Experiment Research On Stress Wave Nondestructive Testing Technology For Bolt Anchorage Quality

At present, the methods of testing technology for bolt anchoring quality commonly used in geotechnical engineering field are mostly destructive, which can destroy the internal structure of rock bolts system, thus, the demand for seeking a reliable, rapid, economic and nondestructive testing method for bolt anchoring quality is becoming increasingly urgent.This paper conducts a theoretical study on the propagation law of stress waves in elastic rods and the propagation law of elastic rods under different constraints. Through laboratory simulation experiments, this author verifies the propagation theory of the stress wave; Through contrasting spot tests for rock bolts in coal mine with the laboratory simulation experiments, so as to verify the feasibility of the stress wave nondestructive testing technology for bolt anchoring quality. The research works this author carries out are as follows:1. Firstly, the author introduces the bolt support theory, studies the propagation law of stress waves in the anchor system, the energy attenuation and distribution of the stress wave in rock bolts system, thereby providing theoretical basis for the stress wave nondestructive testing technology for bolt anchoring quality.2. These indexes (including effective development length, attenuation coefficient, amplitude ratio, frequency ratio, dynamic stiffness and fundamental frequency) can evaluate the fulu of bolt anchoring quality. Experimental results show that the concretion wave speed size reflects the cohesive strength of rock bolt and anchoring medium, the concretion wave speed can reflect the anchoring quality of rock bolt from the other aspects.3. By simulation experiment in laboratory, the author studies the wave velocity of stress wave in the free segment of rock bolt and in the anchoring segment. The author conducts time-domain analysis on test signal, so as to show that the wave velocity in the free segment of rock bolt doesn’t vary with the change of the load on the rock bolt. The concretion wave speed tends to increase with the increase of the load on the rock bolt. Through conducting frequency-domain analysis on test signal, so as to find out the fundamental frequency of the test signal under different loads, using ORIGIN software to fit the load-fundamental frequency function, the author finds that it really presents three times a power function relation.4. Using the stress wave nondestructive testing method for bolt anchoring quality, the author detects the rock bolt in71312roadway in GuoYang2# Mine and evaluates the quality of bolt anchoring, verifing the feasibility of the stress wave nondestructive testing technology for bolt anchoring quality.