Scour is the leading cause of bridge failure in the United States. It is the result of the erosive action of flowing water excavating and carrying away material from the beds and/or banks of streams. To ensure public safety and minimize potential bridge damage caused by scour, a countermeasure is incorporated at a stream or bridge crossing system to monitor, control, inhibit, change, delay, or minimize stream and bridge stability problems, including scour. Countermeasures can be installed at the time of construction for new bridges or can be retrofitted to existing bridges when stability issues arise. Riprap is the most commonly used countermeasure for scour protection. It is the most understood, studied and documented of all the countermeasures. In addition to basic, loose riprap, partially grouted riprap (PGR) is also an option when selecting a countermeasure. PGR is relatively new in the United States, but has been used widely in Europe to prevent scour or erosion of the bed, banks, shoreline, and at piers and abutments. PGR construction involves placement of specifically sized riprap on top of granular filters or geotextile filter and/or a combination of both filters. A high slump Portland cement based grout is used to interlock the riprap by partially filling one-third to one-half of the total void space of the original riprap. Grouting is done in the dry or in the wet by hose or by automated mechanical means. Turbidity and pH level are the main problems when using grouting. Currently in Pennsylvania, the selection of appropriate countermeasures and the design for bridge foundation protection against scour have in general been restricted in their applications to mainly dumped riprap, which can be displaced after each flood. Similar to Hydraulic Engineering Circular No. 23 (HEC 23), Abboud et al. (1) developed a set of matrices that are used as guidelines for scour countermeasure selection for the State of Pennsylvania. Abboud et al. (1) also developed design guidelines for the recommended scour countermeasures. Partially grouted riprap was considered by Abboud et al. (1) as vital countermeasure to control scour at Pennsylvania bridge abutments and piers. Based on guidance developed by Federal Waterway Engineering and Research Institute (BAW) in Germany, HEC 23 Design Guidelines 12 "Partially Grouted Riprap at Bridge Piers" provided general requirements for grouting materials and standard European testing for grout quality and consistency. Hence, there is a critical need to develop guidelines to select grout design mix that minimize the environmental impact and to utilize current US standards to control the grout design mix for the construction in the dry and in the wet. An experimental research study was established in this research program to develop general requirements for grouting materials for partially grouting riprap "in the wet" and "in the dry" that can be used in the scour countermeasure construction of partially grouted riprap at scour critical bridges in the state of Pennsylvania. The research program intended to utilize current US standards to evaluate grout quality and consistency. In this experimental research, a number of grout quality control tests were conducted and a correlation between the European Flow Table Test and ASTM C 1611"Standard Test Method for Slump of Self-Consolidating Concrete" was established. Recommendations for grout mix design for construction in the wet and in the dry is presented with general guidance of grouting materials for the design guidelines of partially grouted riprap for piers and abutment. / Civil Engineering

No description available.

Neste trabalho se avaliou experimentalmente o comportamento de um sistema de emenda de barra que transmitisse de forma mais eficiente os esforços solicitantes. A emenda consistiu-se de um tubo de aço preenchido com graute de alta resistência à compressão e duas barras de aço, uma em cada extremidade com o mesmo comprimento de embutimento. Esta emenda foi submetida a ações monotônicas e cíclicas de tração axial, com controle de deslocamento até atingir a ruptura, verificando a capacidade última da emenda e seus modos de ruína. No programa experimental foram ensaiadas emendas sendo que foram levados em consideração os seguintes parâmetros: o diâmetro da barra, o diâmetro do tubo, a conformação superficial do tubo, o tipo de carregamento, o cobrimento, o comprimento de embutimento e a posição da barra. A ruptura das emendas ocorreu por escoamento da barra de aço, fendilhamento e escorregamento da barra em relação ao graute; conforme o diâmetro da barra e a conformação superficial interna do tubo. Ainda, verificou-se que este tipo de emenda garante uma adequada transferência de esforços de tração. A corrugação do tubo teve influência significativa, uma vez que a sua falta levou ao escorregamento da barra em relação ao graute, bem como o comprimento de embutimento insuficiente levou à ruptura do graute; a posição da barra não teve influência significativa. / The main purpose of this research was to analyze experimentally the behavior of a splicing system with a grout-filled steel tube and reinforced bar to transmit the efforts efficiently. A splice was prepared with a grout-filled steel tube and two reinforced bars, one in each end of the tube with the same anchorage length. The splices were loaded in monotonic and ciclic axial tension until failure, with displacements control, measuring the maximum load and observing the splicing failure mode. An experimental program was carried out and adopted as variables the bar diameter, the tube diameter, the type of internal surface of the tube, the loading, coverage, lenght anchorage and the bar position. The failure of the splice occurred by yielding bar failure, grout splitting and grout slipping, according to the bar diameter and the internal surface of the tube. It was verified that this type of splice guarantees a good efforts transmission. The ribs inside the tube had significant influence, while the failure occurred by the grout slipping without the tube ribbed; the bar position had not significant influence.

Construction practices are constantly evolving in order to adapt to physical locations and economic conditions. These adaptations may result in more cost-effective designs, but may also come at a cost of strength. In masonry shear walls, it is becoming more common to reduce the amount of grouting from every cell to only those with reinforcement, a practice known as partial-grouting. Partially-grouted masonry responds differently and in a more complex matter to lateral loads as compared to fully-grouted masonry. The response is made even more complex by wall discontinuities in the form of openings. The main objective of this study is to validate the strut-and-tie procedure for the in-plane lateral strength prediction of partially-grouted, multistory, reinforced concrete masonry walls with openings. The research included testing six three story, half-scale masonry shear walls. Half of the walls had door openings while the other half had window openings. The configurations were selected to represent typical walls in multi-story buildings. The measured lateral strength was compared to estimations from the equations in the US masonry code and to those from an equivalent truss model and a strut-and-tie model. The results show that the U.S. masonry code equations over predicts while the equivalent truss model under predicts the lateral strength of the walls. The results further show that the strut-and-tie model is the most accurate method for lateral strength prediction and is able to account for wall openings and partial-grouting.

Neste trabalho se avaliou experimentalmente o comportamento de um sistema de emenda de barra que transmitisse de forma mais eficiente os esforços solicitantes. A emenda consistiu-se de um tubo de aço preenchido com graute de alta resistência à compressão e duas barras de aço, uma em cada extremidade com o mesmo comprimento de embutimento. Esta emenda foi submetida a ações monotônicas e cíclicas de tração axial, com controle de deslocamento até atingir a ruptura, verificando a capacidade última da emenda e seus modos de ruína. No programa experimental foram ensaiadas emendas sendo que foram levados em consideração os seguintes parâmetros: o diâmetro da barra, o diâmetro do tubo, a conformação superficial do tubo, o tipo de carregamento, o cobrimento, o comprimento de embutimento e a posição da barra. A ruptura das emendas ocorreu por escoamento da barra de aço, fendilhamento e escorregamento da barra em relação ao graute; conforme o diâmetro da barra e a conformação superficial interna do tubo. Ainda, verificou-se que este tipo de emenda garante uma adequada transferência de esforços de tração. A corrugação do tubo teve influência significativa, uma vez que a sua falta levou ao escorregamento da barra em relação ao graute, bem como o comprimento de embutimento insuficiente levou à ruptura do graute; a posição da barra não teve influência significativa. / The main purpose of this research was to analyze experimentally the behavior of a splicing system with a grout-filled steel tube and reinforced bar to transmit the efforts efficiently. A splice was prepared with a grout-filled steel tube and two reinforced bars, one in each end of the tube with the same anchorage length. The splices were loaded in monotonic and ciclic axial tension until failure, with displacements control, measuring the maximum load and observing the splicing failure mode. An experimental program was carried out and adopted as variables the bar diameter, the tube diameter, the type of internal surface of the tube, the loading, coverage, lenght anchorage and the bar position. The failure of the splice occurred by yielding bar failure, grout splitting and grout slipping, according to the bar diameter and the internal surface of the tube. It was verified that this type of splice guarantees a good efforts transmission. The ribs inside the tube had significant influence, while the failure occurred by the grout slipping without the tube ribbed; the bar position had not significant influence.

Concrete masonry is a multi-component structural system. In the case of reinforced concrete masonry, the system includes the concrete units, the mortar, the reinforcing steel and the grout fill. Placing vertical steel reinforcing bars in the cores of the concrete units enhances the flexural strength of the wall. The vertical steel, when subjected to compression at moderate strain levels, must be confined to improve its resistance to buckling and to improve the effectiveness of the grout around the reinforcing bar. Based on the well established behaviour of reinforced concrete systems, it seems reasonable to presume that the primary means of enhancing ductility is to provide lateral confining steel at closely-spaced intervals to effectively increase the ultimate compressive strain in the grout. It may be assumed that transverse reinforcement in concrete masonry provides lateral confinement to the core so that the axial compressive strength of the grout is enhanced and the ductility improved. <p>The focus of this study was to investigate the effect of vertical reinforcement and lateral confinement on the axial capacity of short partially grouted concrete masonry walls built in running bond. In order to better understand the structural behaviour of both confined and unconfined concrete masonry, it is important to have some knowledge of the load-displacement behaviour, stress-strain behaviour and failure modes of the masonry walls with different configurations of vertical and lateral reinforcement. <p>An experimental study was performed to investigate the behaviour of partially grouted concrete masonry block walls under axial loading. Three types of test specimens of partially grouted concrete block masonry walls were tested: <p>(1) specimens with a grouted core only; <p>(2) specimens with a grouted core and vertical reinforcement (i.e. no confinement); and <p>(3) specimens with a grouted core, vertical reinforcement and spiral confinement in the grouted cores. In total, thirty short wall specimens were tested to failure. <p>The structural behaviour of vertically reinforced, laterally confined walls was compared to vertically reinforced, unconfined walls, as well as to unreinforced, unconfined masonry walls. The test results indicated that vertical reinforcement of the grouted core did not have a significant positive effect on the failure modes and strength of the short masonry walls. Due to problems with adequate compaction, the lateral confinement provided by the spiral reinforcement had a slightly negative effect on the compressive strength of concrete masonry walls built in running bond. Vertical reinforcement and lateral confinement of the grouted core had some positive effect on the ductility. From a comparison of the ductility for all three types of specimens it was found that both the vertical reinforcement and lateral confinement of the core had a beneficial influence on the post-peak ductility. <p>In general, similar crack patterns and failure modes were observed in all three types of specimens. Vertical cracks that progressed through the end faces of the concrete blocks and mortar joints, suggesting that the lateral expansion of the grouted core contributed to tensile splitting stresses in walls. All walls failed in a compression-tension stress state, which featured spalling away of the block shells and vertical tensile splitting on the end faces.

Concrete masonry is a multi-component structural system. In the case of reinforced concrete masonry, the system includes the concrete units, the mortar, the reinforcing steel and the grout fill. Placing vertical steel reinforcing bars in the cores of the concrete units enhances the flexural strength of the wall. The vertical steel, when subjected to compression at moderate strain levels, must be confined to improve its resistance to buckling and to improve the effectiveness of the grout around the reinforcing bar. Based on the well established behaviour of reinforced concrete systems, it seems reasonable to presume that the primary means of enhancing ductility is to provide lateral confining steel at closely-spaced intervals to effectively increase the ultimate compressive strain in the grout. It may be assumed that transverse reinforcement in concrete masonry provides lateral confinement to the core so that the axial compressive strength of the grout is enhanced and the ductility improved. <p>The focus of this study was to investigate the effect of vertical reinforcement and lateral confinement on the axial capacity of short partially grouted concrete masonry walls built in running bond. In order to better understand the structural behaviour of both confined and unconfined concrete masonry, it is important to have some knowledge of the load-displacement behaviour, stress-strain behaviour and failure modes of the masonry walls with different configurations of vertical and lateral reinforcement. <p>An experimental study was performed to investigate the behaviour of partially grouted concrete masonry block walls under axial loading. Three types of test specimens of partially grouted concrete block masonry walls were tested: <p>(1) specimens with a grouted core only; <p>(2) specimens with a grouted core and vertical reinforcement (i.e. no confinement); and <p>(3) specimens with a grouted core, vertical reinforcement and spiral confinement in the grouted cores. In total, thirty short wall specimens were tested to failure. <p>The structural behaviour of vertically reinforced, laterally confined walls was compared to vertically reinforced, unconfined walls, as well as to unreinforced, unconfined masonry walls. The test results indicated that vertical reinforcement of the grouted core did not have a significant positive effect on the failure modes and strength of the short masonry walls. Due to problems with adequate compaction, the lateral confinement provided by the spiral reinforcement had a slightly negative effect on the compressive strength of concrete masonry walls built in running bond. Vertical reinforcement and lateral confinement of the grouted core had some positive effect on the ductility. From a comparison of the ductility for all three types of specimens it was found that both the vertical reinforcement and lateral confinement of the core had a beneficial influence on the post-peak ductility. <p>In general, similar crack patterns and failure modes were observed in all three types of specimens. Vertical cracks that progressed through the end faces of the concrete blocks and mortar joints, suggesting that the lateral expansion of the grouted core contributed to tensile splitting stresses in walls. All walls failed in a compression-tension stress state, which featured spalling away of the block shells and vertical tensile splitting on the end faces.

Grouting techniques have been in used for many years, but several new grout materials have surfaced in recent decades that have re-defined the boundaries of the limitations of grouting programs. Typically these applications are used for seepage control in earthen impoundments, but strength of these earthen impoundments should be considered where there is potential for movement in the grouted soil mass. This study investigated initial conditions that could affect grout application effectiveness. The initial conditions in question were soil grain size and in situ moisture content. Two grouts were used, ultrafine and acrylate, and variations in pure grout properties were studied. An apparatus was developed so that a uniform grout could penetrate the pore spaces of a soil specimen. The rate of penetration of the grout into the soil was studied. The unconfined compressive strength of the resulting grouted soil was then analyzed. In testing neat ultrafine grout, it was shown that increased water-to-cement ratios had negative effects on the stability of the grout. Increasing the water-to-cement ratio from 0.5 to 2.5 resulted in a decrease in strength by a factor of 100. An inhibitor chemical was used to increase the time for reaction in the acrylate grout. During the chemical reaction, the curing temperature and gel times were monitored. A grout mix was selected for the acrylate grout that achieved appropriate gel times. In general, this study found that the grout penetrations rates into the soil increased as the initial moisture was increased from dry conditions to a gravimetric moisture content of nine percent. In each study, increased initial moisture decreased the grouted soil strength, with decreases in strength exceeding 50 percent. Empirical relationships were realized when compared to the initial matric suction of the soil. This suggests initial matric suction may be a useful initial condition for estimating increases in soil strength upon implementation of a grouting program for both the acrylate and ultrafine grouts.

Magíster en Ciencias, Mención Geología / Una de las principales variables que necesitan ser manejadas apropiadamente en minas a cielo abierto es la presión de poro generada detrás de los taludes, ya que disminuye la resistencia al corte del suelo. El trabajo de diseño analítico y numérico para taludes ha utilizado tradicionalmente el nivel freático como entrada para los modelos geotécnicos, asumiendo implícitamente condiciones hidrostáticas en profundidad. Esta simplificación contrasta con la realidad del entorno minero, en especial en grandes minas a cielo abierto y en operaciones con programas activos de despresurización, en las que los gradientes hidráulicos verticales pueden llegar a ser importantes. En los últimos años se ha producido un avance importante en la consideración y comprensión de la hidrogeología en la mina; y cada vez es más frecuente la utilización de modelos hidrogeológicos para la obtención de las distribuciones de la presión de poro en profundidad. Sin embargo, estos modelos presentan una limitación fundamental como es la ausencia de datos suficientes para calibrarlos. Las medidas de presión de poros en la mina son en general escasas, dispersas y se limitan en el mejor de los casos, a tres o cuatro profundidades diferentes. Para hacer frente a la ausencia de datos, el proyecto Smart Open Pit Slope Management Project de CORFO entre CSIRO Chile y la U. de Chile contempla el desarrollo de una nueva herramienta de medición simultánea y en tiempo real del estado de la deformación y la presión de poros en profundidad con una densidad de muestreo hasta un orden de magnitud superior a los métodos convencionales. Disponer de datos reales de deformación y presión de poro representará una oportunidad única en términos de I+D en la comprensión del régimen de presiones hidráulicas que afectan a la estabilidad del talud de las minas y en la validación y el desarrollo de modelos geotécnicos acoplados. La integración del sensor de poros a la nueva herramienta plantea desafíos como son: asegurar que la medida es fiable, precisa, no se ve alterada por el método de instalación y proporciona información en un tiempo razonable. Todo ello sin perder de vista el contexto hidrogeológico de la variable a medir (presión de poro), sus posibles variaciones en profundidad y las dificultades que enfrenta su medición en un entorno de minería a rajo abierto en rocas de baja permeabilidad. La tesis para la obtención del magister se fundamenta en la identificación de los factores claves y las consideraciones a tener en cuenta en el desarrollo de la nueva herramienta, desde la selección e integración de los elementos y su método de instalación en sondaje, hasta una propuesta de infraestructura para llevar a cabo la instalación y las pruebas a realizar previas a su instalación en terreno.

In this study, parameters related to material properties, geometry, and external stimuli were examined individually to determine their influence on multi-story, partially grouted, perforated (openings), masonry shear walls using a finite element software FormWorks. The parameters studied were: the strength of grouted masonry prisms f'm,grouted; the strength of un-grouted (hollow) masonry prisms f'm,ungrouted; the ratio of mortar shear strength to masonry compressive strength; vertical and horizontal reinforcement ratios in terms of size and spacing of reinforcement; axial load; aspect ratio; and openings that were vertically and horizontally altered. To perform this study, finite element models were validated against the response of three experimental walls of two unique types that were built ½ scale and tested in a lab. The validated finite element models were designated as "base models" which accurately predicted the maximum strength of each wall within a tolerance of 5.9%, 3.3%, and 1.8%. Following validation, each parameter in question was varied individually to identify and quantify the sensitivity of the parameter and to observe the changes in shear capacity and deflection for this unique configuration of masonry shear walls. To capture the impact of these parameters, 38 different shear wall models were built and tested. The results were compared against the Masonry Standards Joint Committee (MSJC) (2013) code predictions using the applicable shear strength equations. Results of this study are specific to cantilever type masonry shear walls with large aspect ratios and openings in every story. Shear wall capacity was considered sensitive to the following parameters: compressive strength of grouted masonry; compressive strength of un-grouted masonry; joint strength ratio; vertical reinforcement ratio; axial stress; aspect ratio; and opening width. Shear wall capacity was considered not sensitive to the following parameters: horizontal reinforcement ratio; vertical reinforcement spacing; and horizontal reinforcement spacing. The sensitivity of shear wall capacity to opening height was determined inconclusive. The sensitivities were determined by fitting trend lines to the results of shear capacity vs. each parameter individually. Each MSJC (2013) code prediction un-conservatively over-predicted the shear wall capacity except one wall configuration that had a joint strength ratio of 0.045.