The finite element limit analysis method has the advantages of both numerical and traditional limit equilibrium techniques and it is particularly useful to geotechnical engineering.This method has been developed in Ch...The finite element limit analysis method has the advantages of both numerical and traditional limit equilibrium techniques and it is particularly useful to geotechnical engineering.This method has been developed in China,following well-accepted international procedures,to enhance understanding of stability issues in a number of geotechnical settings.Great advancements have been made in basic theory,the improvement of computational precision,and the broadening of practical applications.This paper presents the results of research on(1) the efficient design of embedded anti-slide piles,(2) the stability analysis of reservoir slopes with strength reduction theory,and(3) the determination of the ultimate bearing capacity of foundations using step-loading FEM(overloading).These three applications are evidence of the design improvements and benefits made possible in geotechnical engineering by finite element modeling.展开更多
A new method regarding mesomechanics finite-element research is proposed to predict the peak shear strength of mudded intercalation materials on a mesoscopic scale. Based on geometric and mechanical parameters, along ...A new method regarding mesomechanics finite-element research is proposed to predict the peak shear strength of mudded intercalation materials on a mesoscopic scale. Based on geometric and mechanical parameters, along with the strain failure criteria obtained by sample's deformation characteristics, uniaxial compression tests on the sample were simulated through a finite-element model, which yielded values consistent with the data from the laboratory uniaxial compression tests, implying that the method is reasonable. Based on this model, a shear test was performed to calculate the peak shear strength of the mudded intercalation, consistent with values reported in the literature, thereby providing a new approach for investigating the mechanical properties of mudded intercalation materials.展开更多
At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be...At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.展开更多
In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechan...In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechanism a priori and enable the determination of the safety level more accurately. The paper compares the performances of strength reduction finite element analysis(SRFEA) with finite element limit analysis(FELA), whereby the focus is related to non-associated plasticity. Displacement-based finite element analyses using a strength reduction technique suffer from numerical instabilities when using non-associated plasticity, especially when dealing with high friction angles but moderate dilatancy angles. The FELA on the other hand provides rigorous upper and lower bounds of the factor of safety(FoS) but is restricted to associated flow rules. Suggestions to overcome this problem, proposed by Davis(1968), lead to conservative FoSs; therefore, an enhanced procedure has been investigated. When using the modified approach, both the SRFEA and the FELA provide very similar results. Further studies highlight the advantages of using an adaptive mesh refinement to determine FoSs. Additionally, it is shown that the initial stress field does not affect the FoS when using a Mohr-Coulomb failure criterion.展开更多
In recent years,finite element analysis is increasingly being proposed in slope stability problems as a competitive method to traditional limit equilibrium methods(LEMs)which are known for their inherent deficiencies....In recent years,finite element analysis is increasingly being proposed in slope stability problems as a competitive method to traditional limit equilibrium methods(LEMs)which are known for their inherent deficiencies.However,the application of finite element method(FEM)to slope stability as a strength reduction method(SRM)or as finite element limit analysis(FELA)is not always a success for the drawbacks that characterize both methods.To increase the performance of finite element analysis in this problem,a new approach is proposed in this paper.It consists in gradually expanding the mobilized stress Mohr’s circles until the soil failure occurs according to a prescribed non-convergence criterion.The present approach called stress deviator increasing method(SDIM)is considered rigorous for three main reasons.Firstly,it preserves the definition of the factor of safety(FOS)as the ratio of soil shear strength to the mobilized shear stress.Secondly,it maintains the progressive development of shear stress resulting from the increase in the principal stress deviator on the same plane,on which the shear strength takes place.Thirdly,by introducing the concept of equivalent stress loading,the resulting trial stresses are checked against the violation of the actual yield criterion formed with the real strength parameters rather than those reduced by a trial factor.The new numerical procedure was encoded in a Fortran computer code called S^(4)DINA and verified by several examples.Comparisons with other numerical methods such as the SRM,gravity increasing method(GIM)or even FELA by assessing both the FOS and contours of equivalent plastic strains showed promising results.展开更多
An empirical expression of cohesion(C) and friction angle(φ) for layered rock was suggested.This expression was compared with a test result made by the former researchers.The constitutive relationship of a transverse...An empirical expression of cohesion(C) and friction angle(φ) for layered rock was suggested.This expression was compared with a test result made by the former researchers.The constitutive relationship of a transversely isotropic medium and Mohr-Coulomb criterion in which C and φ vary with directions were employed,and a relative 3D elasto-plastic FEM code was developed,in which the important thing was to adopt a search-trial method to find the orientation angle(ρ) of shear failure plane(or weakest shear plane) with respect to the major principal stress as well as the corresponding C and φ.Taking an underground opening as the calculation object,the numerical analyses were carried out by using the FEM code for two cases of transversely isotropic rock and isotropic rock,respectively,and the computation results were compared.The results show that when the rock is a transversely isotropic one,the distributions of displacements,plastic zones and stress contours in the surrounding rock will be non-axisymmetric along the tunnel's vertical axis,which is very different from that of isotropic rock.The stability of the tunnel in transversely isotropic rock is relatively low.展开更多
Single-fiber pull-out testing(SFPOT)methods are frequently used to evaluate the inter-facial adhesion between fiber and matrix in composite materials.To make such pull-out mea-surements,however,the length of embedded ...Single-fiber pull-out testing(SFPOT)methods are frequently used to evaluate the inter-facial adhesion between fiber and matrix in composite materials.To make such pull-out mea-surements,however,the length of embedded fiber must be small enough so that the fiberdoes not break before it is pulled freely.This is difficult to achieve by conventional methodswith fibers of small diameter,such as the carbon fibers.In this paper,a fiber pull-out ex-periment is described.Specialized apparatus in our laboratory,as well as this technique forsample preparation are discussed in detail.The interracial shear strength of carbon fiber/resin matrix composites is analyzed quantitatively by using the finite-element method.TheSFPOT system has been proved to be an available means for the study of interracial proper-ties for carbon fiber/resin matrix composites.展开更多
A two-dimensional finite element method (FEM) model that incorporates faults,elastic rock physical properties,topographical load due to gravity and far-field plate velocity boundary conditions was used to recognize th...A two-dimensional finite element method (FEM) model that incorporates faults,elastic rock physical properties,topographical load due to gravity and far-field plate velocity boundary conditions was used to recognize the seismogenic stress state along the fold-and-thrust belt of the Precordillera-Sierras Pampeanas ranges of western Argentina. A plane strain model with nine experiments was presented here to examine the fault strength with two major rock phyical properties:cohesion and angle of internal friction. Mohr-Coulomb failure criterion with bulk rock properties were applied to analyse faults. The stress field at any point of the model was assumed to be comprised of gravitational and tectonic components. The analysis was focused to recognize the seismogenic shear strain concentrated in the internal-cristaline domain of the orogene shown by the modeling. Modeling results are presented in terms of four parameters,i. e.,(i) distributions,orientations,and magnitudes of principal stresses (σ1 and σ3),(ii) displacement vector,(iii) strain distribution,and (iv) maximum shear stress (τmax) contour line within the model. The simulation results show that the compressive stress is distributed in and around the fault systems. The overall orientation of σ1 is in horizontal directions,although some stress reorientations do occur within weaker parts,especially subsequent to the faults. A large-scale shear stress is accumulating along the active faults of Tapias-Villicum Fault (TVF),Salinas-Berros Fault (SBF),Ampacama-Niquizanga Fault (ANF) and Las Charas Fault (CF),which could act as local stress and strain modulators to localize the earthquakes occurrence.展开更多
基金Supported by the National Natural Science Foundation of China (40318002)
文摘The finite element limit analysis method has the advantages of both numerical and traditional limit equilibrium techniques and it is particularly useful to geotechnical engineering.This method has been developed in China,following well-accepted international procedures,to enhance understanding of stability issues in a number of geotechnical settings.Great advancements have been made in basic theory,the improvement of computational precision,and the broadening of practical applications.This paper presents the results of research on(1) the efficient design of embedded anti-slide piles,(2) the stability analysis of reservoir slopes with strength reduction theory,and(3) the determination of the ultimate bearing capacity of foundations using step-loading FEM(overloading).These three applications are evidence of the design improvements and benefits made possible in geotechnical engineering by finite element modeling.
基金Funded by the National Natural Science Foundation of China(No.51574201)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection(Chengdu University of Technology)(KLGP2015K006)the Scientific and Technical Youth Innovation Group(Southwest Petroleum University)(2015CXTD05)
文摘A new method regarding mesomechanics finite-element research is proposed to predict the peak shear strength of mudded intercalation materials on a mesoscopic scale. Based on geometric and mechanical parameters, along with the strain failure criteria obtained by sample's deformation characteristics, uniaxial compression tests on the sample were simulated through a finite-element model, which yielded values consistent with the data from the laboratory uniaxial compression tests, implying that the method is reasonable. Based on this model, a shear test was performed to calculate the peak shear strength of the mudded intercalation, consistent with values reported in the literature, thereby providing a new approach for investigating the mechanical properties of mudded intercalation materials.
基金This research was funded by the National Natural Science Foundation of China (Grant No.40872191)NSF of Chongqing(Grant No. CSTC2009BB6178)
文摘At present,the thrust of an anti-slide pile can be worked out with some calculation methods. However,the resistance in front of the pile,the distributions of resistance and thrust,and appropriate pile length cannot be easily obtained. In this paper,the authors applied the strength-reduction finite element method (FEM) to several design cases of anti-slide piles. Using this method,it is possible to take the pile-soil interactions into consideration,obtain reasonable resistance in front of pile and the distributions of thrust and resistance,and reasonable lengths of anti-slide piles. In particular,the thrust and resistance imposed on embedded anti-slide piles can be calculated and composite anti-slide pile structures such as anchored piles and braced piles can be optimized. It is proved through the calculation examples that this method is more reliable and economical in the design of anti-slide pile.
文摘In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechanism a priori and enable the determination of the safety level more accurately. The paper compares the performances of strength reduction finite element analysis(SRFEA) with finite element limit analysis(FELA), whereby the focus is related to non-associated plasticity. Displacement-based finite element analyses using a strength reduction technique suffer from numerical instabilities when using non-associated plasticity, especially when dealing with high friction angles but moderate dilatancy angles. The FELA on the other hand provides rigorous upper and lower bounds of the factor of safety(FoS) but is restricted to associated flow rules. Suggestions to overcome this problem, proposed by Davis(1968), lead to conservative FoSs; therefore, an enhanced procedure has been investigated. When using the modified approach, both the SRFEA and the FELA provide very similar results. Further studies highlight the advantages of using an adaptive mesh refinement to determine FoSs. Additionally, it is shown that the initial stress field does not affect the FoS when using a Mohr-Coulomb failure criterion.
文摘In recent years,finite element analysis is increasingly being proposed in slope stability problems as a competitive method to traditional limit equilibrium methods(LEMs)which are known for their inherent deficiencies.However,the application of finite element method(FEM)to slope stability as a strength reduction method(SRM)or as finite element limit analysis(FELA)is not always a success for the drawbacks that characterize both methods.To increase the performance of finite element analysis in this problem,a new approach is proposed in this paper.It consists in gradually expanding the mobilized stress Mohr’s circles until the soil failure occurs according to a prescribed non-convergence criterion.The present approach called stress deviator increasing method(SDIM)is considered rigorous for three main reasons.Firstly,it preserves the definition of the factor of safety(FOS)as the ratio of soil shear strength to the mobilized shear stress.Secondly,it maintains the progressive development of shear stress resulting from the increase in the principal stress deviator on the same plane,on which the shear strength takes place.Thirdly,by introducing the concept of equivalent stress loading,the resulting trial stresses are checked against the violation of the actual yield criterion formed with the real strength parameters rather than those reduced by a trial factor.The new numerical procedure was encoded in a Fortran computer code called S^(4)DINA and verified by several examples.Comparisons with other numerical methods such as the SRM,gravity increasing method(GIM)or even FELA by assessing both the FOS and contours of equivalent plastic strains showed promising results.
基金Project(2010CB732101) supported by the National Basic Research Program of China Project(51079145) supported by the National Natural Science Foundation of China
文摘An empirical expression of cohesion(C) and friction angle(φ) for layered rock was suggested.This expression was compared with a test result made by the former researchers.The constitutive relationship of a transversely isotropic medium and Mohr-Coulomb criterion in which C and φ vary with directions were employed,and a relative 3D elasto-plastic FEM code was developed,in which the important thing was to adopt a search-trial method to find the orientation angle(ρ) of shear failure plane(or weakest shear plane) with respect to the major principal stress as well as the corresponding C and φ.Taking an underground opening as the calculation object,the numerical analyses were carried out by using the FEM code for two cases of transversely isotropic rock and isotropic rock,respectively,and the computation results were compared.The results show that when the rock is a transversely isotropic one,the distributions of displacements,plastic zones and stress contours in the surrounding rock will be non-axisymmetric along the tunnel's vertical axis,which is very different from that of isotropic rock.The stability of the tunnel in transversely isotropic rock is relatively low.
基金the High Technology Research and Development Programme of China.
文摘Single-fiber pull-out testing(SFPOT)methods are frequently used to evaluate the inter-facial adhesion between fiber and matrix in composite materials.To make such pull-out mea-surements,however,the length of embedded fiber must be small enough so that the fiberdoes not break before it is pulled freely.This is difficult to achieve by conventional methodswith fibers of small diameter,such as the carbon fibers.In this paper,a fiber pull-out ex-periment is described.Specialized apparatus in our laboratory,as well as this technique forsample preparation are discussed in detail.The interracial shear strength of carbon fiber/resin matrix composites is analyzed quantitatively by using the finite-element method.TheSFPOT system has been proved to be an available means for the study of interracial proper-ties for carbon fiber/resin matrix composites.
基金the Ministry of Education, Culture, Sports, Science and Technology (Monbukagakusho) of Japan for its financial support of this research.
文摘A two-dimensional finite element method (FEM) model that incorporates faults,elastic rock physical properties,topographical load due to gravity and far-field plate velocity boundary conditions was used to recognize the seismogenic stress state along the fold-and-thrust belt of the Precordillera-Sierras Pampeanas ranges of western Argentina. A plane strain model with nine experiments was presented here to examine the fault strength with two major rock phyical properties:cohesion and angle of internal friction. Mohr-Coulomb failure criterion with bulk rock properties were applied to analyse faults. The stress field at any point of the model was assumed to be comprised of gravitational and tectonic components. The analysis was focused to recognize the seismogenic shear strain concentrated in the internal-cristaline domain of the orogene shown by the modeling. Modeling results are presented in terms of four parameters,i. e.,(i) distributions,orientations,and magnitudes of principal stresses (σ1 and σ3),(ii) displacement vector,(iii) strain distribution,and (iv) maximum shear stress (τmax) contour line within the model. The simulation results show that the compressive stress is distributed in and around the fault systems. The overall orientation of σ1 is in horizontal directions,although some stress reorientations do occur within weaker parts,especially subsequent to the faults. A large-scale shear stress is accumulating along the active faults of Tapias-Villicum Fault (TVF),Salinas-Berros Fault (SBF),Ampacama-Niquizanga Fault (ANF) and Las Charas Fault (CF),which could act as local stress and strain modulators to localize the earthquakes occurrence.