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The efficient excavatability of ground is an issue that has still to be fully resolved. Although many existing criteria currently address this problem, they do not coincide with respect to the question whether mechanical methods are better than drilling and blasting for a specific type of ground. This is undoubtedly due to the variety of parameters involved. In the present study, ground in which a cut was to be made was chosen in order to compare the different existing criteria, highlighting the differences between them. To carry out this study, numerous laboratory and field trials were conducted, including the performing of mechanical tests to select the optimum method for excavating the ground in the area under study.

This paper analyzes the stability of the Llerin rockfill dam using Barton–Kjaernsli's shear criterion. To fit the parameters of this criterion, a direct shear test was designed that allows in situ calculation, using large-size samples of the shear stress at which failure is produced for different normal loads. These experimental values are then used to obtain more reliable values for the friction angle and the equivalent roughness of the rockfill material. The rockfill of Llerin dam is formed by a suitably ground gonfolite limestone rockfill that serves as a contention dam for a lagoon of mine tailings. The experimental results obtained in in situ tests were compared with those predicted by the shear criterion, subsequently determining the safety coefficient of the rockfill dam using the SLOPE computer program. We conclude that the values estimated via in situ testing permit the behaviour of the containment dam to be predicted more accurately.