| Rock Bolting has the advantages of low cost and simple construction, and has beenthe main form of support for coal mine roadways. The non-destructive detection of thequality and performance of rock bolt has been one of the key research directions athome and abroad. Based on the principles of structural dynamics, the longitudinal andlateral dynamics characteristics of the rock bolt structural system has been studied herevia theoretical analysis, experimental research and field testing. Then, thenon-destructive detection method of rock bolt quality was proposed, and the detectionsystem was designed and applied in Xishan mining area. The main research work andachievements are as follows.(1) The longitudinal vibration mechanical model of elastic waves in rock boltstructural system is established, based on the dynamic theory. According to themechanical model, the reflection and diffusion character of elastic wave at theanchoring interface and bottom of rock bolt is studied. The results show that thelongitudinal elastic wave has a reflected wave with an inverting phase at the anchoringinterface, and a reflected wave with a same phase at the bottom of rock bolt. Then, thenon-destructive detection method of free length and anchorage length of rock bolt isproposed.(2) The lateral vibration mechanical model of the anchoring system is established,and the influence of the rock bolt axial force on the dynamic characteristics of theanchoring system is analyzed. The results show that the horizontal natural frequenciesof the anchoring system increase with the increase of the rock bolt axial force. Themechanical response of the interface between the pallet and surrounding rockdetermined the relation between the horizontal natural frequencies and axial force.Then, the non-destructive detection method of the axial force of rock bolt is proposed.(3) A non-destructive detection system is developed through modular designmethod. The system includes exciting module, signal acquisition module, dataprocessing module and the smart identity module. Based on laboratory and field tests,the components and parameters of the detection system are determined, such as shockmethod and the sampling frequency, etc.(4) In order to test and verify the function of the detection system, anon-destructive detection experimental system and simulated roadway are designed in the laboratory. The experimental results show that the detection system proposed heremay effectively detect the free length and anchorage length of rock bolt, and the erroris within2%. The lateral vibration frequency of the anchoring system is closely relatedto the axial force of rock bolt, and the relation is influenced by the character of thesurrounding rock. Based on the experimental results, the automatic recognition forcharacteristic length of rock bolt is proposed, and the detection method of the axialforce under different conditions of surrounding rock is put forward.(5) The engineering application is carried out in two typical coal mines in Xishanmining area, which are Xiqu coal mine and Duerping coal mine. The rock bolts inseveral roadways from the previous coal mines are detected and monitored. The resultsshow that the detection system developed here is practical and reliable. The rock boltlength detection accuracy rate is more than95%and the axial force detection may givefast and intuitive results. Based on the field testing results, an evaluation system for theanchoring quality is presented according to the special geological conditions in Xishanmining area. The evaluation system may give the statistical regularities and distributionof anchoring condition. At last, some assessment and suggestions are proposed for theanchoring quality in the detected roadways.The results of this study may not only provide basic theoretical support for rockbolt non-destructive detection, but also provide technical methods for evaluation on therock bolt support.This thesis has106figures,23tables and126regferences. |
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