Dynamic analysis of resin-grouted roof bolt

The widespread preference for rock bolts in providing adequate rock stability in underground mines and man-made cavities makes it necessary to obtain a better understanding of the response of such structures when subjected to intermittent shocks such as those from blasting. Although it is widely accepted that fully resin-grouted rock bolts provide better roof stability in the areas of very poor roof conditions, there is little knowledge of their in situ response due to seismic shocks generated by blasting. Consequently, the design of optimum bolt patterns and evaluation of their effectiveness are difficult.;The objective of this study is to evaluate the dynamic response of a resin grouted bolt during blasting and study the relationship between roof bolts strains and the vibrations of the bolt. Establishing these relationships would prove very useful in describing the transfer of stresses to the roof bolting system during blasting, and greatly facilitate the development of the optimum bolting requirements.;An instrumentation system used to record blast induced roof vibration and roof bolt's response was developed. A complete data processing system was assembled for analyzing the recorded strain and acceleration signals. Three field experiments were conducted in the MTU Experimental Mine. Dynamic strain signals on roof bolt and acceleration signals on roof and bolthead were successfully measured in these field experiments.;A time series analysis technique was used to decompose the strain and acceleration signal of the roof bolt and rock mass respectively. The components of axial and bending vibrations of the bolt were identified. Their distributions with distance into the roof rock were found in both time and frequency domains. The transfer of energy from rock to the roof bolt was determined by frequency response functions. Dominant frequencies of the frequency response function. FRF coincided with those from strains on roof bolt. The analysis technique permitted the identification of the resin-grouted roof bolt's modal parameters. To obtain a physical insight into the dynamics of roof bolt system, a finite element method was applied to idealized approximate models of roof bolting system. The experimental results and theoretical calculation from simplified models with finite element method were compared.