  Insight into the blockage vulnerability of evolving spatial networks is
important for understanding transport resilience, robustness, and failure of a
broad class of real-world structures such as porous media and utility, urban
traffic, and infrastructure networks. By exhaustive search for central
transport hubs on porous lattice structures, we recursively determine and block
the emerging main hub until the evolving network reaches the impenetrability
limit. We find that the blockage backbone is a self-similar path with a fractal
dimension which is distinctly smaller than that of the universality class of
optimal path crack models. The number of blocking steps versus the rescaled
initial occupation fraction collapses onto a master curve for different network
sizes, allowing for the prediction of the onset of impenetrability. The
shortest-path length distribution broadens during the blocking process
reflecting an increase of spatial correlations. We address the reliability of
our predictions upon increasing the disorder or decreasing the fraction of
processed structural information.
