scholarly journals Reproduction Method of Rockfall Geologic Hazards Based on Oblique Photography and Three-Dimensional Discontinuous Deformation Analysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Xiaodong Fu ◽  
Haifeng Ding ◽  
Qian Sheng ◽  
Jian Chen ◽  
He Chen ◽  
...  
Keyword(s):  
Geometric Characteristic ◽  
Three Dimensional ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Geologic Hazard ◽  
Block System ◽  
Geologic Hazards ◽  
Discontinuous Deformation ◽  
Reproduction Method ◽  
Dda Method

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.

A Three-Dimensional Discontinuous Deformation Analysis Method for Investigating the Effect of Slope Geometrical Characteristics on Rockfall Behaviors

2019 ◽  
Vol 16 (08) ◽  
pp. 1850122 ◽  
Author(s):  
Guoyang Liu ◽  
Junjie Li
Keyword(s):  
Slope Angle ◽  
Three Dimensional ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Motion Trajectories ◽  
Geometrical Characteristics ◽  
Damage Degree ◽  
Slope Excavation ◽  
Discontinuous Deformation ◽  
Dda Method

In the present study, a three-dimensional discontinuous deformation analysis (3D DDA) method was developed and used to investigate the effect of slope geometrical characteristics on rockfall behaviors. The slope geometrical characteristics of rockfall, such as the slope height, slope angle and slope shape, were summarized, and the corresponding calculation models were proposed. The algebraic computation and contact mechanics of the three-dimensional (3D) global contact theory were illustrated and implemented into the 3D DDA method. The accuracy of the developed 3D DDA method was verified through the four basic movement forms of rockfall: freefalling (oblique projectile), sliding, rolling and bouncing. Numerical examples were performed to study rockfall behaviors under different slope geometrical characteristics by analyzing the kinetic energy or velocity conversion, motion trajectories, and damage degree and range of moving blocks. The results demonstrate that the 3D DDA method can accurately simulate rockfall movement, which is significantly affected by slope geometrical characteristics. Furthermore, some suggestions for slope excavation and protection were put forward.

Research on the Effect of Tree Barriers on Rockfall Using a Three-Dimensional Discontinuous Deformation Analysis Method

2019 ◽  
Vol 17 (08) ◽  
pp. 1950046
Author(s):  
Guoyang Liu ◽  
Junjie Li
Keyword(s):  
Three Dimensional ◽  
Protective Role ◽  
Discontinuous Deformation Analysis ◽  
Impact Factors ◽  
Deformation Analysis ◽  
Barrier Effect ◽  
Motion Trajectories ◽  
Discontinuous Deformation ◽  
The Impact ◽  
Dda Method

On rockfall slopes, trees can play a natural and efficient protective role in preventing the occurrence of rockfall disasters. This paper presents a study on the tree barrier effect on rockfall based on a three-dimensional discontinuous deformation analysis (3D DDA) method. The tree barrier effect on rockfall is studied considering the 3D spatial effect of rockfall movement and the 3D spatial distribution of trees. The basic movement forms and collision modes of rockfall related to the tree barrier are classified, and the impact factors of tree arrangements on rockfall are proposed. The contact mechanism employed in the 3D DDA method is illustrated, and the accuracy of the 3D DDA rockfall simulation is verified by comparing with the results obtained from laboratory experiments. Numerical examples are conducted to study the effect of the tree barrier on rockfall, and general laws are derived by analyzing the variation of kinetic energies and motion trajectories of moving blocks. The results show that the 3D DDA method can effectively predict the 3D motion behaviors of rockfall and assess the tree barrier effect. Furthermore, a reasonable arrangement of trees or a combination of protective facilities and trees can prevent or mitigate the rockfall hazards.

DEVELOPMENT OF 3D NUMERICAL MANIFOLD METHOD

2010 ◽  
Vol 07 (01) ◽  
pp. 107-129 ◽  
Author(s):  
LEI HE ◽  
GUOWEI MA
Keyword(s):  
Virtual Work ◽  
Three Dimensional ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Numerical Manifold Method ◽  
Block System ◽  
Structure Description ◽  
Operation Rule ◽  
Discontinuous Deformation ◽  
Numerical Manifold

The numerical manifold method (NMM) is a combination of the finite element method (FEM) and discontinuous deformation analysis (DDA) method. It provides a robust numerical solution to a solid medium with dense discontinuities. This paper extends NMM to the three-dimensional domain based on the 2D fundamentals. The general framework of the 3D NMM is introduced, including the cover geometry patterns (GP) with division structure from hexahedron to tetrahedron, and general formulations based on the virtual work principle. The block cutting process to generate discrete blocks are discussed through the topological structure description of blocks, and the operation rule of blocks is explained. The proposed 3D block generation algorithm allows for any arbitrary discrete structure or block system. Three numerical examples are presented to demonstrate that the developed 3D numerical manifold code is effective and applicable to 3D continuum solids. Further developments aim to incorporate contact models to simulate complicated discrete block system.

scholarly journals Numerical modeling of complex hydraulic fracture networks based on the discontinuous deformation analysis (DDA) method

2021 ◽  
pp. 014459872098153
Author(s):  
Yanzhi Hu ◽  
Xiao Li ◽  
Zhaobin Zhang ◽  
Jianming He ◽  
Guanfang Li
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Fracture Network ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Fracture Networks ◽  
Proposed Model ◽  
Discontinuous Deformation ◽  
Shale Reservoirs ◽  
Dda Method

Hydraulic fracturing is one of the most important technologies for shale gas production. Complex hydraulic fracture networks can be stimulated in shale reservoirs due to the existence of numerous natural fractures. The prediction of the complex fracture network remains a difficult and challenging problem. This paper presents a fully coupled hydromechanical model for complex hydraulic fracture network propagation based on the discontinuous deformation analysis (DDA) method. In the proposed model, the fracture propagation and rock mass deformation are simulated under the framework of DDA, and the fluid flow within fractures is simulated using lubrication theory. In particular, the natural fracture network is considered by using the discrete fracture network (DFN) model. The proposed model is widely verified against several analytical and experimental results. All the numerical results show good agreement. Then, this model is applied to field-scale modeling of hydraulic fracturing in naturally fractured shale reservoirs. The simulation results show that the proposed model can capture the evolution process of complex hydraulic fracture networks. This work offers a feasible numerical tool for investigating hydraulic fracturing processes, which may be useful for optimizing the fracturing design of shale gas reservoirs.

Sign in / Sign up

Export Citation Format

Share Document