Zhongguo dizhi zaihai yu fangzhi xuebao (Apr 2022)
Experiment on the effect of forward and reverse rotation speeds of rockfall on normal restitution coefficient
Abstract
In order to explore the effect of forward and reverse rotation speeds of rockfall on normal restitution coefficient (Rn), three typical blocks of cube, disc and cylinder were customized, and the impact tests of each block with slope at different forward and reverse rotation speeds in X and Y axes were carried out through the specially developed rockfall impact test device. Results show that the rotation speed has no effect on Rn when the disc and the cylinder shaped blocks rotate around the Y-axis (approximately normal impact); when the three shaped blocks rotate along the X-axis (non-normal impact), there exists a certain correlation between the rotation speed and Rn, but Rn is also affected by the block shape and impact posture. Thus, a comprehensive variable - impact posture coefficient (IPC) was introduced to quantify the effect of rotation speed on Rn. In view of the difference of the mechanical action mechanism of normal impact force on Rn under different impact posture, the impact-rebound characteristics of the blocks were classified and discussed. For the type of rebounding after only one impact, IPC and Rn have linear positive correlation and negative correlation respectively when the mass center (C) is behind and in front of the contact point (CP) in the forward rotation test, and the results of the reverse rotation test were just the opposite. For the type of rebounding after two impacts, regardless of forward or reverse, whether C is behind or in front of CP during the first impact, Rn and IPC of each shaped block are strongly positive correlation, yet the relevant laws are not consistent under various working conditions. These conclusions basically reveal the influence of rotation speed on Rn, and provide a reference for accurate prediction of impact-rebound process of rotating irregular rockfall.
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