback from the actual project implementation point of view, there are some distance away from the engineering application.The main problem is:1. Anchor different material great influence on the measurement results;2. Detection apparatus design is more complex, generating an excitation signal with very strict requirements, and very weak received signal, typically4,000times larger can do processing, so that the internal noise of electronic circuits great influence on the measurement data;3. Data interpretation method is relatively simple, and they make a judgment to see in the time domain waveform amplitude.4.Bolt length only for a certain range the results given in, it can’t make an accurate evaluation of anchoring quality.This article describes in detail the anchor based on random coding source and detector design theory, change the past, non-destructive testing of anchoring to a single trigger and acquisition based on the idea of communication in the field of reference coding theory the quality of existing anchoring detector upgrade expansion. The operation process capture commands issued by the operator, and then by the core circuit informs the operator ready to generate random coded signals, then the operator of the bolt stress wave acoustic excitation. At the same time the signal acquisition circuit data received from the sensor, then the data transmitted to the core circuit, the core circuit for fast calculation will result intelligent feedback to the operator. Therefore, the whole system is divided into two parts:signal acquisition part and source parts.Signal acquisition part is mainly composed of processors, capture cards, and data transmission channel composition, data acquisition, analysis and display function, with built-in A/D high-speed microcontroller collected after passage through the FIFO data to the processor for processing and display works. Transmitter+excitation power source using the acoustic transducer means, the voltage rise together with the transmitter, through the power of the acoustic wave transducer converts electrical energy into vibratory energy.First, the use of reasonable selection of modern electronic technology circuit design, complete equipment and data acquisition circuit signal processing circuit, and then in the laboratory production of a plurality of anchor model known parameters, and use the instrument to measure and analyze them, according to The results of the emission and adjust the instrument acquisition parameters. Then the instrument at the construction site anchor testing and feedback through on-site and computer simulation of the results were analyzed to determine which is suitable for use in the field of fast intelligent evaluation algorithms.A large territory of several groups Pass tunnel contrast test done to prove that the anchor based on random coding focal detector feasibility, but also exposed a number of deficiencies. Such instrumentation is not efficient, on-site measurement and data processing difficulty is inversely proportional to the quality of the instrument causes excessive power dissipation and limited endurance. This reflected the lack of the pilot put forward own ideas, and then after the time to perfect.This study proposed on "code source technology" is a reference in the field of communications coding theory, and base source, acquisition and processing audio on stress wave reflection method to improve it. Use with electric excitation source code to accelerate anchor detection speed, reduce construction strength, improve signal to noise ratio collected and evaluated by writing intelligent algorithm to achieve on-site measurement and post-processing to give some guidance on the purpose, in a miscarriage of justice, and to some extent overcome missing.