Fracture Behavior and Water Migration in Heterogeneous and Porous Rocks

2005 ◽  
Vol 297-300 ◽  
pp. 2636-2641
Author(s):  
Lian Chong Li ◽  
Leslie George Tham ◽  
Tian Hong Yang ◽  
Xia Li
Keyword(s):  
Fluid Flow ◽  
Fracture Behavior ◽  
Rock Sample ◽  
Process Analysis ◽  
Failure Process ◽  
Compressive Loading ◽  
Porous Rocks ◽  
Rock Failure Process ◽  
Strength Character ◽  
Weak Zones

Based on the heterogeneous and porous characteristics of rock materials, a flow-stressdamage (FSD) model, implemented with the Rock Failure Process Analysis code (RFPA2D), is used to investigate the behavior of fluid flow and damage evolution, and their coupling action in rock sample that are subjected to both hydraulic and uniaxial compressive loading. A highly heterogeneous sample, containing grains, grain boundaries and weak zones, is employed in the numerical simulation. The simulation results provide a deep insight in the physical essence of the evolutionary nature of fracture phenomena as well as the fluid flow in heterogeneous materials, especially when they are highly stressed. The simulation result suggests that the nature of fluid flow and strength character in rocks strongly depends upon the heterogeneity of the rocks.

Numerical Simulation on 3-D Crack Coalescence in Rock-Like Materials Containing Pre-Existing Surface Closed Flaws

2006 ◽  
Vol 324-325 ◽  
pp. 69-72 ◽  
Author(s):  
Yu Jun Zuo ◽  
Chun An Tang ◽  
Zheng Zhao Liang ◽  
Yong Bin Zhang
Keyword(s):  
Process Analysis ◽  
Failure Process ◽  
Compressive Loading ◽  
Crack Coalescence ◽  
3 Dimensional ◽  
Plastic Materials ◽  
Secondary Cracks ◽  
Rock Failure Process ◽  
Type C ◽  
Mode A

Using newly developed 3 dimensional Rock Failure Process Analysis code RFPA3D, numerical simulations on samples of rock-like material containing pre-existing surface closed flaws under uniaxial compressive loading are conducted to investigate the failure mechanism and crack coalescence modes. Friction in closed flaws is modeled by inserting ideal elasto-plastic materials into the flaws. The simulations replicate most of the phenomena observed in actual experiments, such as initiation and growth of wing and secondary cracks, crack coalescence, and the macro-failure of the sample. For the samples containing three pre-existing surface closed flaws, four different patterns of crack coalescence are obtained in our simulations. The four different patterns of coalescence are the combination of T mode, S mode, TS mode and C mode, i.e. type (C+S mode), (T+S mode), (S mode) and (C+S mode). A total of four types of samples containing three surface parallel inclined frictional flaws are numerically simulated.

Numerical Analysis of Faults on Deep-Buried Tunnel Surrounding Rock Damaged Zones

2011 ◽  
Vol 90-93 ◽  
pp. 74-78 ◽  
Author(s):  
Jun Hu ◽  
Ling Xu ◽  
Nu Wen Xu
Keyword(s):  
Numerical Analysis ◽  
Mechanical Response ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Water Inrush ◽  
Surrounding Rock ◽  
Factors Affecting ◽  
Rock Failure Process ◽  
Tunnel Instability

Fault is one of the most important factors affecting tunnel instability. As a significant and casual construction of Jinping II hydropower station, when the drain tunnel is excavated at depth of 1600 m, rockbursts and water inrush induced by several huge faults and zone of fracture have restricted the development of the whole construction. In this paper, a progressive failure progress numerical analysis code-RFPA (abbreviated from Rock Failure Process Analysis) is applied to investigate the influence of faults on tunnel instability and damaged zones. Numerical simulation is performed to analyze the stress distribution and wreck regions of the tunnel, and the results are consistent with the phenomena obtained from field observation. Moreover, the effects of fault characteristics and positions on the construction mechanical response are studied in details. Some distribution rules of surrounding rock stress of deep-buried tunnel are summarized to provide the reasonable references to TBM excavation and post-support of the drain tunnel, as well as the design and construction of similar engineering in future.

Numerical Simulation on Failure Patterns of Rock Discs and Rings Subject to Diametral Line Loads

2004 ◽  
Vol 261-263 ◽  
pp. 1517-1522 ◽  
Author(s):  
Wan Cheng Zhu ◽  
K.T. Chau ◽  
Chun An Tang
Keyword(s):  
Tensile Strength ◽  
Standardized Test ◽  
Process Analysis ◽  
Failure Process ◽  
Brazilian Test ◽  
Rock Failure ◽  
Numerical Code ◽  
Failure Patterns ◽  
Rock Failure Process ◽  
Indirect Tensile

Brazilian test is a standardized test for measuring indirect tensile strength of rock and concrete disc (or cylinder). Similar test called indirect tensile test has also been used for other geomaterials. Although splitting of the disc into two halves is the expected failure mode, other rupture modes had also been observed. More importantly, the splitting tensile strength of rock can vary significantly with the specimen geometry and loading condition. In this study, a numerical code called RFPA2D (abbreviated from Rock Failure Process Analysis) is used to simulate the failure process of disc and ring specimens subject to Brazilian test. The failure patterns and splitting tensile strengths of specimens with different size and loading-strip-width are simulated and compared with existing experimental results. In addition, two distinct failure patterns observed in ring tests have been simulated using RFPA2D and thus this verifies the applicability of RFPA2D in simulating rock failure process under static loads.

The Influence of Stress Ratio on the Fracture Behavior of Brittle Materials

2007 ◽  
Vol 353-358 ◽  
pp. 937-940
Author(s):  
Wei Hong Li ◽  
Xiong Chen ◽  
De Shen Zhao ◽  
Yi Wang Bao
Keyword(s):  
Stress State ◽  
Fracture Behavior ◽  
Stress Ratio ◽  
Process Analysis ◽  
Failure Process ◽  
Brittle Materials ◽  
Simulation Method ◽  
Critical Stress Intensity Factor ◽  
Complex Stress State ◽  
Biaxial Stress

The fracture behavior of brittle materials under different stress ratio has been investigated by means of numerical simulation method with software RFPA2D (Realistic Failure Process Analysis). The fracture dependence of brittle material on biaxial plane stress state was confirmed. The results show that the critical stress intensity factor under biaxial stress increases with the increase of biaxial stress ratio. The simulation tests reveal that the biaxial stresses have strong influence on the fracture properties of glass. The results confirmed that the strain criterion of fracture is feasible while brittle materials under complex stress state.

Numerical Investigation for Fracture Saturation in Multilayer Sedimentary Rock in Unsymmetrical Case

2013 ◽  
Vol 690-693 ◽  
pp. 3050-3053
Author(s):  
Feng Shan Han ◽  
Li Song
Keyword(s):  
Numerical Simulation ◽  
Layer Thickness ◽  
Sedimentary Rock ◽  
Process Analysis ◽  
Failure Process ◽  
Bottom Layer ◽  
Thickness Ratio ◽  
Fracture Spacing ◽  
Layer Thickness Ratio ◽  
Rock Failure Process

Opening mode fractures in multilayer sedimentary rock often are periodically distributed with fracture spacing scaled to the thickness of the fractured layer. In this paper, based on Rock Failure Process Analysis Code RFPA2D, a three layer model with a central layer and with the different thickness top and bottom layer, progressive formation in multilayer sedimentary rock at fracture saturation in unsymmetrical case is simulated. We investigate the change of the critical fracture spacing to layer thickness ratio as a function of the thickness of the top layer where the bottom layers is much thicker (5 times) than the fractured layer called the unsymmetrical case, in this unsymmetrical case, fracture saturation is simulated. By numerical simulation of RFPA2D, the critical spacing to layer thickness ratio decreases and tend to the same constant value as the thickness of the top layer increases. Numerical simulation shown that for the unsymmetrical case, if the adjacent layers are thicker than 1.5 times the thickness of the fractured layer, the multilayer sedimentary rock can be treated approximately as a system with infinitely thick top and bottom layers at fracture saturation.That should be useful in the design of engineering systems and in the prediction of fracture spacing in hydrocarbon reservoirs and groundwater aquifers.

scholarly journals Numerical Analysis on Failure Modes and Mechanisms of Mine Pillars under Shear Loading

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Tianhui Ma ◽  
Long Wang ◽  
Fidelis Tawiah Suorineni ◽  
Chunan Tang
Keyword(s):  
Failure Modes ◽  
Process Analysis ◽  
Failure Process ◽  
Effective Means ◽  
Shear Loading ◽  
Shear Stresses ◽  
Planning And Design ◽  
Rock Failure Process ◽  
Damage Process ◽  
Dip Angle

Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA) 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars.

scholarly journals Relationship between Movement Laws of the Overlaying Strata and Time Space of the Mined-Out Volume

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Xiang Yu ◽  
Kang Zhao ◽  
Qing Wang ◽  
Yajing Yan ◽  
Yongjun Zhang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Process Analysis ◽  
Failure Process ◽  
Failure Behavior ◽  
Overburden Rock ◽  
Deformation And Failure ◽  
Working Face ◽  
Time Space ◽  
Rock Failure Process ◽  
Function Relationship

The study and accurate prediction of the movement of overburden rock mass and surface subsidence are crucial for a safe production in metal mines. This study investigates the relationship between the movement laws of overlaying strata and the time space of a mined-out volume using Rock Failure Process Analysis (RFPA) System. Furthermore, the movement, deformation, and failure laws of overlaying strata are examined in different positions when a goaf volume is certain and the failure behavior of the overlaying strata. This study analyzes the similarities and differences of the overlaying strata comparatively. Results show that, regardless of the movement range or subsidence value of the overlying rock mass, a power function relationship is observed between them and working face advancement. Setting the equation shows that the scope of the overlying rock mass is significant when the ratio of a certain position distance roof to the working face distance is small. The results provide a reference for controlling the displacement of the overlying rock mass and treating goaf.

scholarly journals A Crack Propagation Control Study of Directional Hydraulic Fracturing Based on Hydraulic Slotting and a Nonuniform Pore Pressure Field

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Yugang Cheng ◽  
Zhaohui Lu ◽  
Xidong Du ◽  
Xuefu Zhang ◽  
Mengru Zeng
Keyword(s):  
Crack Initiation ◽  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Pressure Field ◽  
Process Analysis ◽  
Failure Process ◽  
Horizontal Stress ◽  
Directional Hydraulic Fracturing ◽  
Rock Failure Process ◽  
Initiation Pressure

Hydraulic fracturing techniques for developing deeply buried coal reservoirs face routine problems related to high initial pressures and limited control over the fracture propagation direction. A novel method of directional hydraulic fracturing (DHF) based on hydraulic slotting in a nonuniform pore pressure field is proposed. A mechanical model is used to address crack initiation and propagation in a nonuniform pore pressure field, where cracks tend to rupture and propagate towards zones of high pore pressure for reducing the effective rock stress more. The crack initiation pressure and propagation morphology are analyzed by rock failure process analysis software. The numerical results show that the directional propagation of hydraulic fracturing cracks is possible when the horizontal stress difference coefficient is less than or equal to 0.5 or the slotting deviation angle is less than or equal to 30°. These findings are in good agreement with experimental results, which support the accuracy and reliability of the proposed method and theory.

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