scholarly journals DDA Simulation Study on Mechanical Failure of Heterogenous Rock

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Youjun Ning ◽  
Xinyang Lv ◽  
Zheng Yang
Keyword(s):  
Simulation Study ◽  
Failure Process ◽  
Mechanical Failure ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Rock Fracturing ◽  
Response Curves ◽  
Heterogeneity Index ◽  
Heterogeneous Rock ◽  
Dda Method

Heterogeneity is an important characteristic that affects the mechanical behavior of rock. In the present work, a statistical rock mesoheterogeneity model based on the Weibull distribution function is introduced into the discontinuous deformation analysis (DDA) method to simulate the mechanical failure of heterogeneous rock, in which the general heterogeneity degree is controlled by a heterogeneity index and the mechanical property of each subblock element is randomly assigned. Brazilian disc and uniaxial compressive rectangular specimens are simulated as examples. Results show that it is more reasonable to consider the heterogeneity of elasticity properties (the elastic modulus and Poisson’s ratio) and strength properties (the tensile strength, cohesion, and friction angle) simultaneously in the heterogeneity model. It is also shown that with a larger heterogeneity index, which means a lower degree of heterogeneity, the reproducibility of the macroscopic response curves of a specimen gets better, while the exact cracking always differs but with less scattered cracks, and the global fracturing failure pattern and mode are weakly influenced by the heterogeneity. Moreover, with the increase in the heterogeneity index, the macroscopic equivalent modulus and strength get larger and approach those of a homogeneous specimen. This work indicates the importance of heterogeneity for rock mechanical behaviors including the macroscopic equivalent response and the fracturing failure. By the subblock DDA method to simulate fracturing realistically, the fracturing failure process of heterogeneous rock can be successfully reproduced, which builds good foundation for the simulation study of heterogeneous rock fracturing in practical problems, e.g., coal and rock fracturing in fluidization mining in the future.

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.

Numerical Simulation of Coal Mining Excavation Based on Discontinuous Deformation Analysis

2011 ◽  
Vol 138-139 ◽  
pp. 187-192
Author(s):  
Ya Nan Gao ◽  
Feng Gao ◽  
M.R. Yeung ◽  
Qing Hui Jiang
Keyword(s):  
Underground Mining ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Rock Stratum ◽  
Deformation Problem ◽  
Excavation Process ◽  
Discontinuous Deformation ◽  
Movement And Deformation ◽  
Dda Method ◽  
The Continuum

The movement and deformation of rock stratum occur when the excavation is carries out during the underground mining process. Rock is a continuous-discontinuous material so the continuum mechanics method may not handle the rock problem well. The discontinuous deformation analysis (DDA) method which discretizes the rock mass to block system can describe the large displacement and deformation of rock blocks, especially the rock stratum collapse. The DDA was employed in this paper to analysis a mining excavation process. The displacement field and stress field of rock stratum was computed. The result shows that the DDA can handle the mining excavation and the rock stratum movement and deformation problem well.

DISCONTINUOUS DEFORMATION ANALYSIS BASED ON VARIATIONAL INEQUALITY THEORY

2011 ◽  
Vol 08 (02) ◽  
pp. 193-208 ◽  
Author(s):  
WEI JIANG ◽  
HONG ZHENG
Keyword(s):  
Variational Inequality ◽  
Variational Inequality Problem ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Penalty Function Method ◽  
Weak Nonlinearity ◽  
Contact Conditions ◽  
Inequality Theory ◽  
Discontinuous Deformation ◽  
Dda Method

In the conventional discontinuous deformation analysis (DDA) method, the contact conditions are enforced by the penalty function method. Improperly selected penalty parameters might cause numerical problems. In order to evade the introduction of the penalty parameters and to avoid "open–close iteration" that can not assure convergence, this study reformulates the DDA as a variational inequality problem. Based on the fact that the solution of a variational inequality is a fixed point of a natural projection map, the problem is reduced to the solution of nonsmooth equations with weak nonlinearity. Then, the Path Newton Method (PNM) is utilized to solve the equations. Some practical examples originally designed by Shi are reanalyzed, which demonstrates that the new DDA method is feasible.

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.

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.

scholarly journals Techniques for Progressive Failure Simulation of Hard Brittle Surrounding Rockmass: Taking the URL Test Tunnel as an Example

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Daning Zhong ◽  
Jianlin Chen ◽  
Hui Zhou ◽  
Xiangrong Chen ◽  
Yali Jiang ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Progressive Failure ◽  
Failure Process ◽  
High Stress ◽  
Constitutive Models ◽  
Discrete Element ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Underground Engineering ◽  
And Control

Accurate simulation of the failure process of hard brittle surrounding rockmass is very important for the analysis and control of the structural stability in deep underground engineering. In order to simulate the progressive failure process of the hard brittle surrounding rockmass, a continuous discontinuous deformation analysis method that couples the finite element and discrete element is adopted. Taking the URL test tunnel in Canada as an engineering case, the constitutive model of the contact considering the effects of cohesion weakening and friction strengthening is applied, and the 2D approximation to 3D excavation by applying elastic modulus reduction technology is adopted to simulate the range and depth of crack growth of the surrounding rockmass. Then, the comparison between simulated results and on-site monitoring results is performed, which shows good consistency. At the same time, the key factors in the numerical simulation of progressive failure in hard brittle rockmass are identified, including the number of elements, excavation effects, and constitutive models. The results show that the constitutive model determines the basic form of crack propagation, but in order to accurately simulate the progressive propagation of cracks, the number of elements must be sufficient enough and the effects of 3D excavation must be considered. The analysis accurately simulates the progressive failure characteristics of hard brittle surrounding rockmass under high stress, achieving the purpose of reasonably grasping the degree of damage to the surrounding rockmass, and provides technical reference and support on how to accurately simulate the failure of hard brittle surrounding rockmass using the finite discrete element method.

Simulation of Whole Movement Process of Muzhuping Landslide with DDA and Prediction of Surge

2014 ◽  
Vol 989-994 ◽  
pp. 2254-2257
Author(s):  
Zhi Hong Dong ◽  
Xiu Li Ding ◽  
Ai Qing Wu ◽  
Bo Lu
Keyword(s):  
Difficult Problem ◽  
Discontinuous Deformation Analysis ◽  
Deformation Analysis ◽  
Movement Process ◽  
River Reservoir ◽  
Discontinuous Deformation ◽  
Wave Induced ◽  
Surge Height ◽  
Landslide Movement ◽  
Dda Method

The surge wave induced by the landslide on reservoir bank is extremely disaster .The prediction of surge height is a difficult problem because the velocity of landslide is hard to obtain. The discontinuous deformation analysis (DDA) is able to simulate landslide movement with real time and acceleration. The whole movement process of Muzhuping landslide in the Qing river reservoir is simulated by DDA method, including startup, accelerating, deceleration and stop, and velocity along time is obtained. Last, empirical formula for computing surge height is discussed.

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