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 Study of Elastic-Brittle Failure of Notched Openings in Rocks

2005 ◽  
Vol 297-300 ◽  
pp. 2605-2611
Author(s):  
Shan Yong Wang ◽  
S.K. Au ◽  
K.C. Lam ◽  
Chun An Tang
Keyword(s):  
Numerical Study ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Confining Pressure ◽  
Numerical Code ◽  
Tunnel Wall ◽  
Model Studies ◽  
Borehole Breakout ◽  
Rock Failure Process

Borehole breakout is the process by which portions of borehole or tunnel wall fracture or spall when subjected to compressive stresses. The stress-strain characteristics of rock during loading and unloading confining pressure are studied firstly. To overcome the difficulties in analytical model studies, a numerical code, RFPA2D (Rock Failure Process Analysis), developed by CRISR, Northeastern University, China, is used to investigate the progressive failure of breakout around tunnel. The heterogeneity of rock was also taken into account in the software. The numerical simulation reproduces the formation notch in rocks by the growth, interaction and coalescence of randomly distributed macrocracks. It is illustrated from the numerical simulated results that breakout direction of tunnel is parallel with the minor stress tensor in the plane perpendicular to the borehole axis. Specifically due to the inclusion of heterogeneity, some peculiarities are studied both in the evolution of fracture and the influence of borehole on the peak intensity of specimen as well as the AE event patterns.

Micromechanics and Rock Failure Process Analysis

2004 ◽  
Vol 261-263 ◽  
pp. 39-44 ◽  
Author(s):  
T.F. Wong ◽  
R.H.C. Wong ◽  
Ming Ruo Jiao ◽  
K.T. Chau ◽  
Chun An Tang
Keyword(s):  
Grain Size ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Realistic Model ◽  
Rock Failure ◽  
Failure Behavior ◽  
Microstructural Parameters ◽  
Rock Failure Process ◽  
Two Parameters

A major challenge in rock mechanics has been the realistic modeling that can reveal the progressive accumulation of damage and shear localization in a brittle rock under compression. The Rock Failure Process Analysis code (RFPA2D) is an efficient tool and realistic model to simulate such complexities. A key assumption of the code is that the heterogeneity of elastic moduli and failure strength are characterized by the Weibull distribution with two parameters (m and σ0 ). However, these two parameters do automatically not relate to the microstructural parameters, such as grain size and microcrack statistics. Therefore, the purpose of this paper is to elucidate the micromechanical basis of these Weibull parameters, specifically how they depend on microstructural attributes such as grain size and crack statistics. Secondly, a methodology was developed to quantitatively determine the relevant micromechanical parameters for input into the RFPA2D code. Finally, the methodology was implemented by quantifying the microcrack geometry and statistics of real rock and simulating its uniaxial compression and progressive failure behavior. The simulated result agrees well with the experimental study.

scholarly journals A Numerical Investigation on the Hydraulic Fracturing Effect of Water Inrush during Tunnel Excavation

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-15
Author(s):  
Quan Zhang ◽  
Bingxiang Huang ◽  
Manchao He ◽  
Shan Guo
Keyword(s):  
Stress Concentration ◽  
Hydraulic Fracturing ◽  
Process Analysis ◽  
Failure Process ◽  
Water Inrush ◽  
Water Source ◽  
Stress Concentrations ◽  
Karst Cavity ◽  
Effect Of Water ◽  
Rock Failure Process

When a high-pressure water source is located near a tunnel under excavation, water inrush is commonly associated with a hydraulic fracturing effect. To study the hydraulic fracturing effect of water inrush (HFEWI), flow-rock failure process analysis (F-RFPA2D) was adopted to simulate the water inrush process. The simulated results indicated that a stress disturbance area formed in front of the excavation face and that a hydraulic fracture zone formed in front of the karst cavity. Similarly, stress concentrations formed in front of the excavation face and the karst cavity. The hydraulic fracturing effect was characterized by stress concentration, and the local hydraulic crack propagation was the result of stress concentration. In addition, a pore pressure gradient formed in the crack-free area of the surrounding rock, and the occurrence of hydraulic cracking was the root cause of the significant change in water flow. When the hydraulic cracks initially formed and expanded, the zone of crack activity was large. As the cracks continued to expand, the range of activity decreased and finally concentrated directly in front of the excavation face. Additionally, the shapes of the water inrush channel obtained by the experimentation and numerical simulation were basically the same: semielliptical. During the evolution of hydraulic crack initiation, expansion, and penetration, the bottom of the excavated borehole was initially dry and then experienced seepage and water inrush. Finally, the minimum safe thickness of the rock wall was calculated to provide a safety guideline for this type of water inrush.

Digital Image Based Simulation on Failure Process of Heterogeneous Brittle Materials

2006 ◽  
Vol 324-325 ◽  
pp. 315-318
Author(s):  
Wan Cheng Zhu ◽  
Jin Chao Duan ◽  
Chun An Tang ◽  
Shan Yong Wang
Keyword(s):  
Digital Image ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Brittle Materials ◽  
Heterogeneous Material ◽  
Numerical Code ◽  
Mechanical Responses ◽  
Macro Scale ◽  
Rock Failure Process

Rock and concrete are typical heterogeneous material that the meso-scale heterogeneity may have a significant effect on their macro-scale mechanical responses. In this work, a digital image-based (DIB) technique is employed to characterize and quantify the heterogeneity of concrete, and the obtained data is directly imported into a numerical code named RFPA (Rock Failure Process Analysis) to study the effect of heterogeneity on the failure process of concrete. The upgraded RFPA is capable to simulate the progressive failure of brittle materials such as rock and concrete, representing both the growth of existing fractures and the formation of new fractures, obviating the need to identify crack tips and their interaction explicitly. The simulated results are in reasonable agreement with experimental measurements and phenomenological observations reported in previous studies.

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.

Acoustic Emission Characteristics of Rock Failure under Uniaxial Loading

2011 ◽  
Vol 378-379 ◽  
pp. 43-46 ◽  
Author(s):  
Tao Xie ◽  
Qing Hui Jiang ◽  
Rui Chen ◽  
Wei Zhang
Keyword(s):  
Acoustic Emission ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Progressive Failure ◽  
Failure Process ◽  
Testing Machine ◽  
Rock Failure ◽  
Rock Failure Process ◽  
State Variation ◽  
Acoustic Emission Test

With RMT-150C rock testing machine and AEWIN E1.86 DISP acoustic emission system applied, the acoustic emission test was accomplished with two kinds of rock samples including marble and granite under uniaxial compression. Cyclic loading and continuous loading were used through the experiment, and the mechanical performance and acoustic emission (AE) characteristics were obtained during the process of rock progressive failure. Details related to the relationship between amount of AE and stress-strain was given in this paper. A comparison between marble and granite was made as well following the general AE law, on the basis of which, the failure mechanism of rock mass was investigated. Finally, some conclusions can be summarized as follows:(1) AE activity features are different with stress state variation in rock failure process;(2) loading patterns make a direct impact on the failure process thereby affecting AE activities;(3)AE activities are various basing on the different types of rocks, structures and failure modes.

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.

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