The random nature of geomaterial tensile strength, combined with a softening behaviour, leads to a strong and systematic dependency of the first crack stress value on the loaded volume. This problem is so important that the predictive capability of efficient damage models can be occulted by the phenomenon. The method proposed here allows this aspect to be efficiently considered in a non-linear finite element context thanks to a variant of the Weibull theory, in which the classical weakest link theory is rearranged in a non-local form permitting a second gradient implementation.