Diseño, construcción y prueba de una caja para cizallar suelos
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Date
2008
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Universidad de Concepción
Abstract
El objetivo de este trabajo fue diseñar, construir y probar una caja de cizalle torsional, que permita obtener el coeficiente de fricción y ángulo de fricción interna de un suelo in situ. Para ello se propuso simular en la medición la carga ejercida por un tractor con implementos sobre el suelo, que según Cornejo (1999) es máxima en tractores de 4WD y corresponde a 446 kPa. Se utilizaron los datos de coeficiente de fricción y ángulo de fricción interna presentados por Ashburner y Sims (1984) para obtener los pares de torsión máximos en cada tipo de suelo; con el máximo de estos, se dimensionó la caja. El diámetro y altura se determinaron considerando un volumen mínimo de muestra para lograr no disturbar el suelo de acuerdo a Hartge y Ellies (1999). Para obtener sobre la caja una carga que simule el peso de un tractor con implementos, se diseñaron los siguientes elementos: dos anclajes, una viga porta anclaje y viga, que sirven de soporte para lograr, indirectamente, una reacción sobre la caja, aplicando el principio de la palanca interresistente (Máximo y Alvarenga, 1998). De acuerdo al diseño, se construyó el equipo, y se determinaron los parámetros de la ecuación de Coulomb (Sánchez-Girón, 1996) para un suelo agrícola representativo de la provincia de Ñuble, con dichos datos se graficó la curva de esfuerzo de corte versus esfuerzo normal. Se estableció un procedimiento para la utilización del equipo, el cual permite lograr las curvas de esfuerzo de corte versus esfuerzo normal sin inconvenientes, simulando el paso de un tractor con implementos.
The objective of this work was to design, to construct and to test a torsional shear box that will be used to obtain the friction coefficient and the internal friction angle of a soil in situ. In order to achieve this objective the load exerted by a tractor with implements upon the soil was simulated. These loads, according to Cornejo (1999) is maximum in 4WD tractors and can reach 446 kPa. The data about friction coefficient and internal friction angle presented by Ashburner and Sims (1984) were used to obtain the maximum torsional torque in each soil type to calculate de box dimensions. The box diameter and height were determined considering the minimum not disturbed soil sample volume, according to Hartge and Ellies (1999). To obtain upon the box a load that simulates the weight of a tractor and implement the following elements were designed: two anchors, an anchors supporting beam, and a beam; they, indirectly, create a reaction upon the box by applying the principle of the inter resistant lever (Máximo and Albarenga, 1998). According to this design the equipment was constructed and the Coulomb equation parameters were determined (Sanchez-Girón, 1996) for a soil representative of the province of Ñuble; with these data the curve shear stress versus normal stress was drawn. A procedure to use the equipment was also established to facilitate its use in the field in order to obtain the curves mentioned before.
The objective of this work was to design, to construct and to test a torsional shear box that will be used to obtain the friction coefficient and the internal friction angle of a soil in situ. In order to achieve this objective the load exerted by a tractor with implements upon the soil was simulated. These loads, according to Cornejo (1999) is maximum in 4WD tractors and can reach 446 kPa. The data about friction coefficient and internal friction angle presented by Ashburner and Sims (1984) were used to obtain the maximum torsional torque in each soil type to calculate de box dimensions. The box diameter and height were determined considering the minimum not disturbed soil sample volume, according to Hartge and Ellies (1999). To obtain upon the box a load that simulates the weight of a tractor and implement the following elements were designed: two anchors, an anchors supporting beam, and a beam; they, indirectly, create a reaction upon the box by applying the principle of the inter resistant lever (Máximo and Albarenga, 1998). According to this design the equipment was constructed and the Coulomb equation parameters were determined (Sanchez-Girón, 1996) for a soil representative of the province of Ñuble; with these data the curve shear stress versus normal stress was drawn. A procedure to use the equipment was also established to facilitate its use in the field in order to obtain the curves mentioned before.
Description
Tesis presentada para optar al título de Ingeniero Civil Agrícola
Keywords
Cohesión, Maquinaria agrícola, Herramientas de corte