The goal of this research is to develop a robust, continuum-based approach for a three-dimensional, Finite Element Method (FEM) simulation of layered geomaterials. There are two main approaches to the numerical modeling of layered geomaterials; discrete or discontinuous techniques and an equivalent continuum concept. In the discontinuous methodology, joints are explicitly simulated. Naturally, discrete techniques provide a more accurate description of discontinuous materials. However, they are complex and necessitate care in modeling of the interface. Also, in many applications, the definition of the input model becomes impractical as the number of joints becomes large. In order to overcome the difficulties associated with discrete techniques, a continuum-based approach has become popular in some application areas. When using a continuum model, a discrete material is replaced by a homogenized continuous material, also known as an 'equivalent continuum'. This leads to a discretization that is independent of both the orientation and spacing of layer boundaries. However, if the layer thickness (i.e., internal length scale of the problem) is large, the classical continuum approach which neglects the effect of internal characteristic length can introduce large errors into the solution. In this research, a full 3D FEM formulation for the elasto-plastic modeling of layered geomaterials is proposed within the framework of Cosserat theory. The effect of the bending stiffness of the layers is incorporated in the matrix of elastic properties. Also, a multi-surface plasticity model, which allows for plastic deformation of both the interfaces between the layers and intact material, is introduced. The model is verified against analytical solutions, discrete numerical models, and experimental data. It is shown that the FEM Cosserat formulation can achieve the same level of accuracy as discontinuous models in predicting the displacements of a layered material with a periodic microstructure. Furthermore, the method is capable of reproducing the strength behaviour of materials with one or more sets of joints. Finally, due to the incorporation of layer thickness into the constitutive model, the FEM Cosserat formulation is capable of capturing complicated failure mechanisms such as the buckling of individual layers of material which occur in stratified media.

The objective of the present study was to develop a fluid flow-coupled distinct element model capable of capturing the undrained behaviour of granular soils by considering fundamental physical mechanisms that involve fluid flow and particle interaction. The method considers granular media as assemblies of ellipsoidal particles arranged on a plane and interacting by means of contact forces. Saturation effects are incorporated by assuming that particles are immersed in fluid, the flow of which is simulated as occurring through a network of conduits. The flow through conduits is according to a Hagen-Poiseuille relation; a transient solution is obtained by solving a system of differential equations. The developed fluid-flow coupled distinct element was used to conduct various numerical simulations and the mechanisms of undrained deformations were examined from a micromechanical point of view. The dissertation begins with a literature review on the undrained behaviour of granular materials as observed in laboratory experiments. A review of previous attempts to simulate undrained tests micromechanically is also presented, and the advantages and disadvantages of various methods are examined. The capability of the developed model to simulate two-dimensional fluid-flow and pressure dissipation problems is demonstrated by means of comparisons with analytical solutions. Fluid pressure dissipation problems are qualitatively compared with Terzaghi's one-dimension theory of consolidation. It is shown that transient flow problems are accurately modelled by the fluid flow network approach. Simulated compression tests were carried out to examine the effects of different confining pressures and initial densities on the macroscopic response. The results compare favorably with those commonly observed in undrained laboratory experiments. Simulated tests are analyzed from a micromechanical point of view. It is shown that macroscopic behaviour can be traced to changes in micromechanical fabric descriptors. The effects of the interparticle friction angle on the undrained behaviour of the assemblies are investigated. The undrained strength is considerably increased by increasing interparticle friction. The main mechanism found to be responsible for the development of higher strength is the tendency of the specimens to dilate during shear distortion. The effects of the principal stress direction on the macroscopic response are examined. The behaviour of initially anisotropic samples is significantly altered by the direction of the principal stresses relative to the anisotropy direction. It is demonstrated that macroscopic permeability of the media has a considerable effect on the strength. This behaviour is attributed to the inhomogeneity of pore pressure distributions which increases with decreased permeability. The results presented are generally in agreement with observations previously reported from laboratory experiments. The possible applications of the model for future research are also discussed.

A two dimensional continuous numerical model based on Discrete Element Method is used to investigate the behaviour of accretionary wedges with different basal frictions. The models are based on elastic-plastic, brittle material and computational granular dynamics, and several characteristics of the influence of the basal friction are analysed. The model results illustrate that the wedge’s deformation and geometry, for example, fracture geometry, the compression force, area loss, displacement, height and length of the accretionary wedge etc., are strongly influenced by the basal friction. In general, the resulting wedge grows steeper, shorter  and higher, and the compression force is larger when shortened  above a larger friction basement.  Especially, when there is no basal friction, several symmetrical wedges will distribute symmetrically in the domain. The distribution of the internal stress when a new accretionary prime is forming is also studied. The results illustrate that when the stress in a certain zone is larger than a critical number, a new thrust will form there.

The objective of the present study was to develop a fluid flow-coupled distinct element model capable of capturing the undrained behaviour of granular soils by considering fundamental physical mechanisms that involve fluid flow and particle interaction. The method considers granular media as assemblies of ellipsoidal particles arranged on a plane and interacting by means of contact forces. Saturation effects are incorporated by assuming that particles are immersed in fluid, the flow of which is simulated as occurring through a network of conduits. The flow through conduits is according to a Hagen-Poiseuille relation; a transient solution is obtained by solving a system of differential equations. The developed fluid-flow coupled distinct element was used to conduct various numerical simulations and the mechanisms of undrained deformations were examined from a micromechanical point of view. The dissertation begins with a literature review on the undrained behaviour of granular materials as observed in laboratory experiments. A review of previous attempts to simulate undrained tests micromechanically is also presented, and the advantages and disadvantages of various methods are examined. The capability of the developed model to simulate two-dimensional fluid-flow and pressure dissipation problems is demonstrated by means of comparisons with analytical solutions. Fluid pressure dissipation problems are qualitatively compared with Terzaghi's one-dimension theory of consolidation. It is shown that transient flow problems are accurately modelled by the fluid flow network approach. Simulated compression tests were carried out to examine the effects of different confining pressures and initial densities on the macroscopic response. The results compare favorably with those commonly observed in undrained laboratory experiments. Simulated tests are analyzed from a micromechanical point of view. It is shown that macroscopic behaviour can be traced to changes in micromechanical fabric descriptors. The effects of the interparticle friction angle on the undrained behaviour of the assemblies are investigated. The undrained strength is considerably increased by increasing interparticle friction. The main mechanism found to be responsible for the development of higher strength is the tendency of the specimens to dilate during shear distortion. The effects of the principal stress direction on the macroscopic response are examined. The behaviour of initially anisotropic samples is significantly altered by the direction of the principal stresses relative to the anisotropy direction. It is demonstrated that macroscopic permeability of the media has a considerable effect on the strength. This behaviour is attributed to the inhomogeneity of pore pressure distributions which increases with decreased permeability. The results presented are generally in agreement with observations previously reported from laboratory experiments. The possible applications of the model for future research are also discussed.

The general objective of the research effort reported in this thesis was to develop the knowledge required to optimize the design and operation of solid and semi-solid manure handling and land application equipment. Selected physical and rheological properties of manure products deemed to have an influence on the performances of manure handling and land application equipment were measured and general trends were identified among the measured properties. Relationships were also established between the measured properties and the type of manure as well as its total solids concentration. Field experiments were carried out to evaluate the effects of selected mechanical configurations, operating parameters and product properties on the discharge of manure spreaders. The influence of the type of conveying system (scraper conveyor and system of four augers) and the velocity at which it is operated, the geometry of the holding system and the position of a flow-control gate were all included in the analysis. The discharge rates of the machines as well as the specific energy required by the unloading operations were measured. A numerical modeling method called discrete element method (DEM) was used to create virtual manure, a numerical model of the real product. The measured physical and flow properties were used to develop and validate the virtual manure models. It was found that manure products could successfully be represented in a DE framework and that several parameters defining the contact constitutive model in the DEM had an influence on the behaviour of the virtual products. The DEM was then used to study machine-product interactions taking place in handling and land application equipment. Results from field experiments carried out using various land application equipment were used in the development and validation of the interaction models. The predicted flow rates and power requirements were in good agreement with measured data. The results obtained allowed for a better understanding of the flow of manure products in manure handling and land application equipment. It was found that the constitutive model used for the product influenced the results of the machine-product interactions models. A precision banded applicator under development at the University of Saskatchewan was also modeled. The discharge rate of this equipment is influenced by a number of parameters. The predicted mass distribution across the width of the banded applicator was well correlated to the experimental results. The models developed in this thesis have the potential to become powerful engineering tools for the design of improved machines for the handling and land application of solid and semi-solid manure.

A discrete element model (DEM) capable of reproducing the mechanistic behavior of a triaxial compressive test performed on a Vosges sandstone specimen is presented considering similar experimental testing conditions and densely packed spherical elements with low lock-in stress. The main aim of this paper is to illustrate the calibration process of the model‟s micro-parameters when obtained from the experimental meso-parameters measured in the lab. For this purpose, a probabilistic inverse method is introduced to fully define the micro-parameters of the particle models through a joint probability density function, which is conditioned on the experimental observations obtained during a series of tests performed at the L3S-R France. The DEM captures successfully some of the rock mechanical behavior features, including the global stress-strain and failure mechanisms. Results include a detailed parametric analysis consisting of varying each DEM parameter at the time and measuring the model response on the strain-stress domain. First order statistics on probabilistic results show the adequacy of the model to capture the experimental data, including a measure of the DEM performance for different parameter combinations. Also, joint probability density functions and cross-correlations among the micro-parameters are presented.

In the past, most research on soil mechanical properties was carried out for cohesionless soils in the fields of civil and geotechnical engineering. Little research has been carried out for mechanical properties of agricultural soil, which are essential for designing soil engaging tools in agriculture. In this study, unconsolidated undrained triaxial compression tests were performed to study the effects of moisture level and confining pressure on a sandy loam soil. The soil specimens tested had three moisture levels, and they were high (27-29% d.b.), medium (19-21% d.b.) and low (9-11% d.b.). The confining pressures used for the triaxial tests were 50, 100, and 150 kPa. Soil specimen was loaded at a strain rate of 1%/min. Measurements from the tests included stress-strain curve, shear strength, Young’s modulus, Poisson’s ratio, angle of internal friction, and cohesion. A model was developed using the Discrete Element Method (DEM) and computed by Particle Flow Code in three dimensions (PFC3D), a common DEM software. The model simulated the triaxial compression tests, and the model specimen was an assembly of 5-mm spherical particles which were defined by a set of micro parameters. During simulations, soil shear strength was monitored under different confining pressures. Through sensitivity analysis, it was found that most of the micro parameters affected the simulated soil shear strengths and the stress-strain behaviours. The most influential micro parameter was particle friction coefficient. This micro parameter was calibrated with the data from triaxial tests for different combinations of soil moisture levels and confining pressures. The calibrated particle friction coefficients varied from 0.2 to 1.0. The calibrations were done through matching the shear strengths between simulations and measurements, and the relative errors ranged between 0 and 6 %. / October 2015

In 2006 resin accounted for approximately 17% of the direct manufacturing costs for oriented strand board (OSB). Because of their increased dependency on pMDI-resins, this percentage is likely greater for oriented strand lumber (OSL) and laminated strand lumber (LSL). The cost of PF- and pMDI-resins is expected to face upward pressure as the cost of their primary constituents, natural gas and crude oil, continue to reach new highs. Therefore, there is strong economic incentive to optimize the use of resin in the production of these three products. This can be accomplished by addressing two key issues: reducing resin wastage and optimizing resin distribution on the strands. Both issues will be overcome by focusing on the blending process, where resin is applied to the strands. This work focused on development and use of a discrete element model (DEM) for simulating strand flow in a rotary drum blender using the EDEM software package. EDEM required the input of three material and three interaction properties. Development of the model involved creating the simulated environment (i.e. physical dimensions) and assigning appropriate material and interaction properties given this environment and the assumptions that were made. This was accomplished in two steps, completing baseline bench-top experiments and a literature review to determine appropriate parameters and initial value ranges for these properties, and then fine-tuning these values based on a validation process. Using the validated model, an exploratory study was conducted to determine the effect of four blender design and operating parameters (flight height, number of flights, blender rotational speed, and blender fill level) on bulk strand flow. The results were analyzed with regards to overall trends and by focusing on two perspectives, end users and blender manufacturers. It was found that there was a strong relationship between these key parameters and bulk strand flow. These results suggest that operating parameters of a blender, namely rotational speed and tilt angle, should be linked directly to the blender feed rate to ensure an optimal blending environment is maintained. In addition, manufacturers of blenders must take into consideration the range in final operating conditions when designing and positioning flights.

Tobulėjant skaitiniams metodams ir kompiuterinei technikai atsivėrė galimybė naujų, sudėtingesnių mechaninių objektų modeliavimui. Turėdami naujus sudėtingesnių objektų modelius tyrėjai gali pritaikyti aprašytas ir sumodeliuotas šių objektų savybes su mikro struktūros ypatumais esamų ar busimų savybių nustatymui bei naujų medžiagų kūrimui. Tam intensyviai naudojami kaip eksperimentiniai taip ir skaitiniai metodai, kurių tobulinimui šiuo metu yra skiriamas labai didelis dėmesys. Skaitinis eksperimentas, kaip medžiagos tyrimo būdas pasitelkiamas dar ir todėl kad yra pigesnis ir leidžia interpretuoti jau žinomus eksperimentų rezultatus, o taip suteikia žinių naujiems tyrimams. Vienas iš metodų, kuris modeliuoja makroskopines medžiagų savybes remdamasis medžiagos mikro savybėmis yra diskrečiųjų elementų metodas (DEM). DEM metodas remiasi idėja, kad bet kokia fizikinė struktūra gali būti aprašyta kaip judančių dalelių sistema. Ši idėja pradėta taikyti ir vientisam deformuojamam kūnui aprašyti. Skirtingai nuo biriųjų medžiagų, vientiso kūno dalelės ir tarp jų egzistuojančios sąveikos yra kitokios prigimties, o jų modeliai yra fizikinės ir matematinės abstrakcijos rezultatas. Vientiso deformuojamo kūno modeliavimas diskrečiais elementais yra tik pradinėje stadijoje, o vientiso požiūrio į diskrečių elementų modelius dar nėra. Yra kelios hipotetinės versijos, grindžiamos skirtingais požiūriais. Taikant DEM kūnui, pirmas žingsnis būtu tampriųjų savybių modeliavimas. Tai yra... [toliau žr. visą tekstą] / Development of numerical methods and computation environments opened the possibility of new, more sophisticated mechanical objects modelling. In this context it is natural desire of the researchers to describe macroscopic mechanical characteristics of the materials by their microstructure, which can be adapted for simulation of the existing and future materials. For this purpose researchers are using intensively experimental and numerical methods for the development of which the highest priority is given. Numerical experiments are used because they are cheaper and allow the interpretation of already known results of experiments and provide information to new investigations. One of the methods used for modelling of macroscopic properties modelling is based on microscopic properties of material is discrete element method (DEM). The DEM traditionally was applied for the granular materials. The basic idea of DEM is that any physical structure could be described as a system of moving particles. This idea could be also applied to the description of solid deformable body. Particles forming solid body and existing interaction between them are of different nature than the granular materials because their models are often the result of physical and mathematical abstraction. The modelling of solid deformable body with the discrete elements is just at the initial stage and the unified approach to discrete elements models doesn’t exist. There are several versions of models, based... [to full text]

Development of numerical methods and computation environments opened the possibility of new, more sophisticated mechanical objects modelling. In this context it is natural desire of the researchers to describe macroscopic mechanical characteristics of the materials by their microstructure, which can be adapted for simulation of the existing and future materials. For this purpose researchers are using intensively experimental and numerical methods for the development of which the highest priority is given. Numerical experiments are used because they are cheaper and allow the interpretation of already known results of experiments and provide information to new investigations. One of the methods used for modelling of macroscopic properties modelling is based on microscopic properties of material is discrete element method (DEM). The DEM traditionally was applied for the granular materials. The basic idea of DEM is that any physical structure could be described as a system of moving particles. This idea could be also applied to the description of solid deformable body. Particles forming solid body and existing interaction between them are of different nature than the granular materials because their models are often the result of physical and mathematical abstraction. The modelling of solid deformable body with the discrete elements is just at the initial stage and the unified approach to discrete elements models doesn’t exist. There are several versions of models, based on... [to full text] / Tobulėjant skaitiniams metodams ir kompiuterinei technikai atsivėrė galimybė naujų, sudėtingesnių mechaninių objektų modeliavimui. Turėdami naujus sudėtingesnių objektų modelius tyrėjai gali pritaikyti aprašytas ir sumodeliuotas šių objektų savybes su mikro struktūros ypatumais esamų ar busimų savybių nustatymui bei naujų medžiagų kūrimui. Tam intensyviai naudojami kaip eksperimentiniai taip ir skaitiniai metodai, kurių tobulinimui šiuo metu yra skiriamas labai didelis dėmesys. Skaitinis eksperimentas, kaip medžiagos tyrimo būdas pasitelkiamas dar ir todėl kad yra pigesnis ir leidžia interpretuoti jau žinomus eksperimentų rezultatus, o taip suteikia žinių naujiems tyrimams. Vienas iš metodų, kuris modeliuoja makroskopines medžiagų savybes remdamasis medžiagos mikro savybėmis yra diskrečiųjų elementų metodas (DEM). DEM metodas remiasi idėja, kad bet kokia fizikinė struktūra gali būti aprašyta kaip judančių dalelių sistema. Ši idėja pradėta taikyti ir vientisam deformuojamam kūnui aprašyti. Skirtingai nuo biriųjų medžiagų, vientiso kūno dalelės ir tarp jų egzistuojančios sąveikos yra kitokios prigimties, o jų modeliai yra fizikinės ir matematinės abstrakcijos rezultatas. Vientiso deformuojamo kūno modeliavimas diskrečiais elementais yra tik pradinėje stadijoje, o vientiso požiūrio į diskrečių elementų modelius dar nėra. Yra kelios hipotetinės versijos, grindžiamos skirtingais požiūriais. Taikant DEM kūnui, pirmas žingsnis būtu tampriųjų savybių modeliavimas. Tai yra... [toliau žr. visą tekstą]