Abstract:
Rockfall ditches or catchment areas aim to collect falling blocks at the toe of a source zone by dissipating the
energy of blocks in an excavated trench. The effectiveness of a rockfall ditch is simply expressed by its block
catchment performance and can be evaluated by empirically using existing design charts as well as rockfall
simulations. Although 2-dimensional (2-D) analysis has been executed to assess the catchment ditch effectiveness
in engineering practice, 3-dimensional (3-D) rockfall models have not received enough attention so far. In this
study, the effectiveness of a considerably long rockfall ditch to protect a settlement from falling rocks was
assessed on the basis of 3-D rockfall analyses executed using high-resolution digital surface models. The rockfall
ditch efficiency was found to be moderate to limited for various segments considering the percentage of blocks
not trapped by the ditch. Moreover, the sensitivity of ditch efficiency to ditch depth was analyzed by automated
image processing method as well. Additionally, a particular section of ditch alignment was fictitiously excavated
or filled by synthetic Digital Surface Model (DSM) generation through image processing. 3-D rockfall modeling
carried out using the DSMs with synthetically manipulated ditches points out that the effectiveness of a catch ment ditch is highly depended upon ditch depth. Even a small volume of block accumulation inside the ditch
definitely reduces the ditch performance resulting extended runout distances reaching to residential area.
Finally, 3-D rockfall modeling is accepted to be an effective tool to rate the efficiency of existing rockfall ditches
and synthetically generated ditches on DSMs (or DEMs) by means of automated image processing method may
assist the control of current ditch dimension as well as new catchment ditch design.
