The effect of surface irregularities on a falling rock motion

ABSTRACT

This laboratory study seeks to investigate the effect of surface irregularities on the motion characteristics of a falling rock. The irregularly-shaped surfaces of greywacke with a range of joint roughness coefficient (JRC) from 2 to 18 were used in an experimental setup where a falling rock was dropped from a height of 110 cm. A high-speed camera was utilised to capture the trajectory of the falling rock upon its impact with the rock surface. The data from 287 tests were statistically analysed to determine the dominant type of motion and to establish relationships between JRC and the coefficient of restitution (CoR). The effect of surface roughness was seen in different modes of motion of the falling rock with more irregular surfaces often produced ‘sliding’ or ‘rolling’ instead of ‘bouncing’. The obtained data indicated that the rock surface roughness did not seem to have a significant effect on CoR; however, it affected the rebound angle of the falling rock.

KEYWORDS:

• Laboratory test
• coefficient of restitution
• joint roughness coefficient
• rebound angle

Acknowledgements

The authors would like to acknowledge Mr Thomas Cogan for his invaluable help with laboratory testing. This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sctors.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sctors.