| Rock bolts have been widely used in the field of slope,tunnel,mine roadways and underground works because they are featured with simple constructing process and low cost.The quality of anchor bolt directly affects the quality of the project,thus bolt detection is an indispensable link in the whole anchorage project.At present,the commonly used detection methods include drawing method,torque wrench method and drilling coring method,etc.However,they are destructive and can destroy the anchorage structure of rock bolts.In recent decades,the non-destructive testing technology of rock bolts has been developed mainly by ultrasonic method,stress wave method and guided wave method.The study of stress wave method was started earlier,while ultrasonic guided wave method is still in the experimental stage.The nondestructive testing methods for anchoring quality of these two kinds of anchor bolts are mature in theory,but there are still many problems yet to be solved in practical applications.At present,no machine used in coal mine can accurately and reliably detect the anchoring quality of the anchor rod.Based on this,the paper presents some researches about ultrasonic guided wave method and a nondestructive testing machine for anchoring quality has been designed and developed based on theoretical model with the help of a serious of experiment.The main work of this paper is as follows:1.The theoretical basis of nondestructive testing technology for anchorage quality of anchor bolt based on wave guide method is studied.The theoretical model of end anchor bolt and bottom end-fixed anchor bolt under transient impact is established.By analyzing the propagation mechanism of guided waves in the anchorage system,the theoretical basis for the development of the detector is provided.2.The development process of nondestructive testing machine for rock bolts bonding integrity based on ultrasonic guided wave is introduced,including the development of hardware and software and the machine prototype is made.The power amplifying module of the detector is improved,which can amplify high frequency guided wave signals that range from 2MHz to 6MHz up to 30 dB and reach a small size but large output power requirements of broadband linear amplifier circuit.3.The end anchor bolt anchorage model is made,and the nondestructive testing machine is used to test the model.The test proved that the nondestructive testing machine can measure total length and anchorage force of rock bolt and evaluate anchorage quality.The accuracy and stability of the testing machine are verified,which meets the requirements of practical engineering. |
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