A study of parameters used in boulder survey

Abstract

Boulderfall regularly occurs in the natural terrain in Hong Kong. In order to assess the stability and the potential hazard of boulders in the hillside, boulder survey is typically employed and the work is carried out by geologists. However, the available guideline in boulder survey is not explicit enough for performing reliable surveys. The correlation between different boulder survey parameters is poorly established. This project intends to correlate between different parameters, in particular, the shape and angularity of the boulders and the movement mechanism during their travels downslope. In the present study, nine 3D printed boulder blocks of different shapes and three marble slope platforms of varying waviness were used to study different parameters used in boulder survey. The motion of the blocks was recorded by a high speed camera and analyzed with 2D motion analysis software. The results showed that specimens with different shapes and angularities behaved differently when travelling on the slope. It was concluded that the shape and the angularity of the blocks were the key factors in controlling the main movement mechanism of the blocks, while the slope waviness was found to influence the subsidiary movement mechanism in addition to the main mechanism. The established correlation provided a reference for the practitioners in boulder survey to determine the potential movement mechanisms for boulders with certain shapes and angularities. The slope waviness also revealed the influence of the changes in velocities and kinetic energies of the block along the slope.