Numerical Simulation of the Influence of Grain Size on the Progressive Development of Brittle Failure in Yuen Long Marbles

2004 ◽  
Vol 261-263 ◽  
pp. 1511-1516 ◽  
Author(s):  
Ming Ruo Jiao ◽  
R.H.C. Wong ◽  
T.F. Wong ◽  
K.T. Chau ◽  
Chun An Tang
Keyword(s):  
Numerical Simulation ◽  
Experimental Study ◽  
Grain Size ◽  
Progressive Failure ◽  
Process Analysis ◽  
Failure Process ◽  
Systematic Investigation ◽  
Failure Behavior ◽  
Progressive Development ◽  
Brittle Rocks

It has long been recognized that the strength of brittle rocks decreases with the grain size. However, very few systematic investigation of this phenomenon has been made using numerical method. This paper presents the results of a numerical simulation using the Rock Failure Process Analysis code (RFPA2D) to investigate the effects of grain size on the uniaxial compressive strength and the failure behavior of Yuen Long marble. The Weibull distribution with two parameters (m that characterizes the strength heterogeneity, and σ0 that corresponds to the mean strength of an element) selected based on micromechanical basis is used in the RFPA2D code for simulation. The simulated stress-strain curves of Yuen Long marbles with different grain sizes under uniaxial compressive condition agrees well with the experimental study. The progressive failure process was captured in the numerical simulations. Our simulations also reproduced the influence of grain size, with strength scaling approximately with the inverse square root of grain size, which is in agreement with the previous experimental study.

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.

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 Fracture Formation on Surfaces of Bi-Layered Materials

2007 ◽  
Vol 353-358 ◽  
pp. 993-996
Author(s):  
Tian Hui Ma ◽  
Ju Ying Yang ◽  
Zheng Zhao Liang ◽  
Yong Bin Zhang ◽  
Tao Xu
Keyword(s):  
Numerical Simulation ◽  
Numerical Solutions ◽  
Process Analysis ◽  
Failure Process ◽  
Layered Materials ◽  
Numerical Code ◽  
Material Layer ◽  
Fracture Formation ◽  
Constant State ◽  
The Individual

Fracture formation on surfaces of bi-layered materials is studied numerically. A simplified two-layered materials model like growing tree trunk is present. This work is focused on patterns of fractures and fracture saturation. We consider the formation of crack pattern in bark as an example of pattern formation due to expansion of one material layer with respect to another. As a result of this expansion, the bark stretches until it reaches its limit of deformation and cracks. A novel numerical code, 3D Realistic Failure Process Analysis code (abbreviated as RFPA3D) is used to obtain numerical solutions. In this numerical code, the heterogeneity of materials is taken into account by assigning different properties to the individual elements according to statistical distribution function. Elastic-brittle constitutive relation with residual strength for elements and a Mohr-Coulomb criterion with a tensile cut-off are adopted so that the elements may fail either in shear or in tension. The discontinuity feature of the initiated crack is automatically induced by using degraded stiffness approach when the tensile strain of the failed elements reaching a certain value. The different patterns are obtained by varying simulation parameters, the thickness of the material layer. Numerical simulation clearly demonstrates that the stress state transition precludes further infilling of fractures and the fracture spacing reaches constant state,i.e. the socalled fracture saturation. It also indicates that RFPA code is a viable tool for modeling fracture formation and studying fracture patterns.

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 Failure Behavior of F Shape Non-Persistent Joint under Experimental and Numerical Uniaxial Compression Test

2021 ◽  
Author(s):  
vahab sarfarazi ◽  
kaveh asgari ◽  
meisam zarei
Keyword(s):  
Numerical Simulation ◽  
Compression Test ◽  
Experimental Testing ◽  
Failure Process ◽  
Particle Flow Code ◽  
Failure Behavior ◽  
Uniaxial Compression Test ◽  
Joint Angles ◽  
Large Joint ◽  
Load Rate

Abstract Experimental and discrete element approaches were used to examine the effects of F shape non-persistent joints on the failure behaviour of concrete under uniaxial compressive test. concrete specimens with dimensions of 200 mm×200 mm×50 mm were provided. Within the specimen, F shape non-persistent joint consisting three joints were provided. The large joint length was 6 cm, and the length of two small joints were 2cm. Vertical distance betwenn two small joints change from 1.5 cm to 4.5 cm with increment of 1.5 cm. In constant joint lengths, the angle of large joint change from 0 to 90 with increments of 30. Totally 12 different models were tested under compression test. The axial load rate on the model was 0.05 mm/min. Cuncurrent with experimental tests, numerical simulation (Particle flow code in two dimension) were performed on the models containing F shape non-persistent joint. Distance between small joints and joint angles were similar to experimental one. the results indicated that the failure process was mostly governed by both of the Distance between small joints and joint angles. The compressive strengths of the samples were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. In the first There were only a few AE hits in the initial stage of loading, then AE hits rapidly grow before the applied stress reached its peak. Furthermore, a large number of AE hits accompanied every stress drop. Finally, the failure pattern and failure strength are similar in both approaches i.e. the experimental testing and the numerical simulation approaches.

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.

Application of RFPA2D in Sublevel Caving Mining Extra-Thick Coal Seams

2008 ◽  
Vol 575-578 ◽  
pp. 1246-1251 ◽  
Author(s):  
Hua Nan ◽  
Tao Xu ◽  
Zhi Dong Wei
Keyword(s):  
Numerical Simulation ◽  
Process Analysis ◽  
Failure Process ◽  
Coal Seams ◽  
Simulation Test ◽  
Parameters Selection ◽  
Sublevel Caving ◽  
High Efficient ◽  
Measurement Results ◽  
Suitable Arrangement

On the basis of suitable arrangement for the special stress surrounding and parameters selection, Realistic Failure Process Analysis 2-D (RFPA2D) numerical simulation of extra-thick coal seams’ displacement and failure is carried out. It’s proved that the numerical simulation results are consistent with the in-sit measurement results of top coal’s advance supporting stress and deep-hole displacement. So application of RFPA2D in sub-level caving mining extra-thick coal seams is reliable. It’s also proved that application of RFPA2D in sub-level caving mining can do great help to study the nature of top coal’s displacement, fragmentation and failure process of extra-thick coal seams. As the top coal’s displacement and failure situation under certain circumstance can be forecasted by RFPA2D numerical simulation, the most suitable top coal thickness under certain circumstance can be predicted by RFPA2D numerical simulation test, which can do great benefit to extra-thick coal seams’ safe and high efficient mining.

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