Abstract
Rockfall geologic hazards are widely distributed. Due to their concealed nature, rockfalls are difficult to investigate using traditional contact survey methods, and the hazards they pose affect major projects and people’s safety. Reproducing methods, including scene survey and movement process analysis, are primary tasks used to prevent these hazards; however, few reconstruction methods can directly apply the parameters of the rockfall geologic hazards obtained by the scene survey to evaluate the movement process. To address this problem, a method of reproduction based on oblique photography and three-dimensional discontinuous deformation analysis (3D-DDA) is proposed; the method consists of three key techniques (oblique photography, 3D rock block system modeling, and 3D rock block system analysis). First, geometric characteristic parameters of the terrain, rockfall, and discontinuities are extracted based on oblique photography using an unmanned aerial vehicle (UAV). Second, the block system model of rockfall is reconstructed by using 3D computational geometry theory and taking these geometric characteristic parameters as an input. Finally, the whole evolution process of rockfall geologic hazard, including initiation, movement, and accumulation, is simulated by the 3D-DDA method. To verify the practicability of this reproduction method, a typical rockfall geologic hazard, located in the K8 + 050 section of the Gaohai expressway, Yunnan, China, is studied. In addition, the characteristics of 19 dangerous rock masses in the survey area are clarified, and the geometric features of the discontinuities in the rock masses are extracted based on oblique photography using an UAV. The block system model of a potential rockfall is reconstructed, the movement trajectory is simulated by the 3D-DDA method, and the evolution process of velocity and kinetic energy of the rockfall verifies that the spatial layout of the current three-level passive protective nets system is reasonable. The case study indicates that the proposed method provides a geological and mechanical model for the risk assessment of rockfall geologic hazards.
Highlights
After complex geological processes, geological discontinuities with different sizes and properties, such as faults, joints, and fissures, are widely distributed in rock masses
Using the 3D-discontinuous deformation analysis (DDA) codes developed by Shi (2001), much research into the movement and underlying mechanisms of rockfall geologic hazards has been carried out (Yang et al, 2004; Chen et al, 2013; Zheng et al, 2014; Wang et al, 2017; Liu et al, 2019). These results show that the 3D-DDA method can simulate the free falling, sliding, rolling, and rebound of rockfall, and the spatial effect of the interaction between a rockfall and the slope surface
A method of reproduction based on oblique photography and 3D-DDA is demonstrated
Summary
Geological discontinuities with different sizes and properties, such as faults, joints, and fissures, are widely distributed in rock masses. Scholars have carried out much research into two important aspects of reconstruction of rockfall geologic hazards; few methods of reconstruction can directly apply the parameters of the rockfall geologic hazards obtained by a scene survey to assess the movement process (Lan et al, 2010), which restricts the development of prevention techniques against such hazards. To address this problem, a method of reproduction based on oblique photography and 3D-DDA is demonstrated. A Brief of the Reproduction Method presents a brief of the reproduction method; Background of a Rockfall Geologic Hazard Case introduces a case of rockfall geologic hazard; in Basic Data Extracted Using Oblique Photography, 3D Rock Block System Modeling, and Movement Process Analysis of the Rockfall Geologic Hazard, three key techniques used in the reproduction method, including oblique photography, 3D rock block system modeling, and 3D rock block system analysis, are described and verified by the way of a case study
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