Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on June 30, 2008). Includes bibliographical references (p. 51-57).

Most rock masses encountered in civil and mining engineering projects contain pre-existing discontinuities. These discontinuities weaken the rock masses to an extent, which depends very much on the size of engineering structure relation to discontinuity spacing. The strength and deformability of rock mass is controlled not only by the intact portion of rock, but by the characteristic of the joints that break up the mass, particularly their pattern and their orientation with respect to the in-situ stresses. In considering the effect of joints, the discrete approach emerged as an efficient tool and advocated since 1970s (Cundall, 1971). However, the numerical approach with modelling the joints explicitly has the limitation of computational complexity for modelling large-scale problems with extremely large number of joints. As an alternative to this limitation, the equivalent continuum approach models the jointed rock masses as a continuum with the equivalent properties that represent implicitly the effects of the joints. Several numerical methods have been developed by various researchers to model jointed rock masses as equivalent continuum, using various techniques. However, the existing equivalent continuum models are complicated and need more input data from experimental or field testing in order to carry out the analysis. Present approach attempts to use statistical relations, which are simple and obtained after analyzing a large data from the literature on laboratory test results of jointed rock masses. Systematic investigations were done including laboratory experiments to develop the methodologies to determine the equivalent material properties of rock mass and their stress-strain behaviour, using a hyperbolic approach (Duncan and Chang, 1970). Present study covers the development of equivalent continuum model for rock mass right from developing statistical correlations to find out equivalent material properties based on experimental results, to the implementation of the model in FLAC3D for 3-dimensional applications and subsequently verification leading to real field application involving jointed rocks. Experimental work carried out to study the strength and deformation characteristics of jointed rock by using standard laboratory tests on cylindrical specimens of plaster of Paris by introducing artificial joints. The objective was to derive the compressive strength and elastic modulus of rock mass as a function of intact rock strength/modulus and joint factor. The obtained experimental results and developed relations were compared with the previous experimental data on jointed rocks. Further, a failure criterion as proposed by Ramamurthy (1993) has been validated from these experimental results of intact and jointed rock specimens. Empirical relationships similar to Ramamurthy’s relations are established for the prediction of rock mass strength and were compared with proposed equation by Ramamurthy (1993) and are found comparable. However, the equations by Ramamurthy were based on different variety of rocks and therefore recommended for further use and were used in numerical models. For efficient application to the field problems the equivalent continuum model is implemented in the program Fast Lagrangian analysis of continua (FLAC3D). The model was rigorously validated by simulating jointed rock specimens. Element tests were conducted for both uniaxial and triaxial cases and then compared with the respective experimental results. The numerical test program includes laboratory tested cylindrical rock specimens of different rock types, from plaster of Paris representing soft rock to granite representing very hard rock. The results of the equivalent continuum modelling were also compared with explicit modelling results where joints were incorporated in the model as interfaces. To represent highly discontinuous system, the laboratory investigation on block jointed specimens of gypsum plaster (Brown and Trollope, 1970) was modelled numerically using equivalent continuum approach. To extend the applicability of the model to field applications, investigation were done by undertaking numerical modelling of two case studies underground caverns, one Nathpa Jhakri hydroelectric power cavern in Himachal Pradesh, India, and the other one Shiobara hydroelectric power cavern in Japan. This study verifies the efficiency of the present approach in estimating ground movement and stress distribution around the excavations in jointed rock masses. The modelling results were also compared with six other computation models as presented by Horii et al. (1999) for the Shiobara power house cavern. An attempt has also been made to numerically model the support system for the cavern and investigate the efficiency of reinforcements using FLAC3D. The model was also used for analyzing large scale slope in jointed rocks using the equivalent continuum model by undertaking numerical modelling of Anji bridge abutment slopes, in Jammu and Kashmir, India. Slope stability analysis is done using equivalent continuum approach for both, the original profiles as well as with the pier loads on cut profiles. Attempt was also made to exhibit the shear strength dependency of the strain though the hyperbolic stress- strain model. The shear strain developed in the slope increases with reducing the shear strength. The relationship between the shear strength reduction ratio ‘R’ and axial strain ‘ε’, for different values of failure ratio ‘Rf’ was studied and it was observed that, the value of ‘ε’ increases, as the value of ‘R’ increases especially it increases rapidly when the value ‘R’ approaches certain critical value, which varies with the value of ‘Rf’. This critical value of R is known as the critical shear strength reduction factor Rc and is highly sensitive to the confining stress. As the value of Rf increases, representing a transition from linear elastic nature to nonlinear nature, the value of critical shear strength reduction ratio also decreases. Relationship between the critical shear strength reduction ratio and the safety factor were examined to elucidate their physical meaning. It was observed that at critical value of the shear strength reduction ratio, a well defined failure shear zone developed from the toe to the crest of the slope. Intelligent models using ANNs were also developed to predict the elastic modulus of jointed rocks as an alternative to empirical equations and without predefining a mathematical model to correlate the properties.

When the point under consideration is not near to the source of vibration, the strains developed in the rock mass due to the passage of waves are usually of small magnitude, and within the elastic range. However, the rock mass may be subjected to a wide range of strain levels depending on the source of vibration and the wave frequency, even within the elastic limit. The present study is based on the two general conditions existing at field, long wave length propagation of waves and intermediate wavelength propagation of waves. When the wavelength of propagating wave is much longer than the joint spacing, it is referred to as long wavelength condition and is associated with propagation of low frequency waves across closely spaced joints. When wavelength of propagating wave is nearly equal to joint spacing, it is known as intermediate wavelength condition and is associated with propagation of high frequency waves. Long wave length propagation of waves has been studied by conducting laboratory experiments using Resonant Column Apparatus on developed plaster gypsum samples. The influence of joint types, joint spacing and joint orientation on wave propagation has been analyzed at three confining stresses under various strain levels. The wave velocities and damping ratios at various strain levels have been obtained and presented. Shear wave velocities are more dependent on confining stress than compression wave velocities across frictional joints whereas, compression wave velocities are more dependent on confining stress than shear wave velocities across filled joints. Wave velocities are at minimum and wave damping is at maximum across horizontal joints whereas wave velocities are at maximum and wave damping is at minimum across vertical joints. Shear wave velocity and shear wave damping are more dependent on joint orientations than compression wave velocity and compression wave damping. As Resonant Column Apparatus has some limitations in testing stiff samples, a validated numerical model has been developed using Discrete Element Method (DEM) that can provide resonant frequencies under torsional and flexural vibrations. It has been found from numerical simulations, that reduction of normal and shear stiffness of joint with increasing strain levels leads to wave velocity reduction in jointed rock mass. Intermediate wave length propagation of waves has been studied by conducting tests using Bender/ extender elements and the numerical simulations developed using 3DEC (Three Dimensional Distinct Element Code).Parametric study on energy transmission, wave velocities and wave amplitudes of shear and compression waves, has been carried out using the validated numerical model. The propagation of waves across multiple parallel joints was simulated and the phenomenon of multiple reflections of waves between joints could be observed. The transformations of obliquely incident waves on the joint have been successfully modeled by separating the transmitted transformed P and S waves. The frequency dependent behavior of jointed rocks has been studied by developing a numerical model and by applying a wide range of wave frequencies. It has been found that low frequency shear waves may involve slips of rock blocks depending on the strength of rock joint, leading to less transmission of energy; while low frequency compression waves are well transmitted across the joints. High frequency shear and compression waves experience multiple reflections and absorptions at joints.

The issue on variability of mechanical properties within wood has found to be increasingly prominent in recent years. On the other hand, it is known that uniformity of wood properties is essential in quality control in the timber manufacturing such as manufacturing of Glued Laminated (Glulam) timber. The AS/NZS 1328 P2 specified that the overall mechanical properties of Glulam timber can be estimated based on the MOE of the finger jointed laminates and the arrangement of the corresponding laminates. In relating to the above standard, optimisation in the arrangement of shooks’ location along the finger jointed laminate will enable determination of the overall MOE of laminates, as well as optimise the utilisation of feedstocks. In this study, a deterministic model was developed in relating the local shook’s modulus of elasticity (MOE) with the overall MOE of the corresponding finger jointed timber based on the principle of the Moment of Curvature. The projected overall MOE is calculated as a function of lengths and MOEs of individual shooks in the finger joint timber. The effect of shooks’ location can also be determined from the model. Numerical derivation of the model was addressed and the analyses of the relationships between the local shook MOEs, the overall MOE, and bending strength (MOR) were assessed. Experimental results showed that the model can effectively predicts the overall MOE, particularly on shook combinations with random and large standard deviations in shook MOEs. The errors of the predictive model were ranged from -8.17% to +0.81%. Results from the assessment on the relationships between the overall MOE and bending MOR indicated that wood failure in the combinations of small standard deviations shook MOEs was most likely to occur at the weakest point, however, wood failures may not necessarily occur in the shook with the lowest MOE in the asymmetrical MOE arrangements. This also applies to the finger jointed timber with combinations of shooks with large standard deviations for local MOEs. In addition, the relationship between dynamic MOE of shooks and the static bending overall MOE were assessed. A linear regression has been suggested for the adjusted shooks dynamic MOE at 36 mm thickness. The predictability of the model could further improve when the shook MOEs were sorted according to sawing pattern and the proposed model for quarter sawn is suggested. Lastly, economic analysis was performed based on the models available in literature and the developed model in this study. Models reported in the literature including the arithmetic mean model and model based on the shook’s minimum MOE. The results from economic analysis showed that the study’s model was most cost effective in predicting the cost of shooks based on the predicted overall finger jointed MOE using the model as compare to the arithmetic mean and the minimum shook MOE method. In conclusion, the proposed model has demonstrated to be unique, simple, effective and robust in predictive applications.

The issue on variability of mechanical properties within wood has found to be increasingly prominent in recent years. On the other hand, it is known that uniformity of wood properties is essential in quality control in the timber manufacturing such as manufacturing of Glued Laminated (Glulam) timber. The AS/NZS 1328 P2 specified that the overall mechanical properties of Glulam timber can be estimated based on the MOE of the finger jointed laminates and the arrangement of the corresponding laminates. In relating to the above standard, optimisation in the arrangement of shooks’ location along the finger jointed laminate will enable determination of the overall MOE of laminates, as well as optimise the utilisation of feedstocks. In this study, a deterministic model was developed in relating the local shook’s modulus of elasticity (MOE) with the overall MOE of the corresponding finger jointed timber based on the principle of the Moment of Curvature. The projected overall MOE is calculated as a function of lengths and MOEs of individual shooks in the finger joint timber. The effect of shooks’ location can also be determined from the model. Numerical derivation of the model was addressed and the analyses of the relationships between the local shook MOEs, the overall MOE, and bending strength (MOR) were assessed. Experimental results showed that the model can effectively predicts the overall MOE, particularly on shook combinations with random and large standard deviations in shook MOEs. The errors of the predictive model were ranged from -8.17% to +0.81%. Results from the assessment on the relationships between the overall MOE and bending MOR indicated that wood failure in the combinations of small standard deviations shook MOEs was most likely to occur at the weakest point, however, wood failures may not necessarily occur in the shook with the lowest MOE in the asymmetrical MOE arrangements. This also applies to the finger jointed timber with combinations of shooks with large standard deviations for local MOEs. In addition, the relationship between dynamic MOE of shooks and the static bending overall MOE were assessed. A linear regression has been suggested for the adjusted shooks dynamic MOE at 36 mm thickness. The predictability of the model could further improve when the shook MOEs were sorted according to sawing pattern and the proposed model for quarter sawn is suggested. Lastly, economic analysis was performed based on the models available in literature and the developed model in this study. Models reported in the literature including the arithmetic mean model and model based on the shook’s minimum MOE. The results from economic analysis showed that the study’s model was most cost effective in predicting the cost of shooks based on the predicted overall finger jointed MOE using the model as compare to the arithmetic mean and the minimum shook MOE method. In conclusion, the proposed model has demonstrated to be unique, simple, effective and robust in predictive applications.

A presente dissertação enfoca as características de resistência ao cisalhamento e os mecanismos básicos que governam o fenômeno de atrito em rochas fraturadas. Especial atenção é dedicada à identificação de fatores geométricos e geotécnicos importantes e a sua relação com o comportamento e esforços resistentes de rochas fraturadas. A caracterização de fraturas por meio de parâmetros geomecânicos adequados permitirá incluí-los nos modelos de cálculo e simular mais realisticamente o comportamento geomecânico do maciço rochoso fraturado. / This thesis focuses on the shear strenght and mechanisms that change the shear characteristics of jointed rocks. Special attention was devoted to the identification of geometric and geotechnical factors and its relationship with the behavior and strenght of jointed rocks. The characterization of the fractures by apropriated geomechanical parameters Will permite to include them in the models and to simulate more realistically the behavior of fractured rock mass.

A presente dissertação enfoca as características de resistência ao cisalhamento e os mecanismos básicos que governam o fenômeno de atrito em rochas fraturadas. Especial atenção é dedicada à identificação de fatores geométricos e geotécnicos importantes e a sua relação com o comportamento e esforços resistentes de rochas fraturadas. A caracterização de fraturas por meio de parâmetros geomecânicos adequados permitirá incluí-los nos modelos de cálculo e simular mais realisticamente o comportamento geomecânico do maciço rochoso fraturado. / This thesis focuses on the shear strenght and mechanisms that change the shear characteristics of jointed rocks. Special attention was devoted to the identification of geometric and geotechnical factors and its relationship with the behavior and strenght of jointed rocks. The characterization of the fractures by apropriated geomechanical parameters Will permite to include them in the models and to simulate more realistically the behavior of fractured rock mass.

Jointed goatgrass (Aegilops cylindrica Host; 2n=4x=28; CCDD) is an agriculturally important species both as a weed and as a genetic resource for wheat (Triticum aestivum L.; 2n=6x=42; AABBDD) improvement. In order to better understand the evolution of this species, the diversity of Ae. cylindrica was evaluated along with its progenitors, Ae. markgrafii (Greuter) Hammer (2n=2x=14; CC) and Ae. tauschii Coss. (2n=2x=14; DD), using chloroplast and nuclear microsatellite markers. Ae. cylindrica had lower levels of plastome and nuclear diversity than its progenitors. The plastome diversity of Ae. cylindrica was lower than its nuclear diversity. Ae. cylindrica was found to have either C-or D-type plastomes, derived from Ae. markgrafii or Ae. tauschii, respectively, where the C-type plastome was found to occur at a lower frequency than the D-type plastome. The nuclear genomes of Ae. cylindrica accessions with C-or D-type plastome were found to be very closely related, suggesting a monotypic origin. Furthermore, analyses suggests that Ae. tauschii ssp. tauschii contributed its D genome and D-type plastome to Ae. cylindrica. Ae. cylindrica accessions collected near Van Lake in southeastern Turkey, an area where Ae. tauschii ssp. tauschii and Ae. markgrafii overlap, showed high allelic diversity and may represent the site where Ae. cylindrica formed. Population structure analyses suggested a lack of regional genetic structure in Ae. cylindrica and evidence of migration of Ae. cylindrica among various regions. Finally, Ae. cylindrica accessions in the USA were found to be closely related to accessions from at least three regions of its native range central Anatolia, central East Turkey and western Armenia, and Caucasia. Wheat and jointed goatgrass are closely related and both have the D-genome. These two species can hybridize and produce backcross derivatives under natural conditions, a situation that may allow gene flow between these two species. In order to better understand mating patterns between these two species, a total of 413 first-generation backcross (BC₁) seeds obtained from 127 wheat-jointed goatgrass F₁ hybrids, produced under natural conditions, were evaluated for their parentage using chloroplast and nuclear microsatellite markers. Of the 127 F₁ hybrids evaluated, 109 had jointed goatgrass as the female parent, while the remaining 18 F₁ plants had wheat as the female parent. Of the 413 BC₁ plants analyzed, 358 had wheat and 24 had jointed goatgrass as the recurrent male parent. The male parentage of 31 BC₁ plants could not be determined. Although the majority of hybrids were pollinated by wheat, backcrossing of hybrids to jointed goatgrass would enable gene flow from wheat to jointed goatgrass. Though the observed frequency of jointed goatgrass-backcrossed hybrids (F₁ X jointed goatgrass) was low under field conditions, their absolute number is dependent on frequency of hybrids, which in turn, depends on the density of jointed goatgrass in wheat fields. Therefore, the recommendations to control jointed goatgrass in wheat fields and adjacent areas and to plant jointed goatgrass free wheat seed should be followed in order to avoid gene flow from wheat to jointed goatgrass. / Graduation date: 2006

Dowel bars in jointed plain concrete pavement (JPCP) have the important function of transferring wheel loads from one slab to the other, hence ensuring that the deflections on each side of the joint are kept almost equal. As well, the dowels should not impede the concrete pavement movements due to environmental effects (temperature and moisture). Dowel bar misalignment, attributed to deficient construction practice, is a major cause of joint distress or faulting by inhibiting the free movement of the slab at the joint. To prevent these issues, tolerance guidelines on misalignment levels are implemented by transportation agencies. Review of previous studies indicate that many researchers analysed the effects of dowel bar misalignment on pavement behaviour using a pull-out test, that is a forcebased opening of the joint. These approaches neglect that joints movements in the field are strain-governed by non-linear temperature and shrinkage actions, leading to combined axial movements and curling of the slab. In this study, the fundamental dowel bar behaviour under shrinkage and thermal loading was determined through detailed 3D finite element modelling (3D-FEM). To that end, models of dowel jointed concrete slabs were developed and subjected to realistic non-linear profiles of shrinkage and thermal strains. Studies were carried out on a single-bar model, taking into account bar-concrete friction and plastic concrete behaviour. The parameters that were investigated included different configurations and levels of bar misalignment and different friction coefficients between the steel and the concrete, simulating the use of bond-breakers. To interpret the results from the numerical analysis, criteria for concrete damage were developed and used in parallel with measures of joint load transfer efficiency; these were obtained by examining the response of the slab under a Falling Weight Deflectometer (FWD) drop at the joint. The results were verified by comparing the outputs of a model consisting of one half of a slab to published data. The analysis of the models revealead that none of the models showed signs of significant damage after the application of shrinkage and two thermal cycles. Analyses with up to ten thermal cycles did not indicate progressive accumulation of damage, suggesting that for the chosen parameters there is no the concrete around the dowel bar will not fail. Models with bars placed higher in the slab and bars with angular misalignment exhibited more damage than the non-misaligned models without reaching the damage criteria used in this study. The models did not exhibit the amount of damage reported in the studies on dowel bar misalignment having used pull-out tests. It was found that no significant difference existed between uncoated and coated dowel bars models results with regards to concrete damage at the joint. However, a high coefficient of friction between the dowel and the concrete, simulating dowel bar corrosion, proved to be the most detrimental to joint integrity. All of the models performed very well with respect to joint load transfer efficiency, suggesting that the plastic strains in the concrete around the dowel did not have a significant impact on joint performance for the realistic range of parameters investigated.

Dowel bars in jointed plain concrete pavement (JPCP) have the important function of transferring wheel loads from one slab to the other, hence ensuring that the deflections on each side of the joint are kept almost equal. As well, the dowels should not impede the concrete pavement movements due to environmental effects (temperature and moisture). Dowel bar misalignment, attributed to deficient construction practice, is a major cause of joint distress or faulting by inhibiting the free movement of the slab at the joint. To prevent these issues, tolerance guidelines on misalignment levels are implemented by transportation agencies. Review of previous studies indicate that many researchers analysed the effects of dowel bar misalignment on pavement behaviour using a pull-out test, that is a forcebased opening of the joint. These approaches neglect that joints movements in the field are strain-governed by non-linear temperature and shrinkage actions, leading to combined axial movements and curling of the slab. In this study, the fundamental dowel bar behaviour under shrinkage and thermal loading was determined through detailed 3D finite element modelling (3D-FEM). To that end, models of dowel jointed concrete slabs were developed and subjected to realistic non-linear profiles of shrinkage and thermal strains. Studies were carried out on a single-bar model, taking into account bar-concrete friction and plastic concrete behaviour. The parameters that were investigated included different configurations and levels of bar misalignment and different friction coefficients between the steel and the concrete, simulating the use of bond-breakers. To interpret the results from the numerical analysis, criteria for concrete damage were developed and used in parallel with measures of joint load transfer efficiency; these were obtained by examining the response of the slab under a Falling Weight Deflectometer (FWD) drop at the joint. The results were verified by comparing the outputs of a model consisting of one half of a slab to published data. The analysis of the models revealead that none of the models showed signs of significant damage after the application of shrinkage and two thermal cycles. Analyses with up to ten thermal cycles did not indicate progressive accumulation of damage, suggesting that for the chosen parameters there is no the concrete around the dowel bar will not fail. Models with bars placed higher in the slab and bars with angular misalignment exhibited more damage than the non-misaligned models without reaching the damage criteria used in this study. The models did not exhibit the amount of damage reported in the studies on dowel bar misalignment having used pull-out tests. It was found that no significant difference existed between uncoated and coated dowel bars models results with regards to concrete damage at the joint. However, a high coefficient of friction between the dowel and the concrete, simulating dowel bar corrosion, proved to be the most detrimental to joint integrity. All of the models performed very well with respect to joint load transfer efficiency, suggesting that the plastic strains in the concrete around the dowel did not have a significant impact on joint performance for the realistic range of parameters investigated.