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. 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 P0 and the others smaller than P0 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.
The constant-resistance-large-deformation (CRLD) bolt developed by academician Manchao He has been widely used in engineering due to its extraordinary mechanical properties [1–3]. The constant-resistance-large-deformation (CRLD) bolt is also called "NPR bolt" due to its superb Mechanical Properties from its internal negative Poisson's ration structure [4,5]. In the coming decades, deep mining and high slope mining of open pit mines will be the main forms of mineral resource mining in China . The dynamic disaster (rock burst) will be one of the main challenges in mining rock mechanics . Therefore, it is of great significance to study the dynamic response of NPR bolt.
In order to further understand the dynamic response of NPR bolt, SHTB (split Hopkinson tensile bar) tension test was carried out by Manchao He to study the dynamic behavior of NPR bolt under high speed impact load [8,9]. Weight dropping test is widely used to study the dynamic behavior of materials and structures under low-speed impact loads with strain rates ranging from 10−1s−1 to 102s−1.