| Anchor rods and anchor cables are commonly used as a support structure in containment projects to strengthen and stabilise the surrounding rock to ensure its stability and safety.To ensure that the working condition of anchor rods and anchor cables meets the design requirements,their axial forces need to be monitored and tested regularly.Based on contact mechanics and non-linear vibration theory,this thesis investigates the characteristics of non-linear vibration of anchor rod and anchor cable anchorage systems using theoretical analysis,finite element simulation,indoor tests and field tests.The thesis proposes a real time axial force non-destructive testing method for anchor rods and anchor cables based on the non-linear vibration characteristics of locks and pallets,which is validated and applied in the laboratory and underground in coal mines.The results show that the method can achieve real-time axial force nondestructive testing of anchor rods and anchor cables and evaluation of the stability of the surrounding rock.The main research contents and conclusions of this thesis are as follows:(1)The non-linear vibration characteristics of the anchor rod anchorage structure system were analysed,the influence of the axial force on the intrinsic frequency and the relationship between the intrinsic frequencies of the pallet and the nut were revealed,and a method for the detection of the axial force of anchor rods and anchor cables based on the vibration characteristics of the nut/locker and pallet was proposed.(2)Indoor tests were carried out to analyse the influencing factors of the non-linear vibration characteristics of the nut and pallet,such as knocking force,axial force and excitation mode,to reveal the relationship between the vibration characteristics parameters of the pallet and nut and the axial force,and to verify the feasibility of the axial force detection of anchor rods and anchor ropes based on their vibration characteristics parameters.(3)Field tests were carried out to test the stresses of the anchor rods/anchor cables during the boring and stabilisation periods of the roadway.Based on the results of the anchor rod/anchor cable axial force testing,an axial force analysis model was established to obtain the evolution of the anchor rod/anchor cable stresses in the roadway under different conditions.(4)The correlation between the deformation of the surrounding rock and the change of anchor rod/anchor cable axial force in the field was analysed,and the stress state of anchor rod/anchor cable in different service periods of the roadway was proposed and applied to the evaluation of the stability of the 312 retracement roadway in Ji’nan coal mine.There are 75 drawings,36 tables and 90 references in this thesis. |
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