The paper presents the statical research tests of rod bolt made of plastic with a length of 5.5 m, which were performed in a modern laboratory test facility at the Department of Underground Mining of the University of Science and Technology. Innovative The Self-excited Acoustic System (SAS) used to measure stress changes in the bolt support was characterized. The system can be used for the non-destructive evaluation of the strain of the bolt around the excavations as well as in tunnels. The aim of the study was to compare the re-sults recorded by two different measuring systems, thanks to which it will be possible to assess the load of long bolt support by means of the non-destructive method. The speed and simplicity of measurement, access to the sensors, accuracy of measurement and reading should be kept in mind in determining the load of rock bolt support . In addition, the possibility of damage to the sensor as a re-sult of technological or natural hazards should also be taken into account. In economic conditions, the „technical - balance laws of production”, which ex-cludes the use of load sensors on each bolt must be preserved. The use of indi-vidual load sensors of rock bolt support for the boundary state, allows appro-priate protection actions of the mining crew against sudden loss of excavation stability to be taken. The paper presents two basic effects used in the ultrasonic measurement sys-tem. The first result was the existence of stable limit cycle oscillations for posi-tive feedback. This effect is called the self-excited effect. The second effect is called the elasto-acoustic effect. It means that with the change of elastic stress-es in the material bring the change of the speed of propagation of the wave. In this connection, the propagation time between measuring heads is also changed. This effect manifests itself in the change in the oscillation frequency of the self-excited system. For this reason, by measuring the frequency of self-excited oscillation, it is possible to indirectly determine the level of effort of the tested material.

Monitoring the stress change of bolt and knowing the anchoring condition in a reasonable and effective way, accurately, can effectively prevent tunnel accident from breaking out. The stress of rock mass around the roadway is usually transferred to the anchor rod in the form of axial load, so it is of great significance to study the axial load of the bolt. In this paper, a full size anchoring and drawing experiment system was designed and established, innovatively, which realized the pull-out test of 2.5 m prestressed end Anchorage and the full-length Anchorage by using the new resin anchorage agent under vertical and horizontal loads. Through the application of fiber Bragg grating (FBG) sensing technology to the test of full-scale anchor rod, the axial force distribution characteristics of the end Anchorage and the full-length Anchorage anchor rod were obtained under the action of pre-tightening torque and confining rock pressure. The comparison indicates that the proportion of high stress range accounts for only 17.5% and the main bearing range is near the thread end of anchor rod, the proportion of main bearing range of end Anchorage is 83.3%, and the feasibility of FBG force-measuring anchor rod is verified in the field. The research results have certain reference value.

The stress field of the roadway under multi-seam mining is complex due to multiple mining disturbances. The bolting control of the roadway under multi-seam mining has attracted wide concern. Moreover, conventional metal supporting materials in the coal rib are prone to sparks when shearer works, and new bolting materials are urgently needed. Taking a track roadway under multi-seam mining in China as the engineering case, the mining-induced stress field of the track roadway under multi-seam mining was investigated through numerical simulation and lab and field tests. The test evaluated the mechanical behaviour of FRP bolts and rebar bolts, as well as their anchorage performance under different conditions. Comparative analysis was conducted on the deformation and failure characteristics of the roadway under different bolting parameters to determine an optimised bolting scheme for the track roadway in the I011501 working face. The results show that the goafs and the remaining coal pillars in the overlying coal seams increase the stress in the track roadway in the I011501 working face, especially for the lower rib and roof. The tensile force of the 27 mm-diameter FRP bolt is 1.2 times that of the 22 mm-diameter rebar bolt. The shear strength of the full-length anchored FRP bolt is 70.8% higher than that of the end-anchored bolt. The peak stress of the full-length-anchored bolt is in the shallow coal and rock mass. The optimised bolting scheme of the track roadway subject to multi-seam mining is determined, and the cost of the optimised bolting scheme is lower by about 25.2%, as compared with the primary bolting scheme. Numerical simulation and field application results indicate that the optimised bolting scheme can significantly reduce the deformation and plastic failure of the track roadway in the I011501 working face, which is under multi-seam mining conditions.