Abstract
Coefficient of restitution is regarded as a dominating parameter in rockfall research. Generally, small-scale experiments were developed without considering interactions between boulder and slope. However, preimpact moving statuses are essential to evaluate rockfall behaviors. To reveal the effect of preimpact interactions on coefficient of restitution, energy dissipation considering initial velocity, surface type, and slope angle is executed based on medium-scale tests. The results show that (1) as the inclination of initial velocity, higher rebound height, and the declining normal coefficient of restitution occur, a determinable linear function could demonstrate relationships among energy dissipation and all coefficient of restitution; when initial velocity exceeds 5 m/s, the recovery ability shows and produces an increasing trend with respect to the variation of kinematic coefficient of restitution and kinetic energy coefficient of restitution. (2) As the surface material varies, slope hardness and rebound ability influence normal coefficient of restitution, and the surface roughness and rotation feature dominate tangential coefficient of restitution; considering preimpact slope and boulder interactions, four types of coefficient of restitution follow declining trend with different material sequence. (3) Slope angle affects normal coefficient of restitution, and tangential coefficient of restitution relatively descends 18% and inclines 10% when the angle ranges from 30° to 75°; regarding preimpact moving status, it differs from bounce times. The correlation between preimpact energy dissipation and four coefficients of restitution can be represented by the same decreasing linear function, when increasing the slope angle.
Highlights
(3) Slope angle affects normal coefficient of restitution, and tangential coefficient of restitution relatively descends 18% and inclines 10% when the angle ranges from 30° to 75°; regarding preimpact moving status, it differs from bounce times. e correlation between preimpact energy dissipation and four coefficients of restitution can be represented by the same decreasing linear function, when increasing the slope angle
Physical features of slope angle and surface type are applied, while the kinetic features of boulder initial velocity are discussed. ese features are not well-documented regarding the preimpact interaction effect according to the previous study. erefore, a special designed rockfall modeling system is adopted in this paper. e major critical factors are evaluated and analyzed according to the moving variation and energy dissipation
Energy dissipation divergences in terms of initial velocity, surface type, and slope angle parameters at the slope interval are considered. e correlations between the slope arousing effect and energy dissipation are developed. e energy dissipation displayed as the ratio of the test acquired kinetic energy and the calculated kinetic energy. e formula is ξtransit where ξtransit is the energy dissipation coefficient, Em is developed based on the test measured velocity according to kinetic energy theorem, and Ec is obtained based on energy conservation law without considering the impact loss between rock and slope. e kinetic energy is calculated by using the sum of initial kinetic energy and gravitational energy
Summary
Rockfall has always been considered as a random and frequent occurring natural disaster aroused by human activity or weathering influence (erosion, saturation, earthquake, rainfall, and freezing) with no objection [1,2,3]. E research of rockfall states that the characteristics of moving status after impact are influenced by slope properties, and by other key parameters correlating to the boulder. Prior tests are carried on small or medium scale, where the efforts are not focused on the preimpact status of the boulder and would not reflect the truly influence on COR and impact energy. It only deals with the temporary moment just before and after the impact, which may ignore the comprehensive function of the preinteractions between the slope and boulder. Physical features of slope angle and surface type are applied, while the kinetic features of boulder initial velocity are discussed. ese features are not well-documented regarding the preimpact interaction effect according to the previous study. erefore, a special designed rockfall modeling system is adopted in this paper. e major critical factors are evaluated and analyzed according to the moving variation and energy dissipation
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