  We study the approach to global breakdown in disordered media driven by
increasing external forces. We first analyze the problem by mean-field theory,
showing that the failure process can be described as a first-order phase
transition, similarly to the case of thermally activated fracture in
homogeneous media. Then we quantitatively confirm the predictions of the
mean-field theory using numerical simulations of discrete models. Widely
distributed avalanches and the corresponding mean-field scaling are explained
by the long-range nature of elastic interactions. We discuss the analogy of our
results to driven disordered first-order transitions and spinodal nucleation in
magnetic systems.
