For members and flat slabs without shear reinforcement, the shear and punching shear strength are often the determining design criteria. These failure modes are characterized by a fragile behaviour implying possible partial or total collapse of the structure. Despite extensive research in this field, shear and punching shear in reinforced and prestressed concrete structures, remain complex phenomena so much that the current approach is often empirical or simplified. The ability of Steel Fibre Reinforced Concrete (SFRC) to reduce shear reinforcement in reinforced and prestressed concrete members and slabs,or even eliminate it, is supported by several experimental studies. However its practical application remains marginal mainly due to the lack of standard, procedures and rules adapted to its performance. The stationary processes in precast industry offer optimal possibilities for using high performance cementitious materials such as Self Compacting Concrete (SCC) and High Strength Concrete (HSC). For the author, the combination of High Performance Concrete and steel fibres is the following step in the development and the optimization of this industry. The High Performance Fibre Reinforced Concrete (HPFRC) stands between conventional SFRC and Ultra-High Performance Fibre Reinforced Concrete (UHPFRC). The HPFRC exhibiting a good strength/cost ratio is, thus, an alternative of UHPFRC for precast elements. The principal aim of this work was to analyse the shear and punching shear behaviour of HPFRC and UHPFRC structures without transversal reinforcement and to propose recommendations and design models adapted for practitioners. Several experimental studies on structural elements, i.e. beams and slabs, were undertaken for this purpose. Firstly, an original experimental campaign was performed on pre-tensioned members in HPFRC. A total number of six shear-critical beams of a 3.6 m span each, and two full scale beams of a 12 m span each, were tested in order to evaluate the shear and flexural strength. The principal parameter between the specimens was the fibres (...)

A capacidade de carga de estacas pode ser determinada experimentalmente através de provas de cargas estáticas ou de ensaios de carregamentos dinâmicos, conforme as prescrições da NBR 6122:2010. Na sua forma tradicional, o ensaio de carregamento dinâmico, fundamentado na teoria da equação da onda unidimensional, consiste em aplicar uma sequência de golpes de energia aproximadamente constante no conjunto de amortecedores colocado sobre a estaca e medir, no seu topo, valores de deformação específica e aceleração em função do tempo. Esse ensaio evoluiu ao longo dos anos com o avanço da tecnologia e com o desenvolvimento de modelos numéricos, que permitem simular a prova de carga estática na estaca ensaiada dinamicamente. Outra evolução, uma verdadeira \"revolução\", foi a introdução do método de energia crescente proposto por Aoki (1989). O presente estudo é uma iniciativa de aprofundamento do método de energia crescente com foco na definição da envoltória máxima de resistência lateral, permitindo recuperar as mobilizações dos atritos no fuste da estaca, perdidas em golpes anteriores ao de máxima energia aplicada, principalmente em camadas próximas ao topo da estaca. Este procedimento foi denominado Método da Envoltória Máxima de Resistência Lateral. É apresentada uma revisão bibliográfica envolvendo provas de cargas estáticas e ensaios de carregamentos dinâmicos para determinar a capacidade de carga em estacas, junto com os métodos analíticos, empíricos e semiempíricos, disponíveis na literatura técnica. São apresentados três estudos de casos de obras no Estado de São Paulo, nos quais foram realizados ensaios estáticos e dinâmicos nas mesmas estacas, sendo 2 pré-moldadas e uma escavada. A aplicação do Método da Envoltória Máxima de Resistência Lateral conduziu a uma definição de maiores capacidades de carga através do CAPWAP, com curvas carga-recalque simuladas aderentes às das provas de cargas estáticas. Além disso, permitiu estimativas mais precisas do efeito de \"setup\" a longo prazo e forneceu maiores detalhes a respeito do comportamento do sistema estaca-solo. / The load capacity of piles can be experimentally determined through static load tests or high strain dynamic load tests, as stated with the requirements of NBR 6122:2010. In its traditional form, the dynamic load test, based on the theory of the one-dimensional wave equation, consists of applying a sequence of constant energy blows upon the pile, and by these blows are measured values of deformation and acceleration as a function of time. The traditional method has evolved through technological advances along the years, with the development of numerical models that simulate the static load test of a pile dynamically tested. Another evolution, a true called \"revolution\", was the introduction of a method of increasing energy test created and proposed by Aoki (1989). The traditional method has evolved through technological advances along the years. The present study is an initiative to deepen the increasing energy method focusing on the definition of the maximum lateral resistance envelope, allowing recovering the mobilized resistance along the shaft, lost in blows prior to the maximum applied energy, especially in layers close to the top of the pile. This procedure was called the Maximum Envelope of Shear Strength. A review is presented involving static load tests and dynamic load tests to determine the load capacity on piles, together with the analytical, empirical and semi empirical methods available in the literature. Three case studies from the State of São Paulo are presented, where static and dynamic tests were performed on the same piles, two driven and one cast-in-place piles. The application of the Maximum Envelope of Shear Strength led to a definition of higher load capacities through the CAPWAP, with simulated load-displacement curves with good correlations in comparison with the static load tests. In addition, it allowed for more accurate estimates of the long-term \"set-up\" effect and provided more detail about the behavior of the pile-soil system.

A capacidade de carga de estacas pode ser determinada experimentalmente através de provas de cargas estáticas ou de ensaios de carregamentos dinâmicos, conforme as prescrições da NBR 6122:2010. Na sua forma tradicional, o ensaio de carregamento dinâmico, fundamentado na teoria da equação da onda unidimensional, consiste em aplicar uma sequência de golpes de energia aproximadamente constante no conjunto de amortecedores colocado sobre a estaca e medir, no seu topo, valores de deformação específica e aceleração em função do tempo. Esse ensaio evoluiu ao longo dos anos com o avanço da tecnologia e com o desenvolvimento de modelos numéricos, que permitem simular a prova de carga estática na estaca ensaiada dinamicamente. Outra evolução, uma verdadeira \"revolução\", foi a introdução do método de energia crescente proposto por Aoki (1989). O presente estudo é uma iniciativa de aprofundamento do método de energia crescente com foco na definição da envoltória máxima de resistência lateral, permitindo recuperar as mobilizações dos atritos no fuste da estaca, perdidas em golpes anteriores ao de máxima energia aplicada, principalmente em camadas próximas ao topo da estaca. Este procedimento foi denominado Método da Envoltória Máxima de Resistência Lateral. É apresentada uma revisão bibliográfica envolvendo provas de cargas estáticas e ensaios de carregamentos dinâmicos para determinar a capacidade de carga em estacas, junto com os métodos analíticos, empíricos e semiempíricos, disponíveis na literatura técnica. São apresentados três estudos de casos de obras no Estado de São Paulo, nos quais foram realizados ensaios estáticos e dinâmicos nas mesmas estacas, sendo 2 pré-moldadas e uma escavada. A aplicação do Método da Envoltória Máxima de Resistência Lateral conduziu a uma definição de maiores capacidades de carga através do CAPWAP, com curvas carga-recalque simuladas aderentes às das provas de cargas estáticas. Além disso, permitiu estimativas mais precisas do efeito de \"setup\" a longo prazo e forneceu maiores detalhes a respeito do comportamento do sistema estaca-solo. / The load capacity of piles can be experimentally determined through static load tests or high strain dynamic load tests, as stated with the requirements of NBR 6122:2010. In its traditional form, the dynamic load test, based on the theory of the one-dimensional wave equation, consists of applying a sequence of constant energy blows upon the pile, and by these blows are measured values of deformation and acceleration as a function of time. The traditional method has evolved through technological advances along the years, with the development of numerical models that simulate the static load test of a pile dynamically tested. Another evolution, a true called \"revolution\", was the introduction of a method of increasing energy test created and proposed by Aoki (1989). The traditional method has evolved through technological advances along the years. The present study is an initiative to deepen the increasing energy method focusing on the definition of the maximum lateral resistance envelope, allowing recovering the mobilized resistance along the shaft, lost in blows prior to the maximum applied energy, especially in layers close to the top of the pile. This procedure was called the Maximum Envelope of Shear Strength. A review is presented involving static load tests and dynamic load tests to determine the load capacity on piles, together with the analytical, empirical and semi empirical methods available in the literature. Three case studies from the State of São Paulo are presented, where static and dynamic tests were performed on the same piles, two driven and one cast-in-place piles. The application of the Maximum Envelope of Shear Strength led to a definition of higher load capacities through the CAPWAP, with simulated load-displacement curves with good correlations in comparison with the static load tests. In addition, it allowed for more accurate estimates of the long-term \"set-up\" effect and provided more detail about the behavior of the pile-soil system.

[pt] A resistência ao cisalhamento de descontinuidades é fortemente influenciada pela rugosidade e pela tensão normal aplicada, além de outras propriedades das descontinuidades. A sua avaliação é de vital importância nos projetos de escavações subterrâneas, estabilidade de taludes, túneis, fundações e outros tipos de obras da engenharia em rochas. O propósito principal deste trabalho foi o desenvolvimento de um equipamento de cisalhamento direto convencional que permite avaliar a resistência ao cisalhamento em descontinuidades de rochas sem preenchimento, em escala de laboratório. A força normal e a força cisalhante foram aplicadas através de atuadores hidráulicos servo controlados. Encontram-se acoplados nos atuadores os dispositivos para medir cargas e deslocamentos verticais e horizontais. O controlador de aquisição de dados converte os sinais mecânicos e elétricos em dados digitais. Os dados foram registrados nos intervalos desejados num computador. Foram feitos ensaios de cisalhamento em juntas artificiais e naturais de dois tipos de gnaisse, o Microclina Gnaisse e o Plagioclásio biotita hornblenda gnaisse. Os resultados obtidos apresentaram uma variação no padrão da rugosidade, com uma diminuição da dispersão com o aumento da escala das amostras, as juntas naturais apresentaram uma dispersão maior nos resultados do que as juntas artificiais. Os parâmetros de resistência obtidos experimentalmente foram então comparados, com os parâmetros de resistência obtidos através do método empírico de Barton e Choubey (1977) e também com dados encontrados na bibliografia. Os resultados mostram-se satisfatórios, validando o equipamento desenvolvido. / [en] The shear strength of discontinuities is strongly influenced by the roughness and the normal stress applied, as well as other properties of the discontinuities. Their assessment is of vital importance in underground excavation projects, slope stability, tunnels, foundations and other types of rock engineering activities. The main purpose of this work was the development of a conventional direct shear equipment to determine the shear strength of unfilled rock discontinuities at laboratory scale. Normal force and shear force were applied with servo controlled hydraulic actuators. The devices for measuring loads and vertical and horizontal displacements are coupled to the actuators. The data acquisition controller converts the mechanical and electrical signals into digital data. The data was recorded at the desired intervals on a computer. Shear tests were performed on artificial and natural joints of two types of gneiss, the Microcline gneiss and the Plagioclase biotite hornblende gneiss, common rocks in the southern region of Rio de Janeiro city. The results showed a variation in the roughness pattern, with a decrease of the dispersion with the increase of the samples size, the natural joints presented a greater dispersion in results than the artificial joints. The resistance parameters obtained experimentally were then compared with the resistance parameters obtained through the empirical method of Barton and Choubey (1977) and also with data found in the literature. The results obtained are satisfactory, validating the developed equipment.

Pour les poutres et les dalles ne comportant pas d'armatures de cisaillement, la résistance à l'effort tranchant ou au poinçonnement est souvent un critère important de dimensionnement. Ce type de rupture est caractérisé par un comportement fragile pouvant conduire à l'effondrement partiel voir total de la structure. Malgré de nombreuse recherche dans ce domaine, la résistance à l'effort tranchant et au poinçonnement des structure en béton armé ou précontraint demeure un phénomène complexe et dont l'approche normative est souvent empirique est simplifiée. La capacité des bétons renforcés de fibres métalliques à réduire voir à remplacer totalement les armatures de cisaillement des structures en béton armé et précontraint a été mis en évidence par plusieurs études expérimentales. Cependant, et malgré ses nombreux atouts, l'application à l'échelle industrielle des bétons de fibres est restée marginal, principalement due au manques d'un cadre normatif cohérent et reconnu. Les processus fixes d'une usine de préfabrication d'éléments en béton offre des possibilités optimales pour utiliser des matériaux cimentaires à hautes performances tel que les bétons autoplaçant, les bétons à hautes résistances, etc. Du point de vue de l'auteur, l'utilisation de bétons à hautes performances renforcés de fibres métalliques est le pas de développement et d'optimisation pour cette industrie. Les Bétons Fibrés à Hautes Performances (BFHP) reprennent une matrice similaire aux Bétons à Hautes Performances (BHP) auxquels est ajouté une certaine quantité de fibres métalliques conférant au matériau un comportement au niveau de la structure exploitable dans le dimensionnement. Les BFHP présentent un ratio résistances/coûts intéressant ainsi qu'une alternative au Béton Fibré Ultra-Performants (BFUP). L'objectif principal de ce travail est d'analyser le comportement au cisaillement et au poinçonnement d'éléments de structures en BFHP et en BFUP sans armatures de cisaillement et proposé des recommandations et des règles de dimensionnement adaptées aux ingénieurs de la pratique (…) / For members and flat slabs without shear reinforcement, the shear and punching shear strength are often the determining design criteria. These failure modes are characterized by a fragile behaviour implying possible partial or total collapse of the structure. Despite extensive research in this field, shear and punching shear in reinforced and prestressed concrete structures, remain complex phenomena so much that the current approach is often empirical or simplified. The ability of Steel Fibre Reinforced Concrete (SFRC) to reduce shear reinforcement in reinforced and prestressed concrete members and slabs,or even eliminate it, is supported by several experimental studies. However its practical application remains marginal mainly due to the lack of standard, procedures and rules adapted to its performance. The stationary processes in precast industry offer optimal possibilities for using high performance cementitious materials such as Self Compacting Concrete (SCC) and High Strength Concrete (HSC). For the author, the combination of High Performance Concrete and steel fibres is the following step in the development and the optimization of this industry. The High Performance Fibre Reinforced Concrete (HPFRC) stands between conventional SFRC and Ultra-High Performance Fibre Reinforced Concrete (UHPFRC). The HPFRC exhibiting a good strength/cost ratio is, thus, an alternative of UHPFRC for precast elements. The principal aim of this work was to analyse the shear and punching shear behaviour of HPFRC and UHPFRC structures without transversal reinforcement and to propose recommendations and design models adapted for practitioners. Several experimental studies on structural elements, i.e. beams and slabs, were undertaken for this purpose. Firstly, an original experimental campaign was performed on pre-tensioned members in HPFRC. A total number of six shear-critical beams of a 3.6 m span each, and two full scale beams of a 12 m span each, were tested in order to evaluate the shear and flexural strength. The principal parameter between the specimens was the fibres (…)

In Sweden, the rock mass is commonly used for construction of tunnels and caverns. The rockmass is also used as a foundation for large structures such as bridge abutments and dams. Forthese structures, the understanding of the rock mechanical properties play a key role for reachingan acceptable safety level and minimizing cost. One of the properties that has a high uncertaintyis the shear strength of rock joints. These rock joints constitute the weakest link in the rock massand often govern it´s strength. The uncertainty lies in the amount of factors that affect the shearstrength such as the degree of weathering, the matedness, the roughness of the surface and thescale. Various authors have tried to develop a failure criterion that can predict the peak shearstrength of rock joints and takes into account the influence of the various factors.The aim of this thesis is to evaluate the ability of the newly developed Casagrande et al.criterion to determine the peak shear strength for perfectly mated and natural rock joints withdifferent degrees of matedness. All samples analyzed in this thesis have been scanned andcustomized to run in the programmed version of the Casagrande et al. criterion. This iterativeprocess will stop as the application reach the apparent dip angle where the total shearing force issmaller than the total sliding force. This angle combined with the basic friction angle gives thepeak friction angle for calculations of the peak shear strength.The result show that the Casagrande et al. criterion can predict the peak shear strength forperfectly mated joint. However, for the natural rock joint, as the degree of matedness decreases,the accuracy of the prediction of the peak shear strength decreases. The conclusion of this studyis that the Casagrande’s criterion cannot determine the peak shear strength of natural rock jointsand that further development of the Casagrande et al. criterion is needed taking this parameterinto account. / Sverige är berg ett vanligt material för byggande av tunnlar och bergrum. För dessakonstruktioner spelar bergegenskaperna en nyckelroll för att nå en acceptabel säkerhetsnivåoch minimera kostnaden. En av de egenskaper som har stor osäkerhet är skjuvhållfastheten förbergsprickor. Osäkerheten ligger i de många faktorer som påverkar skjuvhållfastheten, såsomgraden av vittring, passning, ytans råhet och skala. Olika författare har försökt att anpassa ettbrottkriterium för bergsprickor som tar hänsyn till faktorernas inflytande och som kan användastill att uppskatta den maximala skjuvhållfastheten.Syftet med detta examensarbete är att utvärdera förmågan hos det nyligen utveckladebrottkriteriet av Casagrande et al. att bestämma den maximala skjuvhållfastheten för perfektpassade sprickor och naturliga sprickor med olika grad av passning. Alla prover i detta arbetehar skannats in och anpassats för att köras i den programmerade algoritmen som beräknar denmaximala skjuvhållfastheten enligt kriteriet av Casagrande et al.. Kriteriet använder sig av eniterativ process som pågår tills algoritmen når den vinkel där den totala skjuvkraften är mindreän den totala glidkraften. Denna vinkel kombinerad med sprickans basfriktionsvinkeln ger denmaximala friktionsvinkeln för beräkning av skjuvhållfastheten.Resultaten visar att Casagrande et al. kan förutspå den maximala skjuvhållfastheten förperfekt passade sprickor. När passningsgraden minskar för naturliga bergsprickor minskar kriterietsförmåga att prediktera den maximala skjuvhållfastheten. Slutsatsen från detta arbete äratt kriteriet av Casagrande et al. kan prediktera skjuvhållfastheten för perfekt passade sprickormen saknar förmågan att beakta inverkan från passning, vilket leder till att skjuvhållfasthetenöverskattas om kriteriet användas på naturliga sprickor som inte är perfekt passade. Fortsattforskning krävs för att vidareutveckla kriteriet så att graden av passning kan beaktas.

Master of Science / Department of Mechanical and Nuclear Engineering / Kevin Lease / Carbon fiber reinforced composites (CFRP’s) are a mainstay in many industries, including the aerospace industry. When composite components are damaged on an aircraft, they are typically repaired with a composite patch that is placed over the damaged material and cured into the existing composite material. This curing process involves knowledge of the curing time necessary to sufficiently cure the patch. The inexact nature of curing composites on aircraft causes a significant waste of time and material when patches are unnecessarily redone. Knowing how differences in cure cycle affect the strength of the final material could reduce this waste. That is the focus of this research. In this research, the interfacial shear strength (IFSS) of carbon fiber/epoxy composites was investigated to determine how changes in cure cycle affect the overall material strength. IFSS is a measure of the strength of the bond between the two materials. To measure this, the microbond method was used. In this method, a drop of epoxy is applied to a single carbon fiber. The specimen is cured and the droplet is sheared from the fiber. The force required to debond the droplet is recorded and the data is analyzed. The IFSS of AS4/Epon828, T650/Epon828, and T650/Cycom 5320-1 composites were evaluated. For the former two material systems, a cure cycle with two steps was chosen based on research from others and then was systematically varied. The final cure time was changed to determine how that parameter affected the IFSS. It was found that as the final cure time increased, so did the IFSS and level of cure achieved by the composite to a point. Once the composite reached its fully cured state, increasing the final cure time did not noticeably increase the IFSS. For the latter material system (T650/Cycom 5320-1), the two cure cycles recommended by the manufacturer were tested. These had different initial cure steps and identical final cure steps. Although both cure cycles caused high IFSS, the cycle with the higher initial temperature, but shorter initial cure time achieved a higher level of cure than that with a longer time, but shorter temperature.

Geotechnicans in Sweden and rest of Scandinavia have a wide experience of stability calculations in cohesive soils. The two main parameters for this type of calculations are the undrained shear strength and the preconsolidation pressure. The most common methods in Sweden to determine the undrained shear strength in field is the vane shear strength test and CPT-test, in laboratories the fall cone test is well used. To determine the preconsolidation pressure CRS-analyses are well used. For more accurate measurements the odeometer tests are more suitable. However this method is both expensive and time-consuming form of analysis from a commercial aspect. Therefore is different correlation equations used as a compliment in these different stability evaluations.  This research will focus on the empirical Hansbo Correlation and its relation to results from commercial surveys. The commercial data come from Atkins Sverige’s project data base. The results after comparing Hansbo correlation with the commercial data showed on a significant divergence, which indicate a great unsureness of the Hansbo correlation. As a result of this contingency it is of importance to take cautiousness in the use of empirical correlations in stability calculations.

Thesis (PhD (Civil Engineering))--Stellenbosch University, 2008. / The cold bituminous mixtures, which are the subject of this study, are obtained by mixing mineral aggregate with either bitumen emulsion or foamed bitumen at ambient temperatures. These techniques are frequently used in Cold In-Place Recycling whereby typically the top 150 – 250 mm of the existing pavement is reworked, as a rehabilitation measure when structural maintenance is required. To differentiate from the cold mixes for surfacing layers the term Bitumen Stabilised Materials (BSM’s) is adopted here. The increased use of BSM’s, shortcomings in the existing design guidelines and manuals and ongoing developments in the concepts and understanding of these materials require further research into the fundamental properties and behaviour of BSM’s. Achieving a better understanding of the fundamental performance properties of BSM’s is the main objective of this study, with a view to using the extended knowledge for improvements to current mix design and structural design practices. The state-of-the-art of bitumen emulsion and foamed bitumen techniques is reviewed in a literature study. Current best practices in the design of BSM’s and pavements incorporating such materials is also included in this literature study. Shortcomings and areas for further improvement of the design practice have been identified. With new environmental legislation that recently came into effect in South Africa, the importance of BSM technology as an environmentally-friendlier and more sustainable construction technique is set to increase in the coming years. A laboratory testing programme was set-up to study the properties and behaviour of BSM’s and to establish links with the compositional factors, i.e. the type of binder used, the percentage of Reclaimed Asphalt Pavement (RAP) in the mix and the addition of a small dosage of cement as active filler. The mineral aggregates used were sourced in the USA and consisted of crushed limestone rock and RAP millings. These were blended in two different proportions of crushed rock : RAP, i.e. 3:1 (with 3.6 % residual binder) and 1:3 (with 2.4 % residual binder). Tri-axial testing (150 mm diamter) was carried out to determine shear parameters, resilient modulus and permanent deformation behaviour, while four-point beam testing was carried out to determine strain-at-break, flexural stiffness and fatigue behaviour. It was found that the process of bitumen stabilisation improves the shear strength of the material, particularly in case 1 % of cement is added as active filler. This increase in shear strength is entirely the result of increased cohesion. There is a good correlation between the shear strength and the resilient modulus of BSM’s. The resilient modulus of BSM is stress-dependent and the Mr-θ model is adequate to model the resilient modulus of the blends with a low percentage of RAP. For the blends with a higher percentage of RAP this model cannot be applied and the resilient modulus reduces in stiffness at higher deviator stress ratios. A considerable part of the efforts of this study were dedicated to characterise and model the permanent deformation behaviour. The General Permanent Deformation Law as originally developed by Francken applies also to BSM’s. An improved nonlinear method to converge at a solution for the model parameters that describe the tertiary flow part of this deformation law was developed as part of this study. Parameters that can be derived from the first stage of the permanent deformation test, i.e. initial strain and initial strain rate as defined in this study, were found that correlate well with the model parameters that describe the first linear part of the deformation law. Critical deviator stress ratios for the several mixes tested were determined. When BSM’s are subjected to loading below these ratios, tertiary flow is unlikely to occur. A high variability was generally found in the four-point beam test results, especially for the strain-at-break. Specimen preparation protocols and the quality of the beam specimens are of utmost importance when performing four-point beam tests on BSM’s. This limits the practical applications of the strain-at-break test. Trends observed in the strain-at-break were also inconsistent and sometimes not in line with the other type of tests. BSM’s exhibit a visco-elastic behaviour, which was determined by flexural stiffness testing, however, to a lesser extent than HMA. Phase angles and Black Diagrams were developed for the BSM’s tested, which also made it possible to determine the parameters of the Burgers Model, which is a mechanical model describing viscoelastic behaviour. Fatigue relationships were also developed for the BSM’s tested. The fatigue performance of these mixes is lower than for selected HMA mixes. The foamed BSM generally showed better fatigue life than emulsion BSM, however, the lower initial stiffness of the foamed BSM’s may contribute to a perceived longer fatigue life. For the mixes tested, the flexural stiffness of foamed BSM’s is generally also lower than that of emulsion BSM’s It is recommended that the mix design of BSM’s be split into two phases. During the first phase the usually large number of variables could be reduced to a selected few by means of UCS and ITS indicator testing. Subsequently, more fundamental parameters should be determined during the second phase, such as shear strength and resilient modulus, as well as permanent deformation behaviour. The fact that commercial laboratories in South Africa do not have tri-axial testing facilities is currently a practical limiting factor. Initiatives currently underway to develop “simple” shear tests are welcomed in this regard. It is proposed that classification of BSM is based on shear strength. There are indications that shear failure in BSM is more critical than failure as a result of fatigue. The effect of curing resulting in an increase in BSM stiffness in the period after construction, i.e. typically 6 to 18 months, is currently ignored in structural design models. The rapid stiffness reduction of BSM’s during the first period after construction in the current structural design models and also found during Accelerated Pavement Testing is not being observed in Long-Term Pavement Performance (LTPP). On the contrary, an increase in stiffness is observed in LTPP. This would indicate that stiffness reduction as a result of fatigue does not occur or is overshadowed by the effect of curing and that fatigue as a failure mechanism of BSM’s is currently over-emphasized.

In simulation of closely- or separately-joined rock masses, stability of rock blocks is of primary concern. However, there seems to be no approach that can handle general modes of simultaneous sliding and truly large rotation under general forces, including non-conservative forces such as water forces. General causes of failure for rock blocks, such as limit points, bifurcation points, and dynamic instability (divergence and flutter), have never been addressed. This research implements a formulation, called BS3D(an incremental-iterative algorithm introduced by Tonon), for analyzing general failure modes of rock blocks under conservative and non-conservative forces. Among the constitutive models for rock fractures developed over the years, Barton's empirical model has been widely used because it is easy to apply and includes several important factors associated with fracture characteristics. Although Barton's failure criterion predicts peak shear strength of rock fractures with acceptable precision, it has some weaknesses in estimating the peak shear displacement, post-peak shear strength, dilation, and surface degradation in unloading and reloading. In this dissertation, modifications are made to Barton's original model in order to address these weaknesses. The modified Barton’s model is validated by a series of direct shear tests on rock fractures and implemented in BS3D to consider the dilatant behavior of fractures. The mechanical behavior of a rock block formed in the roof of a tunnel is governed by its geometry, the mechanical characteristics and the deformability of the fractures forming the block, the deformability of the block and that of the surrounding rock mass, and the stresses within the rock. BS3D, after verification and validation, is used to investigate the effect of dilatancy on stability of rock blocks formed in the roof of a circular tunnel. High-velocity plunging jets, issuing from hydraulic artificial or natural structures, can result in scouring of the rock riverbed or the dam toe foundation. Assessment of the extent of scour is necessary to ensure the safety of the dam and to guarantee the stability of its abutments. BS3D is used to investigate effect of high-velocity jet impact on stability of rock blocks in plunge pools. / text