  We present an analytic model for clustered supernovae (SNe) feedback in
galaxy disks, incorporating the dynamical evolution of superbubbles formed from
spatially overlapping SNe remnants. We propose two realistic outcomes for the
evolution of superbubbles in galactic disks: (1) the expansion velocity of the
shock front falls below the turbulent velocity dispersion of the ISM in the
galaxy disk, whereupon the superbubble stalls and fragments, depositing its
momentum entirely within the galaxy disk, or (2) the superbubble grows in size
to reach the gas scale height, breaking out of the galaxy disk and driving
galactic outflows/fountains. In either case, we find that superbubble
breakup/breakout almost always occurs before the last Type-II SN ($\lesssim$40
Myr) in the recently formed star cluster, assuming a standard high-end IMF
slope, and scalings between stellar lifetimes and masses. The threshold between
these two cases implies a break in the effective strength of feedback in
driving turbulence within galaxies, and a resulting change in the scalings of,
e.g., star formation rates with gas surface density (the Kennicutt-Schmidt
relation) and the star formation efficiency in galaxy disks.
