Simulation and Statistical Analysis of Motion Behavior of a Single Rockfall

The impact force of a rockfall is mainly determined by its moving behavior and velocity, which are contingent on the rock shape, slope gradient, height, and surface roughness of the moving path. It is essential to precisely calculate the moving path of the rockfall in order to effectively minimize and prevent damages caused by the rockfall. By applying the Colorado Rockfall Simulation Program (CRSP) program as the analysis tool, this research studies the influence of three shapes of rock (spherical, cylindrical and discoidal) and surface roughness on the moving path of a single rockfall. As revealed in the analysis, in addition to the slope gradient, the geometry of the falling rock and joint roughness coefficient ( JRC ) of the slope are the main factors affecting the moving behavior of a rockfall. On a single flat slope, both the rock-s bounce height and moving velocity increase as the surface gradient increases, with a critical gradient value of 1:m = 1 . Bouncing behavior and faster moving velocity occur more easily when the rock geometry is more oval. A flat piece tends to cause sliding behavior and is easily influenced by the change of surface undulation. When JRC <1.4 the moving velocity decreases and the bounce height increases as JRC increases. If the gradient is fixed, when JRC is greater, the bounce height will be higher, while the moving velocity will experience a downward trend. Therefore, the best protecting point and facilities can be chosen if the moving paths of rockfalls are precisely estimated.

Authors:

• Iau-Teh Wang
• Chin-Yu Lee

Keywords:

• rock shape
• surface roughness
• moving path.

References:

[1] Y. Hong, and R. F. Adler, "Predicting global landslide spatiotemporal
distribution: Integrating landslide susceptibility zoning techniques and
real-time satellite rainfall estimates," International Journal of Sediment
Research, vol. 23, no. 3, pp. 249-257, 2008.
[2] G. P. Giani, "Rock Slope Stability Analysis," Balkema, Rotterdam,
1992, pp. 361.
[3] T. J. Pfeiffer, and T. D. Bowen, "Computer simulation of rockfalls,"
Bulletin of the Association of Engineering Geologist, vol. 26, pp.
135-146, 1989.
[4] T. J. Pfeiffer, J. D. Higgin, and R. D. Andrew, "Colorado Rockfall
Simulation Program," User Manual for Version 2.1- Colorado School of
Mines, Golden, CO, 1991.
[5] S. S. Wu, "Rockfall evaluation by computer simulation," Transportation
Research Record 1031, TBR, National Research Council. Washington
D. C., pp. 1-5. 1984.
[6] A. M. Ritchie, "The evaluation of rockfall and its control," Highway
Research Record, no. 17, Washington D.C., pp. 1-5, 1963.
[7] H. Wadell, "Volumn shape and roughness of rock particles," Journal of
Geology, vol. 40, pp. 443-451, 1932.
[8] A. Azzoni, L.G. Barbera, and A. Zaninetti, "Analysis and prediction of
rockfalls using a mathematical model," International Journal of Rock
Mechanics and Mining Science, Geomechanics Abstracts, vol. 32, no. 7,
pp. 709-724, 1995.
[9] A. Azzoni, and M. H. Freitas, "Experimentally gained parameters,
decisive for rockfall analysis," Rock Mech. and Rock Engrg, vol. 28, no.
2, pp. 111-124, 1995.
[10] Y. Okura, H. Kitahara, T. Sammori, and A. Kawanami, "The effects of
rockfall volume on runout distance," Engineering Geology, vol. 58, pp.
109-124, 2000.
[11] P. G. Fookes, and M. Sweeney, "Stabilization and control of local rock
falls and degrading rock slope," Quarterly J. Engrg. Geology, vol. 9, pp.
37-55, 1976.
[12] I. Statham, "A simple dynamic model of rockfall: some theoretical
principles and field experiments," International Colloquium on Physical
and Geomechanical Models, pp. 237-258, 1979.
[13] D. Bozzolo, and R. Pamini, "Simulation of rock falls down a valley
side," Acta Mechanica, vol. 63, pp. 113-130, 1986.
[14] P. Paronuzzi, "Probabilistic approach for design optimization of rockfall
protective barriers," Quarterly J. Engrg. Geology, vol. 22, pp. 135-146,
1989.
[15] S. G. Evans, and O. Hungr, "The assessment of rockfall hazard at the
base of talus slopes," Canadian Geotechnical Journal, vol. 30, pp.
630-636, 1993.
[16] J. M. Gere, and S. P. Timoshenko, "Mechanics of Materials, Second
Edition, Appendix E, 1980, pp. 1-54.
[17] N. Barton, and V. Choubey, "The shear strength of rock joints in theory
and practice," Rock Mechanics, vol. 10, pp. 1-54, 1977.