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ABSTRACT
The construction of large dams, currently mainly concrete faced rockfill dams, as well as high road embankments and mining deposits resulting from blasting, requires the knowledge of the mechanical behavior of roills for their design, construction, and maintenance. Significant efforts are made to study them, though most often using smaller specimens, due to the practical difficulties and high cost of large-scale equipment testing; this results in uncertainties arising from scaling implications. As a starting point, it is relevant to recognize and keep in mind the experiences and results developed in Mexico by Professor R. J. Marsal decades ago, when testing rocky fragments up to 20 cm in size using giant triaxial equipment (specimens with a diameter of 1.13 m, height of 2.5 m, confining stress up to 2.5 MPa, maximum deviatoric stress of 15 MPa), and a 1.14 m diameter oedometer to apply compressive stresses up to 10 MPa. This review is carried out as a prelude to the doctoral work of the second author, which aims to investigate the scale effect on the compressibility of an andesitic rockfill through gravel and sand. The recent results of the geotechnical characterization of a rockfill with a maximum size of 16 cm and its uniaxial compression tests in a 97 cm-diameter oedometer are presented. Likewise, the results of gravel used as scaled rockfill are shown, tested in a 38 cm-diameter, 40 cm-high oedometer. The compressibility of these specimens under different relative densities was studied, highlighting the strong influence of moisture conditions (dry and saturated). These laboratory tests confirm what has been observed and measured in the field: noticeable settlements in rockfill road embankments during the annual season of heavy rains, persisting for at least 3 years after construction.
Keywords: Rockfill, compressibility, grain breakage, rocky embankments, scaling.
Authors: Manuel J.Mendoza and Juan S. Sanabria