Half-scale experimental study of rockfall impacts on sandy slopes

Abstract. In the framework of rockfall trajectory modelling, the bouncing phenomenon occurring when a rock block impacts with the slope surface is the most difficult to predict, owing to its complexity and its very limited understanding. To date, the rebound is commonly quantified by means of two coefficients of restitution estimated from a rough description of the ground material. To acquire a better knowledge of the bouncing phenomenon and to investigate the influence of various impact parameters, a comprehensive experimental study was undertaken at the LMR-EPFL (Rock Mechanics Laboratory – Swiss Federal Institute of Technology Lausanne). After a summary of the main conclusions drawn from a small-scale study, the paper focuses on half-scale experiments, describing first the testing device and the data processing and analysing then the influence of several impact parameters. It is observed that the rebound and the commonly-used coefficients of restitution expressed for the mass centre of the block depend not only on slope material characteristics, but also on factors related to the kinematics (slope inclination and impact velocity) and to the block (weight, size and shape). As many trajectory computer codes consider constant coefficients of restitution only function of the outcropping material, the trajectory results should be interpreted with caution and always checked against field observations.

[1]  A. Azzoni,et al.  Experimentally gained parameters, decisive for rock fall analysis , 1995 .

[2]  Warren Douglas Stevens,et al.  ROCFALL: A TOOL FOR PROBABILISTIC ANALYSIS, DESIGN OF REMEDIAL MEASURES AND PREDICTION OF ROCKFALLS , 1998 .

[3]  B. Heidenreich.  Small- and half-scale experimental studies of rockfall impacts on sandy slopes , 2004 .

[4]  J. Falcetta.  UN NOUVEAU MODELE DE CALCUL DE TRAJECTOIRES DE BLOCS ROCHEUX , 1985 .

[5]  Kt Chau,et al.  The coefficient of restitution for boulders falling onto soil slopes with various values of dry density and water content , 2021, Slope Stability Engineering.

[6]  C. F. Lee,et al.  Shape effects on the coefficient of restitution during rockfall impacts , 1999 .

[7]  J. J. Wu,et al.  Coefficient of restitution and rotational motions of rockfall impacts , 2002 .

[8]  F. Berger,et al.  Real-size experiments and 3-D simulation of rockfall on forested and non-forested slopes , 2006 .

[9]  D. Peila,et al.  Block falls on rock slopes. Application of a numerical simulation program to some real cases , 1990 .

[10]  Sara Montani Stoffel.  Sollicitation dynamique de la couverture des galeries de protection lors de chutes de blocs , 1998 .

[11]  R. Wong,et al.  Shape and Mechanical Properties of Slope Material Effects on the Coefficient of Restitution of Rockfall Study , 2000 .

[12]  G. Giani.  Rock Slope Stability Analysis , 1992 .

[13]  N. H. Macmillan,et al.  Further studies of the oblique impact of a hard sphere against a ductile solid , 1981 .

[14]  C Azimi,et al.  METHODE DE CALCUL DE LA DYNAMIQUE DES CHUTES DE BLOCS - APPLICATION A L'ETUDE DU VERSANT DE LA MONTAGNE DE LA PALE (VERCORS) , 1982 .

[15]  V. Labiouse,et al.  Experimental study of rock sheds impacted by rock blocks , 1996 .

[16]  V. Labiouse.  Fragmental rockfall paths : comparison of simulations on alpine sites and experimental investigation of boulder impacts , 2004 .

[17]  T. Pfeiffer,et al.  Computer Simulation of Rockfalls , 1989 .

[18]  Shie-Shin Wu,et al.  ROCKFALL EVALUATION BY COMPUTER SIMULATION , 1985 .

[19]  D. Bozzolo,et al.  Simulation of rock falls down a valley side , 1986 .