La presente tesis responde al problema ¿Cuál es la evaluación del resultado de la aplicación del shotcrete vía seca como método de sostenimiento en el Nv. 6 – XC 750W en la Unidad Cuerpo Mery – Compañía Minera Casapalca 2017? y tiene como objetivo determinar la evaluación del resultado de la aplicación de shotcrete vía seca como método de sostenimiento en el Nv. 6 – XC 750W en la Unidad Cuerpo Mery - Compañía Minera Casapalca 2017.

Actualmente, el shotcrete es un elemento de sostenimiento usado cada vez con mayor frecuencia en la minería subterránea, Volcan Compañía Minera S.A.A. no ajeno a ello, aplica la tecnología de concreto para generar una adecuada estabilización del macizo rocoso; sin embargo, cuando este es de baja calidad (roca tipo IV A – IV B) según RMR, obliga a incrementar su dimensionamiento (sostenimiento estructural) para garantizar la estabilidad de la labor, dilatando el tiempo de instalación del sostenimiento y el ciclo de minado, generando un incremento en el costo del mismo.

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The primary aim of this research was to improve the understanding of the influence of the process and the mix constituents on the fresh and hardened properties of wetprocess sprayed mortars and concretes. The main objectives were: to improve the wetmix spraying process; to specify, measure and optimise in-situ properties; and to disseminate the information obtained in appropriate form to practising engineers to accelerate the use of wet-process sprayed mortar and concrete for repair. The research focused on three types of repair mortars/concretes: pre-blended proprietary mortars (<3 mm aggregate), designed laboratory/site batched mortars and fine concretes (<8 mm aggregate). Thirty mixes were pumped and sprayed using seven pumping/spraying systems. Nineteen types of test were conducted to measure the fresh and hardened properties using three types of specimen production (cast mould, sprayed mould and in-situ specimen). Ten repair scenarios generally encountered in the UK were identified and classified in terms of their characteristics and relevant mixes were identified to satisfy these differing requirements. A rheological audit has been developed and a variety of tests were used to characterise the pumpability and sprayability of each mix, including: rotational viscometers (Tattersall two-point test and Viskomat), pressure-bleed, shear vane, slump, build, fresh density, output, stream velocity (using high-speed video), reinforcement encasement and core grading. A new approach that defines the build in terms of the maximum shear and tensile bending stresses generated at failure was also developed. Hardened properties measured include: compressive and flexural strength, tensile bond strength, drying and restrained shrinkage, elastic modulus, air permeability, sorptivity and hardened density. The hardened performance was generally higher when sprayed with the wet process compared with hand application and lower when compared with the dry process (which was expected), although the values obtained were more than sufficient for normal repair work. All the pre-blended mortars could be pumped and sprayed with a small worm pump. Twelve laboratory-designed mortars were pumped and sprayed in a dedicated spraying chamber constructed at Loughborough and the best of these performed as well as, and produced hardened properties that equalled or surpassed, the pre-blended materials. For worm pumping the grading of a mortar was found to be important and a suitable combined material grading zone has been determined. Two pre-blended and a laboratory-designed mortar were sprayed with a piston pump as were the nine designed concrete mixes, the former producing similar in-situ properties to worm pumping. One pre-blended mix was sprayed successfully with five different wet-process pumps (four worm plus one piston) and three pre-blended mortars and one designed fine concrete were sprayed by the dry-process to benchmark performance, along with data from three repair contracts. The hardened property measurements obtained from spraying directly into steel moulds with a low-volume worm pump were consistent enough to have applications for quality control. The research demonstrated that low-volume wet spraying is a healthier, cleaner and more controllable process (compared with the dry process) which can produce consistently high quality mortars and fine concretes suitable for a range of applications in the UK.

The tunnelling industry relies heavily on the use of concrete, and most of all shotcrete. The ingredients in shotcrete and concrete are very similar, both relies on the use of cement. Cement production is one of the most energy consuming, if not the most energy consuming, industry in the business. One way of reducing the emissions of shotcrete production is to replace parts of the ingredients. Both cement and aggregates can be replaced by materials that are reused and thereby reducing emissions. Recycled aggregates are already used in construction to some extent. These recycled aggregated are usually from the demolition industry. The most effective way of reducing the carbon footprint of shotcrete is by decreasing cement levels. Fly ash and steel slag are two materials that are a suitable replacement for parts of the cement. It’s obvious that there is room for improvement, and improvement must be done. However, the reliability and consistency of many new alternative materials to cement isn’t quite there yet. It is hard to get sufficient data for these alternatives, since few big scale tests have been conducted. The life cycles of tunnels are usually very long, which makes it hard to get long time statistics for constructions with new techniques. Reducing the use of shotcrete is also something that will make a big difference on the carbon footprint. Applying shotcrete and achieving perfect results is hard, but some techniques has been developed to help the operator with the application process. Scanning is a very effective way of calibrating the operators to spray the correct thickness. Since the scanning method is still somewhat slow, scanning every single cycle is not an option today. The logistics behind shotcrete spraying is also an area that could be improved and thereby reducing the over usage of shotcrete. Replacing the current steel fibers used as reinforcement with a more sustainable material will also help reducing the carbon footprint. However, the emissions from the cement production are significantly larger. There are however other benefits with switching to synthetic fibers, mostly to do with safety of workers and machinery since synthetic fibers aren’t as sharp. These fibers are also resistant to corrosion, which makes them suitable for wet conditions. In the field tests, four different shotcrete mixes were compared and sprayed in test boxes. These mixes replaced 0, 10, 19 and 30% of the cement with steel slag. Early compressive strength was measured on all mixes and all of them achieved 10 MPa after 10 hours. At 10 hours the shotcrete mix with no steel slag, the reference concrete, accelerated its compressive strength growth. And achieved a compressive strength of 28 MPa after 17 hours. The other mixes had around 15% less compressive strength at 17 hours, but they all achieved 50% of the maximum strength within 20 hours.

Ingeniero Civil / En la presente Memoria se presenta el desarrollo y resultados de un estudio experimental de técnicas de reparación y refuerzo estructural de muros de albañilería de ladrillos confinada, dañados por efecto de sismo. La fase experimental del estudio se desarrolló en Idiem en los años 1989-90, dando origen a varias publicaciones y sirviendo sus resultados como soporte para la actualización de la Norma Chilena Oficial para albañilería confinada, NCh2123.Of1997 modificada en 2003, vigente en la actualidad. Dentro de las tipologías de muros de albañilería, el estudio se enfoca en la albañilería de ladrillos confinada, que representa al tipo más usado en Chile. Se construyeron dos series, de 6 muros cada una, de albañilería confinada de 2.4 m x 2.4 m; una serie con ladrillos hechos a máquina del tipo rejilla con huecos y la otra, con ladrillos hechos a mano, del tipo chonchón. Los muros se someten a un primer ensayo de resistencia en condición sana, siendo luego reparados y sometidos a un segundo ensayo. El ensayo de los muros tanto en condición sana como reparada, se realiza aplicando una carga vertical constante y, simultáneamente, una carga horizontal alternada a la altura de la cadena, que simula las solicitaciones de tipo sísmico en un edificio de varios pisos. La carga horizontal se incrementa gradualmente hasta sobrepasar los niveles típicos de falla estructural y en el caso de los muros sanos, el ensayo se detiene cuando se ha alcanzado un nivel de daño preestablecido en el programa de reparaciones. Las soluciones que se han adoptado para la reparación de los muros, incluyen a aquellas que han presentado los mejores índices de recuperación de rigidez y resistencia en probetas a escala reducida. Estas consisten en la proyección de mortero de cemento contra la superficie de albañilería, realizada por medios neumáticos (shotcrete, mezcla seca) y en forma manual (estuco), incorporando una malla de acero de refuerzo electrosoldada, anclada a la albañilería. Este enchape se aplica por una o por ambas caras. Además, se analiza el reemplazo del paño de albañilería como técnica de reparación de uno de los muros construidos con ladrillo hecho a mano, solución que se complementa con la colocación de un refuerzo mínimo de acero entre hiladas del paño reparado. Las 3 técnicas usadas como reparación muestran un desempeño eficiente, con índices de recuperación significativos de los parámetros de resistencia y rigidez. En el caso de la reparación con enchape, tanto por una como por ambas caras, el aumento de resistencia es tal que la falla del muro ya no se asocia a corte en el paño, como en el ensayo de muro sano, sino que al sobre-esfuerzo axial de los pilares por efecto de rotación global. Por su parte, el reemplazo del paño de albañilería, con la colaboración del refuerzo horizontal, otorga al muro reparado una significativa capacidad de respuesta posterior al agrietamiento, que anula el efecto de falla frágil de la albañilería.

La presente tesis muestra de manera comparativa los distintos tipos de sostenimiento que se usan actualmente en la Mina Cobriza. Tomamos como referencia además el uso del Shotcrete vía húmeda como método de ensayo, por ser este un sistema de sostenimiento relativamente nuevo usado por Doe Run desde el año 1999 hasta la actualidad en las labores de la Mina Cobriza su principal unidad de explotación y productor de concentrado.

Blast loads on buildings can originate from accidental explosions or from targeted attacks. Design against blast loads has become an increasingly important topic due to the current political climate. Unfortunately, many older buildings are constructed with unreinforced masonry (URM) walls which are particularly susceptible to out of plane failures caused by blast loads. One solution to increase the safety of these buildings is to retrofit them with advanced materials that can increase their out-of-plane stiffness and resistance. This thesis investigates the potential of using a high-performance shotcrete as a retrofit system for URM walls against blast effects. The shotcrete used in this study is made from Engineered Cementitious Composite (ECC), a special type of fiber-reinforced cementitious material, with high ductility and high energy-absorption capacity. The ECC shotcrete replaces aggregates with synthetic microfibers to increase tensile strength and ductility. A welded wire mesh was embedded in the shotcrete to provide ductile behavior. The testing program includes a total of six large-scale unreinforced masonry wall specimens. Two walls were constructed using concrete masonry unit (CMU) blocks to be retrofitted. The first specimen was built as an infill wall, experiencing no axial load, while the second specimen was built as a load bearing wall, with 10% axial load. Four more walls were built out of stone blocks. Two of the stone walls were controls: one infill and one load bearing (4% axial load). The other two stone walls were retrofit with the shotcrete system: one infill and one load bearing (4% axial load). The blast loads were simulated using the University of Ottawa’s Shock Tube. The walls were restrained at the top and bottom with a shear restraint to induce one way bending. Pressure, displacement and strain data were acquired with the use of pressure gauges, LVDT’s, strain gauges and cameras. The specimens were subjected to gradually increasing blast pressures until failure. The performance of the specimens was observed by analyzing the displacement, crack widths, fragmentation and failure mode. The results indicate the benefits of using ECC shotcrete as a retrofit system. The displacements of the retrofit walls were very small compared to the control walls, and fragments were limited. The specimens with axial load were found to have increased resistance. While the failure mode was brittle for the retrofit walls, this can be avoided with the use of a mesh with a larger area of steel. A SDOF analysis was performed to predict the blast response of the test walls. The analysis was done by generating resistance functions for the walls through analytical models. The analysis was found to agree reasonably well with the experimental data.

Ingeniero Civil / El uso del shotcrete se ha incrementado principalmente en obras mineras donde cumple una función primordial en el refuerzo de túneles. El aumento de la tecnología exige que este material se mantenga competente frente a los requerimientos de resistencia y ductilidad, para esto, el ensayo ASTM C1550-12 resulta conveniente al evaluar la capacidad de este material para absorber energía de deformación al encontrarse sometido a flexión. El ensayo consiste en inducir una carga puntual al centro de un disco de shotcrete que se encuentra apoyado en tres puntos simétricamente distribuidos en la base de éste, midiendo la fuerza y el desplazamiento en el centro. Producto de esto, se mide el área bajo la curva del gráfico carga desplazamiento, que representa la energía capaz de absorber el shotcrete como representación de su rigidez a la flexión. Esta investigación pretende realizar un modelo numérico en base a elementos finitos que reproduzca el ensayo ASTM C1550-12. De esta manera, el uso de un modelo de elementos finitos puede ser una herramienta de diseño alternativa o complementaria a los resultados experimentales. El modelo permitirá comparar la respuesta del shotcrete con diferentes refuerzos, evaluando la energía de deformación, el peak de carga, la pérdida de carga post-peak y la pendiente post-peak. Se confecciona un modelo de shotcrete sin refuerzo para obtener el módulo de elasticidad del material, posteriormente utilizado en los modelos de shotcrete reforzado con mallas geosintéticas y metálica. De forma complementaria, se confeccionan modelos para estudiar el efecto de la variación del módulo de elasticidad del shotcrete a refuerzo fijo, la importancia del espesor del refuerzo y la respuesta del sistema al variar el tipo de contacto entre el refuerzo y el shotcrete. Esto se resume en un total de 12 modelos. El modelo permite representar el comportamiento del shotcrete reforzado, con la limitación de no incluir el daño del refuerzo en el material compuesto. Sin embargo, esto no altera el comportamiento lineal de los materiales, rescatando parámetros relevantes para el diseño de este material, tales como el módulo de elasticidad y el peak de carga.

La presente investigación se propone resolver el siguiente problema general: ¿Cuál es la incidencia de la incorporación del aditivo SIKA VISCOCRETE SC - 90 en las propiedades físicas-mecánicas del shotcrete a emplear en el tajeo 500 – acceso 534 Unidad de producción Andaychagua - Volcan Compañía Minera S.A.A 2018?, planteándose como objetivo general: Evaluar la incidencia de la incorporación del aditivo SIKA VISCOCRETE SC - 90 en las propiedades físicas-mecánicas del shotcrete a emplear en el tajeo 500 – acceso 534 Unidad de producción Andaychagua - Volcan Compañía Minera S.A.A 2018, y como hipótesis a contrastar: La incorporación del aditivo SIKA VISCOCRETE SC - 90 inciden directamente en las propiedades físicas-mecánicas del shotcrete a emplear en el tajeo 500 – acceso 534 Unidad de producción Andaychagua - Volcan Compañía Minera S.A.A 201