Finite Element Analysis of the Influence of Artificial Cementation on the Strength Parameters and Bearing Capacity of Sandy Soil under a Strip Footing

Artificial cementation is a method commonly used to enhance and improve soil properties. This paper investigates the effect of using different amounts of cement on soil strength parameters and soil bearing capacity, using the finite element method. Experimental tests are conducted on soil samples with different amounts of Portland cement. A 2-D numerical model is created and validated using the numerical modelling software, COMSOL Multiphysics 5.6 software. The study finds that the cohesion, and the angle of the internal friction of the soil samples increase significantly as a result of adding 1%, 2%, and 4% of Portland cement. The results demonstrate that the stresses and strain under the strip footing proposed decrease by 3.24% and 7.42%. Moreover, the maximum displacement also decreases by 1.47% and 2.97%, as a result of adding cements of 2% and 4%. The bearing capacity values obtained are therefore excellent, especially when using the 2% and 4% cement. The increase identified is due to the increased values of the bearing capacity factors. It is concluded that from an economic viewpoint, using 2% cement is the best option.

Mesomechanics Finite-element Method for Determining the Shear Strength of Mudded Intercalation Materials

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.

APPLICATION OF STOCHASTIC FINITE ELEMENT METHOD TO STRENGTH AND STABILITY ANALYSIS OF EARTH DAMS

This paper applies the stochastic finite element method to analyse the statistics of stresses in earth dams and assess the safety and reliability of the dams. Formulations of the stochastic finite element method are briefly reviewed and the procedure for assessing dam's strength and stability is described. As an example, a detailed analysis for an actual dam Nululin dam is performed. A practical method for studying built-dams based on the prototype observation data is described.

Strength reduction and step-loading finite element approaches in geotechnical engineering

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.

New method of designing anti-slide piles——the strength reduction FEM

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.

Analysis of Biomechanical Behaviour of Anterior Teeth Using Two Different Methods: Finite Element Method and Experimental Tests

The main objective of this study was to compare the results obtained with both virtual and experimental research methods, when the biomechanical behavior of teeth restored with esthetic posts was investigated. The finite element method was used to develop models of healthy maxillary canines and maxillary canines restored with definitive crowns and glass-fiber posts, quartzfiber posts, and titanium posts. Stress distribution was observed when external loads were applied. Load was applied in-vitro to analyse the fracture resistance of 48 maxillary canines restored in the same way as it was considered in the virtual method. The analysis of results using the finite element method led to the conclusion that restored teeth, in which the elastic modulus of the post was similar to that of the dentine and the material of the core had the best biomechanical performance. The experimental study validated the virtual analysis.

A Finite Element Analysis on Static Strength of a Complex Section

A static finite element analysis (FEA) of an impulsive controller section is presented. The boundary condition and a part of the loads are applied. Considering the grades of the stress around the holes being large, the dense grids are adjusted accordingly. Four cases with different loads are compared, thus the influences of different loads on the section are analyzed. Numerical results show that the maximum stress of the section is lower than the strength limit of the material, and the section will not be broken with the static loads.

Modeling Technology in Finite Element Analysis of Electrostatic Proximity Fuze Problem

In order to analyze the electrostatic field concerned with electrostatic proximity fuze problem using the available finite analysis software package, the technology to model the problem with a scale reduction object and boundary was presented. The boundary is determined by the maximum distance the sensor can detect. The object model is obtained by multiplying the terms in Poisson's equation with a scale reduction factor and the real value can be reconstructed with the same reverse process after software calculation. Using the finite element analysis program, the simulation value is close to the theoretical value with a little error. The boundary determination and scale reduction method is suitable to modeling the irregular electrostatic field around air targets, such as airplane, missile and so on, which is based on commonly used personal computer (PC). The technology reduces the calculation and storage cost greatly.

Finite element analyses of slope stability problems using non-associated plasticity

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.

Relations of Microstructural Attributes and Strength-Ductility of Zirconium Alloys with Hydrides

As the first safety barrier of nuclear reactors,zirconium alloy cladding tubes have attracted extensive attention because of its good mechanical properties.The strength and ductility of zirconium alloy are of great significance to the service process of cladding tubes,while brittle hydrides precipitate and thus deteriorate the overall performance.Based on the cohesive finite element method,the effects of cohesive strength,interfacial characteristics,and hydrides geometric characteristics on the strength and ductility of two-phase material(zirconium alloy with hydrides)are numerically simulated.The results show that the fracture behavior is significantly affected by the cohesive strength and that the overall strength and ductility are sensitive to the cohesive strength of the zirconium alloy.Furthermore,the interface is revealed to have prominent effects on the overall fracture behavior.When the cohesive strength and fracture energy of the interface are higher than those of the hydride phase,fracture initiates in the hydrides,which is consistent with the experimental phenomena.In addition,it is found that the number density and arrangement of hydrides play important roles in the overall strength and ductility.Our simulation provides theoretical support for the performance analysis of hydrogenated zirconium alloys during nuclear reactor operation.

Finite element analysis of slope stability by expanding the mobilized principal stress Mohr's circles-Development, encoding and validation

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.

Physics-based seismic analysis of ancient wood structure:fault-to-structure simulation

Based on the domain reduction method,this study employs an SEM-FEM hybrid workflow which integrates the advantages of the spectral element method(SEM)for flexible and highly efficient simulation of seismic wave propagation in a three-dimensional(3D)regional-scale geophysics model and the finite element method(FEM)for fine simulation of structural response including soil-structure interaction,and performs a physics-based simulation from initial fault rupture on an ancient wood structure.After verification of the hybrid workflow,a large-scale model of an ancient wood structure in the Beijing area,The Tower of Buddhist Incense,is established and its responses under the 1665 Tongxian earthquake and the 1730 Yiheyuan earthquake are simulated.The results from the simulated ground motion and seismic response of the wood structure under the two earthquakes demonstrate that this hybrid workflow can be employed to efficiently provide insight into the relationships between geophysical parameters and the structural response,and is of great significance toward accurate input for seismic simulation of structures under specific site and fault conditions.

Formation of internal cracks during soft reduction in rectangular bloom continuous casting

To investigate the formation of internal cracks in GCrl 5 bearing steels during the soft reduction process in rectangular bloom con- tinuous casting, fully coupled thermomechanieal finite element models were developed using the commercial software MSC.MARC, and microstructures and fractographs were also observed. With the finite element models, the contours of temperature, equivalent plastic strain, and equivalent vun Mises stress were simulated. It is observed that the fracture surfaces of internal cracks are covered by cleavage or quasi-cleavage facets. The region of internal cracks in the intergranular brittle fracture mode is in the mushy zone between the zero ductility temperature （ZDT） and the zero strength temperature （ZST）. The simulated equivalent plastic strain in the crack region is 2.34%-2.45%, which is larger than the critical strain （0.4%-1.5%）, and the equivalent von Mises stress is 1.84-5.05 MPa, which is within the range of criti- cal stress （3.9-7.2 MPa）, thus resulting in the occurrence of internal cracks. Reducing the soft reduction amount from 3 to 2 mm can lower the stress under the critical value.

3D FEM analysis for layered rock considering anisotropy of shear strength

An empirical expression of cohesion （C） and friction angle （Ф） 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 Ф 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 （p） of shear failure plane （or weakest shear plane） with respect to the major principal stress as well as the corresponding C and Ф 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.

Structural Strength Analysis of a Tri-Floater Floating Foundation for Offshore VAWT

Vertical axis wind turbines(VAWTs) are advantageous for the development of large-scale offshore wind power because the drive system is located at the bottom of the turbine. This study investigates the structural strength of a tri-floater floating foundation supporting a 2.6 MW Darrieus VAWT. Finite element models of the floating foundation were developed using space plate-beam elements. The environmental loads, such as the aerodynamic loads, static wind loads, and wave-current loads, were considered. The general strengths of the floating foundation were calculated for the normal operating case(a cut-out wind speed of 25 m s^(-1) and blade rotation of 12 r min^(-1) were used to analyze the most unfavorable loads) and an extreme case(wind speed of 40 m s^(-1) and parked blades), and the weak components of the structure were analyzed. The results show that the floating foundation meets the strength requirements and the structural stress is highest when the wave, wind, and current are in a collinear direction. The main and secondary supporting bars transmit the loads between the stand columns and the tower foundation, and their stresses are higher than those in the other components. In the actual design, these supporting bars should be strengthened. The aerodynamic loads are very important and should be considered in the structural strength analysis of the floating foundation and the floating wind turbine system.

Characteristics of Deformation and Strength of Concrete in Plane Strain State

The characteristics of deformation and strength of concrete under the plane strain condition are studied experimentally with the triaxial apparatus designed by the authors and are compared with those under the plane stress condition. A formula of stress transformation between plane stress and plane strain conditions is proposed for the elasto-plastic state, and it provides a theoretical basis for simplifying nonlinear analysis and fully using the strength of concrete.

Influences of Randomly Distributed Wall Thickness of Beverage Can on Its Strength and Stiffness

This paper describes the research undertaken on the strength and stiffness of fluctuation on the wall thickness of steel beverage cans using the Monte Carlo stochastic finite element method. Sample distributions were firstly assumed and then proven using the data observations of the wall thickness, the APDL language was then applied, and the stresses and displacements of the can were calculated by using the ANSYS software. It is concluded that the structural reliability of a steel making beverage can be estimated accurately.

Resistance optimization of flexes in aluminum reduction cells

The resistance arrangements of the flexes connecting with the cathode bus bar in aluminum reduction cells were generalized as three modes. In each mode the universal method to select proper resistivity of the flexes was induced respectively to insure that the current in local group of flexes was equal. Furthermore, a 350 kA aluminum reduction cell based electric field model was developed by finite element method to evaluate the effect of the method. Suggestions on selection of three modes were also put forward. The results show that the methods of resistance optimization can reduce the current variation about 180 A compared with that in original case.

Numerical calculation of thermal field and heat transfer coefficient for 160 kA aluminum reduction cell

The principle of thermal flux being constant in heat flow tube and the principle of heat balance were applied to analyze and calculate the steady state thermal field and the electrolyte ledge heat transfer coefficient of aluminum reduction cell by finite element method. The calculated results show that the melt ledge heat transfer coefficient in the 160kA prebaked anode aluminum reduction cell of Guizhou Aluminum Smelter is higher than that of other cells of the same current. It is also found that the electrolyte and metal flow much faster, which may be the results of poor bus bar arrangements. Meanwhile, the calculated results of melt ledge heat transfer coefficient by heat flow tube method are almost in full agreement with the former works. This verifies the applicability of this method.

The Influence of the Inclusion on the Fatigue Strength of Ceramic Bush

In traditional plain bearing, bushes are made of metal. In order to improve the properties of the bush, it is necessary to conduct an experiment in which the purpose is to replace metal with ceramic. Because of its high hardness, long fatigue wear life, excellent corrosion resistance, good self-lubricating and low density, ceramic bush is suitable for plain bearing. In this paper the influence of the inclusion on the fatigue wear strength of the bush are analysed under the action of a external load with the finite element method. All these work may provide proofs for analysing the wearing mechanism and for controlling the effect of the inclusion. When the normal outer load is 6 N/mm, namely P=6 N/mm. The compressive main stress will be formed inside the basic part of the bush, which gathers in the center touching area between the journal and the the bush around the inclusion, most of the units have their own maximum alternate stress σ max, which is smaller than the fatigue limit of the material of bushes σ 0 (σ 0=60 MPa). If there is P=30 N/mm, some units will have σ max approaching the fatigue limit, stress concentration will occur around the inclusion, so will the local plastic deformation. Some special units exceed the fatigue limit of the material. When P=225 N/mm,most of the units will have the σ max, about 50～300 MPa, which surpasses the fatigue limit. At this time micro pitting and cracking on the bush surface can be observed with SEM. When P=350 MPa, the σ max is about 300～900 MPa, the center touching area on the surface of the sample and the units around the inclusion will exceed the fatigue limit generally, the surface of the bush, the serious wear corrosion and big fatigue cracking can be observed.