scholarly journals Efficient Investigation of Rock Crack Propagation and Fracture Behaviors during Impact Fragmentation in Rockfalls Using Parallel DDA

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Lu Zheng ◽  
Yihan Wu ◽  
Wei Wu ◽  
Hong Zhang ◽  
Xinyan Peng ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Impact Velocity ◽  
Rock Fracture ◽  
Slope Angle ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Impact Fragmentation ◽  
Fracture Behaviors ◽  
Virtual Joints ◽  
The Impact

The study of the rock crack propagation and fracture behaviors during impact fragmentation is important and necessary for disaster evaluation of rockfalls. Discontinuous Deformation Analysis (DDA) incorporating virtual joints can offer a powerful tool to solve such a problem. In the analysis process, the computational efficiency is critical because the mesh must be very dense to make crack propagation more realistic. Thus, parallel DDA using OpenMP is applied. The flattened and precrack Brazilian disc tests are first reproduced, respectively, to verify the accuracy and efficiency of the parallel DDA with virtual joints. Then, the impact fragmentation process is simulated and validated with corresponding laboratory experiments in terms of crack propagation results. Furthermore, the effects of joint-slope angle, joint connectivity rate, and impact velocity on rock fracture behaviors are investigated. It is concluded that the peak number of cracks occurs when the joint-slope angle ranges between 30° and 45°; the higher impact velocity and joint connectivity rate tend to cause more cracks and larger damages to the specimen.

scholarly journals A Stochastic Rockfall Model Related to Random Ground Roughness Based on Three-Dimensional Discontinuous Deformation Analysis

2021 ◽  
Vol 9 ◽  
Author(s):  
Lu Zheng ◽  
Zhiyuan Zhu ◽  
Qi Wei ◽  
Kaihui Ren ◽  
Yihan Wu ◽  
...  
Keyword(s):  
Dynamic Behavior ◽  
Lateral Displacement ◽  
Grid Point ◽  
Slope Angle ◽  
Three Dimensional ◽  
Discontinuous Deformation Analysis ◽  
Cumulative Distribution ◽  
Deformation Analysis ◽  
Discontinuous Deformation ◽  
The Impact

The use of feasible 3-D numerical methods has become essential for addressing problems related to rockfall hazard. Although several models with various degrees of complexity are available, certain trajectories and impact dynamics related to some model inputs could fall in the rockfall observations area but are rarely calibrated against reflecting its range, especially the lateral deviations. A major difficulty exists in the lack of simulating the apparent randomness during the impact-rebound process leading to both ground roughness and block irregularities. The model presented here is based on three-dimensional discontinuous deformation analysis (3-D DDA). Despite similarities to previous simulations using 3-D DDA, the model presented here incorporates several novel concepts: (1) ground roughness is represented as a random change of slope angle by height perturbation at a grid point in DEM terrain; (2) block irregularities are modelled directly using polyhedron data; (3) a scaled velocity restitution relationship is introduced to consider incident velocity and its angle. Lateral deviations of rebound velocity, both direction and value, at impact are similarly accounted for by perturbing the ground orientation laterally, thus inducing scatter of run-out directions. With these features, the model is capable to describe the stochastic rockfall dynamics. In this study, 3-D DDA was then conducted to investigate the dynamic behavior of the rockfall and examine the role of sphericity of the rock block travelling on bench slopes with different ground roughness levels. Parametric analyses were carried out in terms of cumulative distribution function (CDF) to investigate for spatial distribution (both runout distance and lateral displacement), velocity and jumping height. The effects of block shape and ground roughness revealed by these factors were discussed. It suggests that ground roughness amplifies the randomness and plays important roles on the dynamic behavior of the system; irregularity from block sphericity will further amplify the randomness especially when the size of the rock is relatively small compared to the roughness level. Both irregularities should be taken into consideration in simulating rockfall problems. Further calibration of the new model against a range of field datasets is essential.

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.

Study on the Impact of Lateral Pressure on Jointed Rock Mass with DDARF Method

2014 ◽  
Vol 1044-1045 ◽  
pp. 607-611
Author(s):  
Cheng Long Zhao ◽  
Wei Shen Zhu ◽  
Shu Cai Li ◽  
Hai Ping Ma
Keyword(s):  
Compression Test ◽  
Lateral Pressure ◽  
Jointed Rock ◽  
Discontinuous Deformation Analysis ◽  
Biaxial Compression ◽  
Deformation Analysis ◽  
Inhibiting Effect ◽  
Discontinuous Deformation ◽  
The Impact ◽  
Initiation Stress

The discontinuous deformation analysis for rock failure (DDARF) method is adopted to simulate the biaxial compression test under different lateral pressure conditions. Then this paper analyzes the impact of the lateral pressure on the specimen failure rules. The simulation results show that the lateral pressure has obvious inhibiting effect on the expansion of wing cracks, crack initiation stress, and specimen peak strength.Keywords: Multi-joint specimen; DDARF method; Lateral pressure; Biaxial compression test simulation

scholarly journals Influence of “X” Fracture, Confining Pressure, and Temperature on Rock Masses’ Failure Process

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yunjuan Chen ◽  
Yi Jing ◽  
Yanchun Yin ◽  
Fuqiang Yin ◽  
Chenglong Zhao
Keyword(s):  
Crack Propagation ◽  
Similarity Theory ◽  
Failure Process ◽  
Confining Pressure ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Confining Pressures ◽  
Discontinuous Deformation ◽  
Loading And Unloading ◽  
Cracking Process

Based on the similarity theory, sandstone was taken as the prototype, and rock-like specimens were made with the strength ratio of 1 : 1. Single “X” fracture and double “X” fractures were prefabricated in rock-like specimen, and crack propagation was studied through the compressive test. An improved discontinuous deformation analysis method (DDARF) was adopted to simulate on the cracking process. Further, other factors should not be ignored such as confining pressure and temperature, which were considered: rock’s crack propagations under loading and unloading with different confining pressures were studied; influences of temperature from 20°C to 300°C on crack propagation were analyzed.

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.

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