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Rock and Soil Mechanics

Abstract

To study the dynamic response characteristics of host rockmass and supporting bolt under blasting load, a three-dimensional dynamic loading physical model test was performed using an underground engineering model test system. The propagation law of blasting seismic wave and the dynamic response characteristics of supporting bolt were tested using electric spark source instead of traditional explosives. Experimental research results show that the electric spark source has the characteristic of the impact loading, which can well replace traditional high explosives. The radial acceleration peak values and the axial and hoop strain peak values of blasting seismic wave within host rock do not decrease gradually as the increasing of the radial distance along the excavation, but show a wave-like attenuation pattern of positive and negative alternating. In addition, the acceleration peak values show a nonlinear and decrease gradually along the excavation axial direction. The peak acceleration values are affected largely by the seismic load amplitude, that is, the higher the source load, the higher the peak acceleration value at the same measurement point. In addition, the vibration characteristics of the supporting bolt were measured under blasting load. It is found that the extension anchor bolt, the free section of the anchor bolt is mainly in tension state, but the anchor section of the bolt is in the state of both tension and compression. The maximum tensile strain of the anchor and free section is approximately the same, while the maximum compressive strain of the anchor section is much larger than that of the free section. The vibration duration of anchor section and free section is also approximately similar. As for the full-anchored bolt, the bolt has subjected both a tensile state and a compressive state, and the tensile strain is greater than the compressive strain. As for the end-anchored bolt, the stress state is mainly in the tension state, and the tensile strain is much greater than the compressive strain. The research conclusion not only has important theoretical significance, but also can provide predictable guidance for the ground support design of underground excavation.

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