Dynamic characteristics of constant-resistance-large-deformation bolts based on weight-dropping tests
GONG Weili1，2，SUN Yaxing1，2，GAO Xia1，2，HE Manchao1，2，QI Peng1，2
(1. State Key Laboratory for Geomechanics and Deep Underground Engineering，China University of Mining and Technology，Beijing 100083，China；2. School of Mechanics and Civil Engineering，China University of Mining and Technology，
Beijing 100083，China)
Abstract：In order to optimize the rock support design under the dynamic loading conditions such as rock bursts or coal bumps，weight-dropping tests were carried out to two samples of the constant-resistance-large-deformation (CRLD) bolts which have widely been used as the rock support in longwall mining based on gob-side entry retaining without coal pillar(110 mining method). Analytical models including the critical impact height，impact working resistance and displacement for the CRLD bolts were established based on the stress wave and elastic dynamics theories. The weight-dropping tests under different dropping heights on the bolt samples were conducted. The entire time curve for the impact working resistance under single impact has multiple peaks with the first peak larger than the static working resistance and the others smaller than and damped to zero due to the unloading waves created by the transmitting and reflecting waves along the bolt. Waveform analysis on the first peak in the enlarged time sale revealed the load-damping modes for the CRLD bolt under impact loading，i.e. the first phase is the multi-periodical oscillations with the decreased magnitude of the impact force and the second phase is the fast-damped frictional sliding motions. The theoretically predicted results have a good agreement with the testing data.
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2018, Vol. 37 
