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| 1 | Cracks coalescence mechanism and cracks propagation paths in rock-like specimens containing pre-existing random cracks under compression显示文摘The mechanism of cracks propagation and cracks coalescence due to compressive loading of the brittle substances containing pre-existing cracks(flaws)was modeled experimentally using specially made rock-like specimens from Portland Pozzolana Cement(PPC).The breakage process of the specimens was studied by inserting single and double flaws with different inclination angles at the center and applying uniaxial compressive stress at both ends of the specimen.The first crack was oriented at 50° from the horizontal direction and kept constant throughout the analysis while the orientation of the second crack was changed.It is experimentally observed that the wing cracks are produced at the first stage of loading and start their propagation toward the direction of uniaxial compressive loading.The secondary cracks may also be produced in form of quasi-coplanar and/or oblique cracks in a stable manner.The secondary cracks may eventually continue their propagation in the direction of maximum principle stress.These experimental works were also simulated numerically by a modified higher order displacement discontinuity method and the cracks propagation and cracks coalescence were studied based on Mode I and Mode II stress intensity factors(SIFs).It is concluded that the wing cracks initiation stresses for the specimens change from 11.3 to 14.1 MPa in the case of numerical simulations and from 7.3 to 13.8 MPa in the case of experimental works.It is observed that cracks coalescence stresses change from 21.8 to 25.3 MPa and from 19.5 to 21.8 MPa in the numerical and experimental analyses,respectively.Comparing some of the numerical and experimental results with those recently cited in the literature validates the results obtained by the proposed study.Finally,a numerical simulation was accomplished to study the effect of confining pressure on the crack propagation process,showing that the SIFs increase and the crack initiation angles change in this case. | Hadi Haeri Kourosh Shahriar Mohammad Fatehi Marji Parviz Moarefvand | 2014 | Journal of Central South University2014，21，6： | 16 |
| 2 | Numerical analysis of confinement effect on crack propagation mechanism from a flaw in a pre-cracked rock under compression显示文摘In many situations rocks are subjected to biaxial loading and the failure process is controlled by the lateral confinement stresses. The importance of confinement stresses has been recognized in the literature by many researchers, in particular, its influence on strength and on the angle of fracture, but still there is not a clear description for the influence of confining stress on the crack propagation mechanism of rocks. This paper presents a numerical procedure for the analysis of crack propagation in rock-like materials under compressive biaxial loads. Several numerical simulations of biaxial tests on the rock specimen have been carried out by a bonded particle model (BPM) and the influence of confinement on the mechanism of crack propagation from a single flaw in rock specimens is studied. For this purpose, several biaxial compressive tests on rectangular specimens under different confinement stresses were modeled in (2 dimensional particle flow code) PFC 2D . The results show that wing cracks initiate perpendicular to the flaw and trend toward the direction of major stress, however, when the lateral stresses increase, this initiation angle gets wider. Also it is concluded that in addition to the material type, the initiation direction of the secondary cracks depends on confinement stresses, too. Besides, it is understood that secondary cracks may be produced from both tensile and shear mechanisms. | Amin Manouchehrian Mohammad Fatehi Marji | 2012 | Acta Mechanica Sinica2012，28，5： | 9 |
| 3 | Simulation of crack coalescence mechanism underneath single and double disc cutters by higher order displacement discontinuity method显示文摘The present research is focused on the numerical crack coalescence analysis of the micro-cracks and cracks produced during the cutting action of TBM disc cutters. The linear elastic fracture mechanics(LEFM) concepts and the maximum tangential stress criterion are used to investigate the micro crack propagation and its direction underneath the excavating discs. A higher order displacement discontinuity method with quadratic displacement discontinuity elements is used to estimate the stress intensity factors near the crack tips. Rock cutting mechanisms under single and double type discs are simulated by the proposed numerical method.The main purposes of the present modeling are to simulate the chip formation process of indented rocks by single and double discs.The effects of specific disc parameters(except speed) on the thrust force Ft, the rolling force Fr, and the specific energy ES are investigated. It has been shown that the specific energy(energy required to cut through a unit volume of rock) of the double disc is less than that of the single disc. Crack propagation in rocks under disc cutters is numerically modeled and the optimum ratio of disc spacing S to penetration depth Pd(i.e. S/Pd ratio) of about 10 is obtained, which is in good agreement with the theoretical and experimental results cited in the literature. | Mohammad Fatehi Marji | 2015 | Journal of Central South University2015，22，3： | 4 |
| 4 | Experimental and numerical study of crack propagation and coalescence in pre-cracked rock-like disks显示文摘 | Hadi Haeri Kourosh Shahriar Mohammad Fatehi Marji Parviz Moarefvand | 2014 | International Journal of Rock Mechanics and Mining Sciences2014，，： | 2 |
| 5 | Fracture analyses of different pre-holed concrete specimens under compression显示文摘Crack propagation processes in specially prepared concrete discs and rectangular specimens containing a single cylindrical hole or multiple holes of varying diameters have been studied both experimentally and numerically.In this research, the cracks coalescence paths in Brazilian disc and rectangular specimens made from rock-like material containing multi-holes are investigated. These concrete specimens are specially prepared from an appropriate mixture of Portland Pozzolana Cement(PPC), fine sands, and water.The pre-holed Brazilian discs and rectangular specimens are experimentally tested under compression. The breakage load in the ring type disc specimens containing an axial hole with varying diameters is measured and the distribution of the induced lateral stress is obtained. The mechanism of cracks propagation in the wall of the ring type specimens is also studied. In the case of multi-hole Brazilian disc and rectangular specimens, the cracks propagation and cracks coalescence are also investigated. These experiments are numerically modeled by a modified higher order displacement discontinuity method. It has been shown that the corresponding experimental and numerical results are in good agreement with each other. The results presented in this research validate the accuracy and applicability of these crack analyses procedures. | Hadi Haeri Alireza Khaloo Mohammad Fatehi Marji | 2015 | Acta Mechanica Sinica2015，31，6： | 2 |
| 6 | Experimental and Numerical Study of Shear Fracture in Brittle Materials with Interference of Initial Double Cracks显示文摘A simultaneous experimental and numerical study of shear fracture of concrete-like materials is carried out using Brazilian disc specimens with initial double edge cracks and fourpoint bending beam specimens with double edge-notches.The interference effects of two cracks/notches are investigated through varied ligament angles and crack lengths.It is shown that shear fracturing paths change remarkably with the initial ligament angles and crack lengths.The cracked specimens are numerically simulated by an indirect boundary element method.A comparison between the numerical results and the experimental ones shows good agreement. | Hadi Haeri Vahab Sarfarazi Mohammad Fatehi Marji Ahmadreza Hedayat Zheming Zhu | 2016 | Acta Mechanica Solida Sinica2016，29，5： | 2 |
| 7 | DEM simulation of confining pressure effects on crack opening displacement in hydraulic fracturing显示文摘Hydraulic fracture is one of the key methods in well stimulation to increase production of oil and gas.Crack Opening Displacement(COD) is of great importance in this method since it is in direct relation with permeability and production rate.In 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 solution.Numerical 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 equation.The proposed equation considers the effect of confining pressure and its results are in good agreement with numerical results. | Abdollahipour Abolfazl Fatehi Marji Mohammad Yarahmadi Bafghi Alireza Gholamnejad Javad | 2016 | International Journal of Mining Science and Technology2016，26，4： | 2 |
| 8 | The effectiveness of 17α-hydroxyprogesterone caproate in obese women for prevention of preterm delivery显示文摘 | Ngai I Marji M Nero N | 2014 | Obstet Gynecol2014，1231，： | 1 |
| 9 | A New Algorithm for Dominant Points Detection and Polygonization of Digital Curves显示文摘 | Marji M Sly P | 2003 | Pattern Recognition2003，36，10： | 1 |
| 10 | A hybridized numerical and regression method for estimating the minimum rock pillar width of twin circular tunnels显示文摘 | SIAHMANSOURI A GHOLAMNEJAD J MARJI M F | 2014 | Arabian Journal of Geosciences2014，7，5： | 1 |
| 11 | Unmet Need and Problems Accessing Specialty Medical and Related Services Among Children with Special Health Care Needs显示文摘 | Marji Erickson Warfield Stephen Gulley | 2006 | Maternal and Child Health Journal2006，，2： | 1 |
| 12 | Multivariate analysis of microarray data by principal component discriminant analysis : prioritizing relevant transcripts linked to the degradation of different carbohydrates in Pseudomonas putida S12 显示文摘 | MARJI~T J VAN DER W PIETERSE B VAN LUIJK N | 2006 | Microbiology2006，152，： | 1 |
| 13 | A bondedparticle model for analysis of the flaw orientation effect oncrack propagation mechanism in brittle materials undercompression 显示文摘 | Manouchehrian A Sharifzadeh M Marji M F | 2014 | Archives o f Civil and MechanicalEngineering2014，4，1： | 1 |
| 14 | Numerical analysis of quasi-static crack branching in brittle solids by a modified displacement discontinuity method显示文摘 | Mohammad Fatehi Marji | 2013 | International Journal of Solids and Structures2013，，： | 1 |
| 15 | A Bonded Particle Model for Analysis of the Flaw Orientation Effect on Crack Propagation Mechanism in Brittle Materials under Compression 显示文摘 | Manouchehrian A Sharifzadeh M Marji M F | 2014 | Archives of Civil and Mechanical Engineering2014，14，1： | 1 |
| 16 | Comparison of indirect boundary element and finite element methods A case study:Shiraz-Esfahan railway tunnel in Iran显示文摘Because of the high importance of transportation tunnels,most precise analyses of stress concentration and displacement around them are essential to provide safety of them as much as possible.Recently,various numerical methods such as finite element method(FEM),discrete element method(DEM),finite difference method(FDM)and boundary element method(BEM)have been used extremely in geosciences problems,but among these numerical methods,BEM has been used less than others because the computational algorithm is not so straightforward.This paper suggests the implementation of the indirect boundary element method(IBEM)as a formulation of BEM to analyze displacement around Shiraz-Esfahan railway tunnel in Zagros Mountains southwest of Iran.For this purpose,this tunnel has been modeled numerically using two-dimensional fictitious stress method(TWOFS)algorithm.To validate the results,they were compared with FEM results as a commonly used numerical method.Results of current theoretical study have shown that the presented approach using IBEM is reasonably accurate and can be used for analysis of displacement in geosciences problems.In rock mechanics,for problems with a low ratio of boundary surface to volume,FEM is not very well suited and may be cumbersome,but use of such a proposed IBEM approach can be particularly attractive. | Amin MANOUCHEHRIAN Mohammad Fatehi MARJI Mohsen MOHEBBI | 2012 | Frontiers of Structural and Civil Engineering2012，6，4： | 1 |
| 17 | Use of biologic agents in pediatric psoriasis显示文摘 | Marji JS Marcus R Moennich J | 2010 | J Drugs Dermatol2010，9，8： | 1 |
| 18 | On the accuracy of higher order displacement discontinuity method(HODDM) in the solution of linear elastic fracture mechanics problems显示文摘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. | Abolfazl Abdollahipour Mohammad Fatehi Marji Alireza Yarahmadi Bafghi Javad Gholamnejad | 2016 | Journal of Central South University2016，23，11： | 1 |
| 19 | A new algorithm for dominant points detectionand polygonization of digital curves显示文摘 | Marji M Siy P | 2003 | Pattern Recognition2003，，： | 1 |
| 20 | A new algorithm for dominant points detection and polygonization of digital curves显示文摘 | Marji M Siy P | 2003 | Pattern Recognition2003，36，10： | 1 |
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