Rolling motion behavior of rockfall on gentle slope: an experimental approach

The effects of slope surface material, slope gradient, block shape, and block mass conditions on rockfall rolling velocity were estimated with orthogonal test approach. Visual analysis shows that the importance of the factors is slope surface material > slope gradient > block shape > block mass. All the factors except block mass have the F value greater than the critical value, suggesting that these three factors are the key factors affecting the rockfall rolling velocity. Factor interaction analysis shows that the effect of the slope gradient relies largely on the slope surface conditions, and the block shape has little influence if the slope gradient is larger than a critical value. An empirical model considering the three key factors is proposed to estimate the rolling velocity, of which the error is limited to 5% of the testing value. This model is validated by 73 field tests, and the prediction shows excellent correlation with the site test. Thus, this analysis can be used as a tool in the rockfall behavior analysis.