MINERÍA la mejor puerta de acceso al sector minero MINERÍA / SEPTIEMBRE 2022 / EDICIÓN 540 124 be discussed later, the soil peak shear strength is found to occur at a shear strain of approximately 5%. Consequently, unit stress at 5% strain will lead to improved performance. This is because although the tensile capacity of geogrids may continue to develop beyond a 5% strain, the soil shear strength would have already been achieved. Therefore, a relevant parameter to consider when comparing the different products is the secant stiffness at a tensile strain of 5%. With a secant stiffness of 6,240 kN/m, Geogrid 4 is the product that provides the best displacement compatibility with the fill soil. Geogrid 1 and Geogrid 1 provide a secant stiffness of approximately 3,500 kN/m. Finally, Geogrid 2 and Geogrid 3 provide a secant stiffness of less than 2,500 kN/m. Chemical resistance to acidic soils: an important aspect to consider in the selection process, which is directly related to the raw polymeric material used in the manufacture of geogrids, is related to the chemical resistance of the products. While polyester (PET) is susceptible to chemical degradation in basic environments (pH greater than 10) and acidic environments (pH less than 2), polyvinyl alcohol (PVA) offers comparatively high chemical resistance in both highly basic and acidic environments. While the actual borrowing source of the fill material may not be precisely defined, there is concern that the fill used in the geogrid-reinforced slope may possibly involve a comparatively acidic environment. Consequently, polymeric materials such as PP, HDPE and PVA will provide better chemical resistance than PET. Among the geogrids considered in this project, Geogrid 4 is the only product manufactured with a polymer that resists acidic environments (PVA); all other products are manufactured using PET, as this material allows manufacture of the high-strength geogrids required for this project. No PP or HDPE products have been identified that meet the tensile strength requirements for this project. Direct Shear Test of the Soil Direct shear tests of the soil (ASTM D3080) were conducted using samples sieved to a maximum particle size of ¾”. Tests were carried out at four different confining pressures (198, 400, 600, and 800 kPa). The tests were carried out in submerged conditions (with container flooded one hour before the start of the shear). Conditioning of the soil specimen involved application of the normal stress for a period of 15 minutes before shearing. The shear displacement rate was 0.1 mm/ min, which was considered adequate to minimize the development of pore water pressures. The lower half of the direct shear box had dimensions of 457 x 305 mm and was sheared against a smaller fixed container (the upper half with dimensions of 305 x 305 mm). Otras dos consideraciones son importantes para la elevación del dique Pampa Verde: Compatibilidad de las deformaciones del suelo y de la geomalla: como se verá más adelante, el pico de resistencia al cizallamiento del suelo se produce con una deformación de aproximadamente el 5%. Por lo tanto, el esfuerzo específico al 5% de deformación conducirá a un mejor desempeño. Esto se debe a que, aunque la capacidad de tracción de las geomallas puede seguir desarrollándose más allá de una deformación del 5%, la resistencia al corte del suelo ya se habría alcanzado. Por lo tanto, un parámetro relevante a tener en cuenta a la hora de comparar los diferentes productos es la rigidez secante a una deformación por tracción del 5%. Con una rigidez secante de 6240 kN/m, la Geomalla 4 es el producto que proporciona la mejor compatibilidad de desplazamiento con el suelo de relleno. Las Geomallas 1 y 5 proporcionan una rigidez secante de aproximadamente 3,500 kN/m. Por último, las Geomallas 2 y 3 proporcionan una rigidez secante inferior a 2,500 kN/m. Resistencia química a los suelos ácidos: un aspecto importante a tener en cuenta en el proceso de selección, que está directamente relacionado con la materia prima polimérica utilizada en la fabricación de las geomallas, está relacionado con la resistencia química de los productos. Mientras que el poliéster (PET) es Figuras 5 (a) a la (e). Respuesta de la interfaz de esfuerzo cortante frente al desplazamiento utilizando las Geomallas 1 a la 5, respectivamente.
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