Publication: EFECTOS DE LA INTERFAZ ROCA/RELLENO EN EL PROCESO DE CONSOLIDACI´ON DE RELAVES CEMENTADOS DISPUESTOS INTERIOR MINA
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Date
2019
Authors
GONZÁLEZ PIZARRO, DIEGO MATÍAS
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Abstract
La técnica de disposición de rellenos de relaves cementados (CPB), consiste en disponer una mezcla
de relaves, agua y cemento al interior de minas subterráneas con el objetivo de aumentar la estabilidad
del macizo rocoso, recuperar pilares mineralizados entre caserones y disminuir el impacto medio
ambiental de los depósitos superficiales de relaves. La incorporación de cemento a la mezcla produce
una variación de las propiedades mecánicas del relleno en la medida que el tiempo transcurre, lo que
afecta el desarrollo de esfuerzos al interior de material y por tanto en las paredes del caserón (macizo).
En la práctica, el estado tenso-deformacional del relleno es estudiado a través de soluciones analíticas
y modelos numéricos. Sin embargo, una de las limitaciones de los modelos actuales, es que no
incorporan todos los fenómenos que afectan al relleno durante su curado (cementación). Dicho lo anterior,
es que el presente estudio busca explorar numéricamente la respuesta tenso-deformacional de
rellenos con pasta cementada incorporando fenómenos avanzados de respuesta, con énfasis en el efecto
arco. Para estos efectos, se realizarán una serie de modelos en el software de diferencias finitas Flac3D,
incorporando los efectos de hidratación del cemento, disipación de presión de poros, geometría de la
interfaz, elementos de interfaz y movimiento de las paredes del caserón (“wall closure”). Los modelos
consideran un relleno de pasta cementada rodeada de un macizo rocoso, los cuales son caracterizados
mediante un modelo Mohr-Coulomb y modelo de respuesta elástico, respectivamente. La interfaz
entre el relleno y la roca se caracteriza mediante un modelo bi-lineal de Coulomb. Se consideró una
grilla compuesta por elementos poliédricos tipo “brick” y “wedge”, la cual alcanza una dimensión en
la interfaz entre el relleno y la roca de 0, 2 [m].
A partir de los modelos generados, se observa que los factores más relevantes en el desarrollo de
esfuerzos son la consolidación, envejecimiento del cemento, tipo de drenaje considerado y el movimiento
de las paredes del macizo rocoso. Estos factores producen un impacto importante en el estado
tenso-deformacional del relleno, obteniendo una mayor reducción de esfuerzo al interior del caserón,
comparado con un modelo que se caracteriza mediante propiedades constantes y sin consolidación.
Estos resultados se pueden interpretar como un aumento del esfuerzo de corte en la interfaz, lo cual se
traduce en una mayor transferencia de esfuerzo vertical desde el relleno al macizo rocoso. Esto permite
a su vez observar con mayor claridad el fenómeno de efecto arco que se produce al interior del caserón.
Los resultados obtenidos permiten demostrar que es necesario la incorporación de varios factores al
momento de la modelación numérica de este tipo de problemas, con el objetivo de reproducir con una
mayor precisión el comportamiento de los rellenos de pasta cementadas en etapas tempranas y en
etapas de exposición lateral.
Cemented paste backfilling is a technology that consists in filling the underground open voids left after ore mining (blasting, “mucking”, etc) with a mixture of full stream mine tailings, water, cement and sometimes other aggregates. The use of this technique improves rock stability and allows for pillar recovery. In addition to this, it decreases the impact of the disposal of tailings on the earth’s surface. The addition of cement has a significant impact on the mechanical properties and response of the backfill. The state of stress along backfilled stopes has been studied in the past through analytical solutions and numerical models. However, one of the limitations of these solutions is that they do not consider all the phenomena that affect the fills during its curing. Regarding this, the present study explores the stress-strain state of CPB using numerical modeling in order to considered advanced response phenomena with emphasis on the arching effect. To accomplish this, a series of numerical models are developed in the finite difference software Flac3D, including the effects of cement hydration, pore pressure dissipation, interface geometry, interface elements and mining induced wall closure on the response of backfilled stopes. The models consider a cemented paste backfill surrounded by rock mass, which are characterized by Mohr-Coulomb and elastic models, respectively. The interface between the fills and the rock mass is characterized by a bi-linear Coulomb model. A grid composed by polyhedral elements “brick” and “wedge” was considered. Dimension of the interface was equal to 0, 2 [m]. From these models, it was observed that the most influential factors in the development of stresses within the fill are the consolidation process, aging of the cement, type of drainage and wall closure movements. These factors produce an impact in the stress strain state of the backfill, resulting in a significant reduction of vertical and horizontal stresses when compared with models characterized by constant properties and without considerations to the flow of water. It clearly observed an increase in the shear stress at the rock-CPB interfaces, which results in a greater transference of vertical stress from the filling to the rock mass. This allows to clearly observe the phenomena of arching effect inside the stope. The results from this study show that is necessary to incorporate in routinary designs the advanced response phenomena of backfills into numerical models. This may improve the safety and dosification of the fills in the backfilling practice.
Cemented paste backfilling is a technology that consists in filling the underground open voids left after ore mining (blasting, “mucking”, etc) with a mixture of full stream mine tailings, water, cement and sometimes other aggregates. The use of this technique improves rock stability and allows for pillar recovery. In addition to this, it decreases the impact of the disposal of tailings on the earth’s surface. The addition of cement has a significant impact on the mechanical properties and response of the backfill. The state of stress along backfilled stopes has been studied in the past through analytical solutions and numerical models. However, one of the limitations of these solutions is that they do not consider all the phenomena that affect the fills during its curing. Regarding this, the present study explores the stress-strain state of CPB using numerical modeling in order to considered advanced response phenomena with emphasis on the arching effect. To accomplish this, a series of numerical models are developed in the finite difference software Flac3D, including the effects of cement hydration, pore pressure dissipation, interface geometry, interface elements and mining induced wall closure on the response of backfilled stopes. The models consider a cemented paste backfill surrounded by rock mass, which are characterized by Mohr-Coulomb and elastic models, respectively. The interface between the fills and the rock mass is characterized by a bi-linear Coulomb model. A grid composed by polyhedral elements “brick” and “wedge” was considered. Dimension of the interface was equal to 0, 2 [m]. From these models, it was observed that the most influential factors in the development of stresses within the fill are the consolidation process, aging of the cement, type of drainage and wall closure movements. These factors produce an impact in the stress strain state of the backfill, resulting in a significant reduction of vertical and horizontal stresses when compared with models characterized by constant properties and without considerations to the flow of water. It clearly observed an increase in the shear stress at the rock-CPB interfaces, which results in a greater transference of vertical stress from the filling to the rock mass. This allows to clearly observe the phenomena of arching effect inside the stope. The results from this study show that is necessary to incorporate in routinary designs the advanced response phenomena of backfills into numerical models. This may improve the safety and dosification of the fills in the backfilling practice.
Description
Keywords
RELLENOS DE PASTA CEMENTADA , MODELO NUMERICO , INTERFAZ RELLENO-ROCA