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Journal of Central South University 2015年第11期22卷 4291-4299页

作者： Nooraddin Nikadat Mohammad Fatehi abolfazl abdollahipour Mining & Metallurgical Engineering Yazd University

Tunnels are one of the major transportation routes to pass mountains and difficult geological conditions. The behavior of these structures is significantly influenced by rock mass and discontinuities. Orientation of discontinuities is one of the most important geometrical parameters affecting discontinuities behavior. The effect of large discontinuities(faults) behavior on a jointed medium around rectangular tunnels is studied. A hybridized indirect boundary element code named TFSDDM(fictitious stress displacement discontinuity method) is used to study the stress distribution around the tunnels excavated in jointed rock masses. The code uses advantages of both fictitious stress and displacement discontinuity methods to analyze discontinuity effects more accurately. Results show that the dip angle of discontinuities has significant effect on stress distribution around the tunnel. It is also shown that increase in the discontinuities dip angle located in the roof will result in decrease in tensile stress of the roof. Stresses reaches to 8 MPa in the roof while due to dilation effect they reach up to 13 MPa.

关键词： displacement discontinuity method fictitious stres

Stability analysis and determination of rock pillar between two adjacent caverns in different regions of Asmari formation in Iran

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International Journal of Mining Science and Technology 2014年第5期24卷 593-596页

作者： abdollahipour abolfazl Ghannadshirazi Hossein Faculty of Mining and Metallurgical Engineering Yazd University Yazd 89195-741 Iran Mining Engineering Group Shahid Bahonar University of Kerman Kerman 76175-133 Iran

Large underground caverns are commonly used in variety of applications. In many cases, because of the geomechanical limitations of dimensions and requirement of high volume, several parallel caverns are used. Plastic zone integration requires a larger rock pillar distance of theses adjacent caverns while eco- nomic and access reasons require smaller distance. In lran many underground projects are located in West and South West, Asmari formation covers a large part of these regions. The stability of underground spaces that are constructed or will be constructed in this formation has been investigated. A proper cross section based on plastic analysis and a stability criterion has been proposed for each region. Finally, in each case, allowable rock pillar between adjacent caverns with similar dimension was determined with two methods （numerical analysis and fire service law）. Results show that Fire Service Law uses a very con- servative safety factor and it was proposed to use a correction factor for allowable distance based on application of underground space.

关键词： Stability analysis Storage cavern Numerical analysis Rock pillar Asmari formation

Sensitivity analysis of influencing parameters in cavern stability

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International Journal of Mining Science and Technology 2012年第5期22卷 707-710页

作者： abolfazl abdollahipour Reza Rahmannejad Mining and Metallurgical Department Yazd UniversityYazd 89195-741Iran Mining Engineering Group Shahid Bahonar University of KermanKerman 76175-133Iran

In order to analyze the stability of the underground rock structures,knowing the sensitivity of geomechanical parameters is *** investigate the priority of these geomechanical properties in the stability of cavern,a sensitivity analysis has been performed on a single cavern in various rock mass qualities according to RMR using Phase *** stability of cavern has been studied by investigating the side wall *** showed that most sensitive properties are coefficient of lateral stress and modulus of *** parameters of Hoek-Brown criterion and r c have no sensitivity when cavern is in a perfect elastic *** in an elasto-plastic state,parameters of Hoek-Brown criterion and r c affect the deformability;such effect becomes more remarkable with increasing plastic *** parameters have different sensitivities concerning rock mass quality(RMR).Results have been used to propose the best set of parameters for study on prediction of sidewall displacement.

关键词： Sensitivity analysis Cavern stability Numerical methods RMR rating system

On the accuracy of higher order displacement discontinuity method(HODDM) in the solution of linear elastic fracture mechanics problems

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Journal of Central South University 2016年第11期23卷 2941-2950页

作者： abolfazl abdollahipour Mohammad Fatehi Marji Alireza Yarahmadi Bafghi Javad Gholamnejad Faculty of Mining and Metallurgical Engineering Yazd University

The higher order displacement discontinuity method(HODDM) utilizing special crack tip elements has been used in the solution of linear elastic fracture mechanics(LEFM) problems. The paper has selected several example problems from the fracture mechanics literature(with available analytical solutions) including center slant crack in an infinite and finite body, single and double edge cracks, cracks emanating from a circular hole. The numerical values of Mode Ⅰ and Mode Ⅱ SIFs for these problems using HODDM are in excellent agreement with analytical results(reaching up to 0.001% deviation from their analytical results). The HODDM is also compared with the XFEM and a modified XFEM results. The results show that the HODDM needs a considerably lower computational effort(with less than 400 nodes) than the XFEM and the modified XFEM(which needs more than 10000 nodes) to reach a much higher accuracy. The proposed HODDM offers higher accuracy and lower computation effort for a wide range of problems in LEFM.

关键词： accuracy higher order displacement discontinuity method LEFM mode Ⅰ stress intensity factor mode Ⅱ stress intensity factor

Numerical simulation of fatigue crack propagation in heterogeneous geomaterials under varied loads using displacement discontinuity method

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 702-716页

作者： Rezvan Alizadeh Mohammad Fatehi Marji abolfazl abdollahipour Mehdi Pourghasemi Sagand Department of Mining and Metallurgical Engineering Faculty of EngineeringYazd UniversityYazdIran School of Mining Engineering College of EngineeringUniversity of TehranTehranIran

Heterogeneous brittle geomaterials are highly susceptible to cyclic *** contain inherent flaws and cracks that grow under fatigue loads and lead to *** study presents a numerical model for analyzing fatigue in these materials based on the two-dimensional(2D)boundary element method and linear elastic fracture *** process is formulated by coupling the displacement discontinuity method with the incorporation technique of dissimilar regions and the governing equations of *** heterogeneous media are assumed to consist of materials with different properties,and the interfaces are assumed to be completely *** addition,the domains include multiple cracks exposed to constant and variable amplitude cyclic *** stress intensity factor is a crucial parameter in fatigue analysis,which is determined using the displacement field around crack *** incremental crack growth scheme is applied to calculating the fatigue *** growth rate values are employed to estimate the length of crack extension when there are multiple *** interaction between cracks is considered,which also includes the coalescence ***,various structures under different cyclic loads are examined to evaluate the accuracy of this *** results demonstrate the efficiency of the proposed approach in modeling fatigue crack growth and life *** behavior of life curves for the heterogeneous domain was as *** curves illustrate the breakpoints caused by utilizing discrete incremental life *** these points,the trend of the curves changed with the material properties and fatigue characteristics of the new material around the crack tips.

关键词： Fatigue life Crack coalescence Interface Incorporation technique Variable amplitude loading

DEM simulation of confining pressure effects on crack opening displacement in hydraulic fracturing

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International Journal of Mining Science and Technology 2016年第4期26卷 557-561页

作者： abdollahipour abolfazl Fatehi Marji Mohammad Yarahmadi Bafghi Alireza Gholamnejad Javad Faculty of Mining and Metallurgical Engineering Yazd University

Hydraulic fracture is one of the key methods in well stimulation to increase production of oil and *** Opening Displacement(COD) is of great importance in this method since it is in direct relation with permeability and production *** this paper COD is measured by a distinct element model which has been validated by an exact solution.A comprehensive study has been performed on confining pressure effect on COD which is neglected in the analytical *** results showed that confining pressure considerably affects COD.A multi-parameter regression(considering effect of confining pressure,rock mass properties and fluid pressure) was performed on numerical results which resulted in an *** proposed equation considers the effect of confining pressure and its results are in good agreement with numerical results.

关键词： Hydraulic lracture COD Numerical analysis Confining pressure Regression

Sensitivity analysis of geomechanical parameters affecting a wellbore stability

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Journal of Central South University 2019年第3期26卷 768-778页

作者： abolfazl abdollahipour Hamid SOLTANIAN Yaser POURMAZAHERI Ezzatollah KAZEMZADEH Mohammad FATEHI-MARJI Division of Petroleum Engineering Faculty of Upstream Petroleum Industry Research Institute of Petroleum Industry (RIPI) Faculty of Mining and Metallurgical Engineering Yazd University

Wellbore stability analysis is a growing concern in oil industries. There are many parameters affecting the stability of a wellbore including geomechanical properties (e.g., elastic modulus, uni-axial compressive strength (UCS) and cohesion) and acting forces (e.g., field stresses and mud pressure). Accurate determination of these parameters is time-consuming, expensive and sometimes even impossible. This work offers a systematic sensitivity analysis to quantify the amount of each parameter’s effect on the stability of a wellbore. Maximum wellbore wall displacement is used as a stability factor to study the stability of a wellbore. A 3D finite difference method with Mohr model is used for the numerical modeling. The numerical model is verified against an analytical solution. A dimensionless sensitivity factor is developed in order to compare the results of various parameters in the sensitivity analysis. The results show a different order of importance of parameters based on rock strength. The most sensitive properties for a weak rock are the maximum horizontal stress, internal friction angle and formation pressure, respectively, while for a strong rock, the most sensitive parameters are the maximum horizontal stress, mud pressure and pore pressure, respectively. The amount of error in wellbore stability analysis inflicted by the error in estimation of each parameter was also derived.

关键词： wellbore stability sensitivity analysis numerical modeling