Thesis EFECTO DEL TAMAÑO DE LA PROBETA EN LA ENERGIA DISIPADA DE LOS HRF DETERMINADA MEDIANTE EL ENSAYO BARCELONA
Date
2019
Authors
AHUMADA ÁLVAREZ, MATÍAS IGNACIO FRANCISCO
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Abstract
En los últimos años, los hormigones proyectados o shotcrete reforzados con fibras (SFR) están siendo ampliamente utilizados para el revestimiento de túneles, especialmente en proyectos hidroeléctricos y faenas mineras. En esos proyectos, los diseños de los sostenimientos se basan principalmente en el método Q-Barton modificado, el que relaciona la calidad del macizo rocoso con la capacidad de absorción de energía requerida del SRF, la que se determina mediante el ensayo de paneles cuadrados, siguiendo las recomendaciones dadas por EFNARC en 1996.Sin embargo, esta prueba requiere probetas de gran tamaño y peso, que deben ser llenadas durante la proyección del SRF en el túnel. Esto a menudo hace que el panel presente defectos o daños que alteran los resultados, aumentando la dispersión, con coeficientes de variación entre probetas de la misma muestra superior al 20%. Adicionalmente, el uso de paneles para el control de calidad de los SFR no permite verificar la calidad del sostenimiento resultante, así como tampoco volver a ensayar el SRF de un punto dudoso. Debido a esto, diferentes autores han considerado que este ensayo no es adecuado para el control de calidad del SRF en obra, lo que ha motivado al uso del ensayo de tracción indirecta por doble punzonamiento o “ensayo Barcelona (BCN).El ensayo Barcelona normalizado considera el uso de probetas cilíndricas de 150 mm de diámetro y 150 mm de altura. Sin embargo, algunos espesores del shotcrete son menores a 150 mm.El tema principal de la presente memoria, es establecer una equivalencia entre la energía disipada por el SFR cuantificada mediante el ensayo Barcelona normalizado y en testigos de 100 mm de diámetro y altura, luego relacionar estos valores con la capacidad de absorción de energía determinada mediante el ensayo de panel cuadrado EFNARC.Para tal objetivo, se realiza una campaña experimental en la que se ensayaran paneles y testigos de 150 mm de diámetro, con dosificación diseñada para uso en shotcrete reforzada con 4 y 5 kg de fibra por metro cubico de hormigón. Después de ensayados los paneles, se extraerán probetas de 100 mm de diámetro de las zonas fracturadas de cada uno de ellos, las cuales se someterán al ensayo BarcelonaDe esta forma, usando los resultados experimentales, se propondrán equivalencias que permitan relacionar la energía disipada obtenida con el ensayo Barcelona con cilindros de 150 mm y 100 mm y a su vez con los paneles EFNARC.
In recent years, projected concretes or fiber reinforced shotcrete (FRS) are being used for floor covering, especially in hydroelectric projects and mining operations. In these projects, the designs of the tunnel support are based mainly on the modified Q-Barton method, which relates the quality of the rock mass with the required energy absorption capacity of the FRS, which is determined by the square panels test, following the recommendations given by EFNARC in 1996.However, this test requires large size and weight probes, which must be filled during the FRS projection in the tunnel. This often causes the panel to present defects or damages that alter the results, increasing the dispersion, with coefficients of variation between the probes of the same sample higher than 20%. Additionally, the use of panels for the quality control of the FRSs does not allow to verify the quality of the resulting support, or to re-test the SRF of a doubtful point. Due to this, different authors have considered that this test is not suitable for the quality control of SRF in the work, which has motivated the use of the indirect technique test for the double punching of the Barcelona test (BCN).The Barcelona standardized test considers the use of cylindrical test tubes of 150 mm in diameter and 150 mm in height. However, some thicknesses of the shotcrete are less than 150 mm.The main theme of this report is to establish an equivalence between the energy dissipated by the SFR quantified by the standardized Barcelona test and in the 100 mm diameter and height controls, then relate these values to the specific energy absorption capacity by means of the square panel test EFNARC.For this purpose, an experimental campaign was carried out in which panels and test pieces of 150 mm diameter were tested, with dosing designed for use in reinforced shotcrete with 4 and 5 kg of fiber per cubic meter of concrete. After testing the panels, samples of 100 mm diameter were extracted from the fractured areas of each of them, which will be submitted to the Barcelona testIn this way, using the experimental results, equivalences will be proposed that allow to relate the dissipated energy obtained with the Barcelona test with cylinders of 150 mm and 10 mm and in turn with the EFNARC panels.
In recent years, projected concretes or fiber reinforced shotcrete (FRS) are being used for floor covering, especially in hydroelectric projects and mining operations. In these projects, the designs of the tunnel support are based mainly on the modified Q-Barton method, which relates the quality of the rock mass with the required energy absorption capacity of the FRS, which is determined by the square panels test, following the recommendations given by EFNARC in 1996.However, this test requires large size and weight probes, which must be filled during the FRS projection in the tunnel. This often causes the panel to present defects or damages that alter the results, increasing the dispersion, with coefficients of variation between the probes of the same sample higher than 20%. Additionally, the use of panels for the quality control of the FRSs does not allow to verify the quality of the resulting support, or to re-test the SRF of a doubtful point. Due to this, different authors have considered that this test is not suitable for the quality control of SRF in the work, which has motivated the use of the indirect technique test for the double punching of the Barcelona test (BCN).The Barcelona standardized test considers the use of cylindrical test tubes of 150 mm in diameter and 150 mm in height. However, some thicknesses of the shotcrete are less than 150 mm.The main theme of this report is to establish an equivalence between the energy dissipated by the SFR quantified by the standardized Barcelona test and in the 100 mm diameter and height controls, then relate these values to the specific energy absorption capacity by means of the square panel test EFNARC.For this purpose, an experimental campaign was carried out in which panels and test pieces of 150 mm diameter were tested, with dosing designed for use in reinforced shotcrete with 4 and 5 kg of fiber per cubic meter of concrete. After testing the panels, samples of 100 mm diameter were extracted from the fractured areas of each of them, which will be submitted to the Barcelona testIn this way, using the experimental results, equivalences will be proposed that allow to relate the dissipated energy obtained with the Barcelona test with cylinders of 150 mm and 10 mm and in turn with the EFNARC panels.
Description
Catalogado desde la version PDF de la tesis.
Keywords
ENERGIA DISIPADA , ENSAYO BARCELONA , HRF