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Análisis de rendimiento de la cántara de una draga de succión en marcha en función de la granulometría del material transportado

ABSTRACT El proceso de sedimentación en la cántara de una draga de succión en marcha es muy complejo pero, a pesar de ello, actualmente existen modelos basados en la aplicación de las distintas teorías experimentales sobre la difusión turbulenta del material en tanques de sedimentación [Camp (1936) o Dobbins (1944)], que pueden ser aplicados con bastante aproximación, como se comprobará en este artículo, siempre que se tengan en cuenta algunas consideraciones. Se han aplicado dichos modelos a una obra de dragado hidráulico, en la que se transportaron 5 tipos de materiales de distinta granulometría. El objetivo era observar los rendimientos totales del proceso de llenado tomando como base los datos obtenidos durante la ejecución de la obra. Para ello se han calculado las velocidades de sedimentación de los distintos materiales transportados en la cántara al objeto de relacionarlas con las dimensiones de la misma para, de esta manera, comparar también los
distintos rendimientos correspondientes a cada uno de dichos materiales. Para estos materiales se ha comprobado que los resultados que se consiguen con la aplicación de las ecuaciones de Stokes y Budryck son prácticamente coincidentes cuando se emplea el modelo de Camp, lo cual es lógico dado el tipo de flujo que se produce. También se hace un análisis comparativo entre los valores de las velocidades cuando se consideran como grano individual o bien como una nube de granos. Al objeto de predecir el rendimiento de la cántara de una draga de succión en marcha, se deberían de considerar todos los casos, marcando como límites las velocidades de Stokes y Budryck por un lado y las que correspondan a la ecuación general corregida por el Nº de Reynolds obtenido por cualquiera de estas ecuaciones.
Abstract: The sedimentation process in the hopper of a trailing suction hopper dredger is very complex though, in spite of this, models are currently available based on the application of different experimental theories concerning the turbulent diffusion of the material in sedimentation tanks [Camp 1936 or Dobbins (1944)]. These theories, as shown by this article, may be applied with a reasonable degree of accuracy on the condition that these take into account certain considerations. These models have been applied to a dredging project which transported five types of material of different particle size. The objective was to
observe the total performance of the filling process on the basis of data obtained during the work. To this end, a calculation has been made of the sedimentation or settling velocity of the different materials transported in the hopper in order to relate these to the sizes of the same and, in this way, compare the different performances of each material. In these materials it has been seen that the results obtained through the application of Stokes and Budryck equations practically coincide when employing the Camp model, this being logical in view of the type of flow produced. A comparative analysis was also made between the velocities when taking the material in the form of an individual grain or as a group of grains. In order to
predict the performance of the hopper in an operating trailing suction dredger it is necessary to consider, in all cases, the velocities established by Stokes and Budryck as limit values and to consider those corresponding to the general equation corrected by the Reynolds number obtained by any of these equations.

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