Construction of heavily loaded shallow foundations adjacent to deep foundation is generally avoided in common geotechnical engineering practice to minimize additional loads on deep foundations. However, with the growing trend of urbanization leading to a demand of new construction, it is not always possible to avoid such situation where a heavily loaded shallow foundation will be right next to the infrastructure resting on deep foundations. When this situation cannot be avoided, influence of soil pressures and deformations in soil, created by shallow foundation on adjacent deep foundation, must be evaluated. The study of interaction between deep foundations has been carried out by several researchers in terms of pile-soil-pile interaction. Similarly, there are many published studies on interaction between closely spaced shallow foundations in terms of bearing capacity and settlement. However, not much published literature is available for practicing engineers to analyze and design deep and shallow foundations when they are constructed adjacent to each other. Construction of heavily loaded mat adjacent to drilled shafts would cause complex interaction between the foundations. However, lateral stress and drag forces on the shafts resulting from the heavy load on the mat foundation are the two major factors that would affect the design and performance of shafts. Since there is not much literature and guidance available to analyze and design such kind of situation, a preliminary investigation was first carried out where magnitude of the drag forces and lateral forces on drilled shafts were estimated using simple geotechnical engineering principles. The limitations of preliminary analysis led to the need of more sophisticated analysis using finite element techniques. As a part of this research, a detailed parametric study using finite element techniques has been performed to better understand stress and deformation distributions, and develop simplified methods to analyze this type of problems. A stress bulb for lateral stresses under a uniformly loaded square foundation, similar to the pressure bulb for vertical stresses which is widely used in the geotechnical engineering practice, has been proposed, which provides a significant tool for practicing engineers to understand lateral stress distribution below a uniformly loaded square area and estimate lateral stresses on nearby deep foundations. Similarly, a deformation bulb under a uniformly loaded square foundation is proposed. A new term “Isodefers” has been proposed to refer the lines of equal deformation. Isodefers are also a significant tool for practicing engineers to understand vertical deformation distribution below a uniformly loaded square area and estimate drag forces on nearby deep foundations. A case study emerging from similar real life scenario has also been analyzed and results are discussed with suitable recommendations.

Solo grampeado é uma alternativa eficiente utilizada em obras de reforço de solos. É resultante da inclusão de reforços, denominados grampos, em um maciço em corte. A resistência ao cisalhamento da interface solo-grampo é um dos parâmetros mais importantes para fins de projeto. Este parâmetro é determinado a partir da experiência dos projetistas e se baseia principalmente no tipo de solo e em ensaios de campo (arrancamento, sondagens a percussão e pressiométricos). Neste contexto, a realização de ensaios de arrancamento in situ é extremamente importante para a quantificação deste parâmetro e, conseqüentemente, para a elaboração de projetos mais econômicos e seguros. A execução de ensaios de arrancamento em laboratório permite verificar condições muitas vezes não encontradas em campo. Este trabalho apresenta os resultados de ensaios de arrancamento de grampos realizados em laboratório. Também foi analisada a evolução da força nos grampos e dos deslocamentos do solo. Os grampos foram instalados em um protótipo de solo grampeado sobre o qual se aplicou uma sobrecarga de 50 kPa através de uma bolsa de ar comprimido. Os ensaios de arrancamento permitiram quantificar valores de resistência ao cisalhamento de interface da ordem de 145 kPa, mobilizados com pequenos deslocamentos dos grampos. O arrancamento de grampos instrumentados indicou que cerca de 90% do comprimento total dos grampos foi solicitado. Ao final dos ensaios de arrancamento, os grampos foram extraídos completamente do maciço de solo o que permitiu comprovar a sua integridade física. Os deslocamentos do solo foram máximos próximo ao topo do protótipo e na direção horizontal. Os resultados demonstram a viabilidade de estudar o comportamento do maciço reforçado a partir do comportamento do protótipo de solo grampeado construído em laboratório. / Soil nailing is an efficient soil reinforcement technique which uses inclusions, namely nails, in soil slopes. Unit skin friction is one of the most important parameters used in soil nailing design. The definition of this parameter is commonly based on local experience and correlations to some in situ tests. This work presents the results obtained from the pullout test carried out in a soil nailed wall prototype built in laboratory. Forces acting in nails were measured by strain gage instrumentation. Soil displacement was measured in short and long terms. The pullout tests were carried out after the application of a uniform surcharge given by a compressed air bag. The results showed that unit skin friction was about 145 kPa, mobilized with little nail displacements. About 90% of nail length were solicited during pullout tests, according to tests performed in strain gage instrumented nails. Nail extraction showed a high level of nail integrity. Soil displacements were higher close to the wall top, near the face. These results demonstrate the feasibility of using of laboratory prototype studies to investigate the geotechnical behavior of soil nailing structures.

Dentre as técnicas de reforço de solos, o solo grampeado têm se destacado em âmbito mundial devido a sua versatilidade e eficiência na estabilização de taludes de escavação por meio do reforço do solo \"in situ\", através da introdução de gramposno meio a ser estabilizado. A resistência ao cisalhamento na interface solo-grampo é um dos parâmetros mais importantes a serem analisados. Esta pode ser obtida por meio de ensaios de arrancamento. No entanto, como estes ensaios devem serexecutados durante a execução das obras, existe uma grande aplicação de estimativas da resistência por atrito lateral, baseada em correlações empíricas. Este trabalho realiza a previsão da resistência ao cisalhamento da interface solo-calda quefoi avaliada experimentalmente por meio de ensaios de cisalhamento direto realizados em laboratório. Estes ensaios permitiram uma análise dos parâmetros de resistência dos solos (c e \'fi\') e das interfaces solo-calda. Adicionalmente, foramelaborados traços alternativos de caldas solo-cimento de modo a avaliar sua aplicabilidade na técnica de solo grampeado. Os resultados permitiram constatar que o uso de solo-cimento em substituição a calda de cimento convencional é viável, vistoque os resultados apresentaram um ganho de resistência ao cisalhamento de interface. Os valores de resistência de interface obtida em laboratório apresentaram resultados próximos aos valores de campo, obtidos a partir da realização dos ensaiosde arrancamento em obras distintas. / Among the techniques to enhance soil, the nailing soil have been highlighted in the world due to its versatility and efficiency in the stabilization of excavation\'s slopes by means of the strengthening of the soil in situ by the introduction ofnails in the environment that it wanted to stabilize. The shear strength at the interface soil-nailed is one of the most important parameters to be analyzed. This can be obtained by pullout testing. However, these tests should be performedduring the construction activities, there is a great application of estimates of resistance by lateral friction, based on empirical correlations. This study evaluates the prediction of the strength to shear in the soil-grout interface which was experimentally evaluated by means of direct shear tests performed in the laboratory. These tests allowed an analysis of the parameters of resistance of the soils and of the soil-grout interfaces. Additionally, it was developed alternative batches of soil-cement grouts to assess its applicability in the technique of soil nailing. The outcomes allowed conclude to the use of soil-cement in place of the conventional cement grout is feasible, because the results presented aconsiderable gain in shear strength of interface. The values resistance of the interface obtained in the laboratory showed similar results to the values of the field, obtained from the pullout testing in different construction sites.

Trends in the construction of deep excavations include deeper excavations situated closer to buildings. This research provides insight into mechanisms of soil-structure interaction for piled buildings adjacent to deep excavations to be used in the design and monitoring of deep excavations in urban areas. Most methods to assess building response have originally been developed for tunnelling projects or buildings with shallow foundations. Monitoring data of the construction of three deep excavations for the North South metro Line in Amsterdam, The Netherlands have been used to validate these methods specifically for piled buildings. In all three of the Amsterdam deep excavations studied, the largest impact on the ground surface and buildings is attributed to preliminary activities instead of the commonly expected excavation stage. The in situ preliminary activities caused 55-75% of the surface settlement and 55-65% of the building settlements. Surface settlements measured behind the wall were much larger than the wall deflections and reached over a distance of 2-3 times the excavated depth away from the wall. The shape of the surface settlements found resembles the hogging shape as defined by Peck (1969). For the excavation stage only, the shape of the displacement fits the profile proposed by Hsieh and Ou (1998). Most prediction methods overestimate the soil displacement at depth. An analytical method has been established and tested for the behaviour of piled buildings near excavations. This method includes the reduction of pile capacity due to lower stress levels, settlement due to soil deformations below the base of the pile and development of negative (or positive) skin friction due to relative movements of the soil and the pile shaft. The response of piles in the case of soil displacements depends on the working load of the pile, the percentages of end bearing and shaft friction of the pile, the size and shape of the soil settlements with depth and the distribution of the maximum shaft friction with depth. A method is derived to determine the level for each pile at which the pile and soil settlement are equal. Buildings in Amsterdam built before 1900 and without basement are most sensitive to soil displacements. For all other buildings, the pile settlement depends mainly on the working load. The actual damage experienced in buildings depends also on the relative stiffness of the building compared to the soil. Cross sections in Amsterdam have been evaluated and it is concluded that the Goh and Mair (2011) method provides a realistic, although rather large range of possible modification factors for the deflection of buildings next to excavations, deforming in hogging shape. For the incidents that happened at Vijzelgracht some well known damage indicators have been evaluated.

Dentre as técnicas de reforço de solos, o solo grampeado têm se destacado em âmbito mundial devido a sua versatilidade e eficiência na estabilização de taludes de escavação por meio do reforço do solo \"in situ\", através da introdução de gramposno meio a ser estabilizado. A resistência ao cisalhamento na interface solo-grampo é um dos parâmetros mais importantes a serem analisados. Esta pode ser obtida por meio de ensaios de arrancamento. No entanto, como estes ensaios devem serexecutados durante a execução das obras, existe uma grande aplicação de estimativas da resistência por atrito lateral, baseada em correlações empíricas. Este trabalho realiza a previsão da resistência ao cisalhamento da interface solo-calda quefoi avaliada experimentalmente por meio de ensaios de cisalhamento direto realizados em laboratório. Estes ensaios permitiram uma análise dos parâmetros de resistência dos solos (c e \'fi\') e das interfaces solo-calda. Adicionalmente, foramelaborados traços alternativos de caldas solo-cimento de modo a avaliar sua aplicabilidade na técnica de solo grampeado. Os resultados permitiram constatar que o uso de solo-cimento em substituição a calda de cimento convencional é viável, vistoque os resultados apresentaram um ganho de resistência ao cisalhamento de interface. Os valores de resistência de interface obtida em laboratório apresentaram resultados próximos aos valores de campo, obtidos a partir da realização dos ensaiosde arrancamento em obras distintas. / Among the techniques to enhance soil, the nailing soil have been highlighted in the world due to its versatility and efficiency in the stabilization of excavation\'s slopes by means of the strengthening of the soil in situ by the introduction ofnails in the environment that it wanted to stabilize. The shear strength at the interface soil-nailed is one of the most important parameters to be analyzed. This can be obtained by pullout testing. However, these tests should be performedduring the construction activities, there is a great application of estimates of resistance by lateral friction, based on empirical correlations. This study evaluates the prediction of the strength to shear in the soil-grout interface which was experimentally evaluated by means of direct shear tests performed in the laboratory. These tests allowed an analysis of the parameters of resistance of the soils and of the soil-grout interfaces. Additionally, it was developed alternative batches of soil-cement grouts to assess its applicability in the technique of soil nailing. The outcomes allowed conclude to the use of soil-cement in place of the conventional cement grout is feasible, because the results presented aconsiderable gain in shear strength of interface. The values resistance of the interface obtained in the laboratory showed similar results to the values of the field, obtained from the pullout testing in different construction sites.

Accurate measurement of skin friction in complex flows is important for: documentation and monitoring of fluid system performance, input information for flow control, development of turbulence models and CFD validation. The goal of this study was to explore using new materials to directly measure skin friction in a more convenient way than available devices. Conventional direct measurement skin friction sensors currently in use are intrusive, requiring movable surface elements with gaps surrounding that surface, or require optical access for measurements. Conventional direct measurement sensors are also difficult to apply in low shear environments, in the 1-10 Pa range. A new thin, flexible, nanoparticle infused, piezoresistive material called Metal Rubber" was used to create sensors that can be applied to any surface. This was accomplished by using modern computerized finite element model multiphysics simulations of the material response to surface shear loads, in order to design a sensor configuration with a reduced footprint, minimal cross influence and increased sensitivity. These sensors were then built, calibrated in a fully-developed water channel flow and tested in both the NASA 20x28 inch Shear Flow Control Tunnel and a backwards facing step water flow. The results from these tests showed accurate responses, with no amplification to the sensor output, to shear levels in the range of 1-15 Pa. In addition, the computer model of these sensors was found to be useful for studying and developing refined sensor designs and for documenting sources of measurement uncertainty. These encouraging results demonstrate the potential of this material for skin friction sensor applications. / Ph. D.

This work is concerned with the study of flow stability and turbulence control - two old but still open problems of fluid mechanics. The topics are distinct and are (currently) approached from different directions and with different strategies. This thesis reflects this diversity in subject with a difference in geometry and, consequently, flow structure: the first problem is approached in the study of the flow in a toroidal pipe, the second one in an attempt to reduce the drag in a turbulent channel flow. The flow in a toroidal pipe is chosen as it represents the common asymptotic limit between spatially developing and helical pipes. Furthermore, the torus represents the smallest departure from the canonical straight pipe flow, at least for small curvatures. The interest in this geometry is twofold: it allows us to isolate the effect of the curvature on the flow and to approach straight as well as helical pipes. The analysis features a characterisation of the steady solution as a function of curvature and the Reynolds number. The problem of forcing fluid in the pipe is addressed, and the so-called Dean number is shown to be of little use, except for infinitesimally low curvatures. It is found that the flow is modally unstable and undergoes a Hopf bifurcation that leads to a limit cycle. The bifurcation and the corresponding eigenmodes are studied in detail, providing a complete picture of the instability. The second part of the thesis approaches fluid mechanics from a different perspective: the Reynolds number is too high for a deterministic description and the flow is analysed with statistical tools. The objective is to reduce the friction exerted by a turbulent flow on the walls of a channel, and the idea is to employ a control strategy independent of the small, and Reynolds number-dependent, turbulent scales. The method of choice was proposed by Schoppa &amp; Hussain [Phys. Fluids 10:1049-1051 (1998)] and consists in the imposition of streamwise invariant, large-scale vortices. The vortices are re-implemented as a volume force, validated and analysed. Results show that the original method only gave rise to transient drag reduction while the forcing version is capable of sustained drag reduction of up to 18%. An analysis of the method, though, reveals that its effectiveness decreases rapidly as the Reynolds number is increased. / <p>QC 20161004</p>

Many existing boundary layer models treat transition as a rapid switch from laminar to turbulent flow, with correlations defining properties in each respective region. Natural transition, however, is not always a very spanwise uniform process, with the onset of transition varying somewhat between different streamwise paths of fluid flow. Thus, a spanwise average of natural transition can result in a more gradual, extended transition region than many existing models predict. Modern applications, such as aircraft wings and fuselages, are extremely streamlined and smooth, allowing for natural transition to occur rather than flow tripping to turbulent near the leading edge. Under these conditions, a skin friction model that takes this extended transition region into account provides a more accurate model compared to those which incorporate a rapid transition from laminar to turbulent flow. Lienhard’s recent publication 1 presents a new rationale for modeling the extent of the transition region on a smooth flat plate developed from re-analysis of existing heat transfer data. This correlation accounts for the extended natural transition region corresponding to a spanwise average of values. The primary objective of this thesis was to reinterpret Lienhard’s heat transfer correlation to solve for skin friction coefficient, then compare this correlation to available experimental data and higher order boundary layer models. After reinterpreting Lienhard’s correlation using the Reynolds analogy, it produced a gradual, extended transition region for skin friction coefficient. The reinterpreted correlation had excellent agreement with experimental data corresponding to a spanwise average of flow with natural transition. Tripped transitional values and data taken along a streamwise path of fluid resulted in a more rapid transition from laminar to turbulent flow. Both an integral boundary layer model and a Reynolds-averaged Navier-Stokes boundary layer model were used to validate the reinterpreted Lienhard correlation. Both of these models produced transition curves steeper than the reinterpreted Lienhard curve. These existing boundary layer models do not take into account the gradual transition region that natural transition may produce when looking at a spanwise average of values. With a focus on spanwise averaged values, such as overall drag over a streamlined surface, existing sophisticated boundary layer models may not accurately predict the behavior produced. The reinterpreted Lienhard correlation provides a new representation of skin friction coefficient throughout the boundary layer that takes into account the extended transition region that may occur when it is desired to model a spanwise average of fluid flow. 1Lienhard, J. Heat transfer in flat-plate boundary layers: A correlation for laminar, transitional, and turbulent flow. ASME Journal of Heat Transfer, 142, 2020.

This thesis discusses a comparison of the differences in aerodynamic performance of wings designed with elliptical and bell-shaped lift distributions. The method uses a Standard Cirrus sailplane wing with a lift distribution associated with the induced drag benefits of an elliptical distribution (span efficiency = 0.96) as the basis of comparison. The Standard Cirrus is a standard class sailplane with 15-meter wingspan that was designed by Schempp-Hirth in 1969. This sailplane wing was modeled and analyzed in XFLR5, then validated against existing wind tunnel airfoil data, and Standard Cirrus flight test data. The root bending moment of the baseline wing was determined and used as the primary constraint in the design of two wings with bell-shaped lift distribution. These wings were modeled in XFLR5 by adjusting chord length and geometric twist respectively, and then they were studied using fixed speed lifting line analysis. Steady state cruise conditions for the Standard Cirrus sailplane were taken from the flight test data and applied for the analysis. The wing designed with chord variation posed incompatibilities with the lifting line method. The resulting planform was strongly tapered in the wingtip region and the reference chord length there was such that the software could not solve for a Reynolds number the magnitude resulting from two-dimensional airfoil analysis. However, the wing geometry provided insight into the design aspect of wings with bell-shaped lift distribution. Using chord variation to shape the lift distribution, the wing featured a 12% increase in wingspan but a 6.5% decrease in total wetted area when compared to the baseline. The results of the analysis of the wing designed with geometric twist indicate that induced drag decreased by 5% when compared to the baseline wing. The constraint on root bending moment resulted in a 12% increase in wingspan. Wetted area also increased by 14.8% over the baseline yielding an estimated 15% increase in skin friction.

Turbulent boundary layers over rough surfaces are a common, yet often overlooked, problem of practical engineering importance. Development of correlations between boundary layer parameters that can be used in turbulence models and the surface geometry is the only practical option for solving these problems. Experiments have been performed on a two-dimensional zero pressure gradient turbulent boundary layer over sparsely spaced hemispherical roughness elements of 2 mm diameter. Laser Doppler velocimetry was used to measure all three components of velocity. The friction velocity was calculated using an integral momentum balance. Comparisons were made with various fitting methods that assume the von Kármán constant is appropriate for rough walls. Results indicate that this is not the case, and that the slope of the semi-logarithmic portion of the mean streamwise profile may be a function of the ratio of inner and outer length scales. Comparisons were also made between various correlations that relate the surface geometry to the behavior of the mean velocity profile. In general, the existing correlations achieved a reasonable agreement with the data within the estimated uncertainties. A detailed study of the local turbulent structure around the roughness elements was performed. It was found that, in contrast to `sharper-edged' elements such as cylinders, an elevated region of TKE and Reynolds shear stress was found downstream of the element below the peak. This can be explained by the delay in separation of the flow coming over the top of the element due to the smooth curvature of the element. Surface pressure fluctuation measurements were made as well using a dual microphone noise reduction technique. There have only been a few past experiments on the surface pressure fluctuations under rough wall boundary layers. However, it has been shown that the spectra of the wall fluctuations can be used to predict the far-field noise spectrum [1,2]. Therefore it is been the goal of this research to verify existing correlations between the surface pressure fluctuation spectrum and the surface geometry as well as develop new correlations that provide insight into the interactions between the turbulent motions in the flow surface pressure. / Ph. D.