The ground-level enhancement (GLE) events are often
associated with the large gradual solar events such as fast coronal
mass ejections (CMEs), but not all fast CMEs lead to GLE events. We
suggest that GLE would be associated with processes of the multiple
CMEs interactions. Here we proposed a ``multiple-shock'' scenario
driven by the ``continuous-CME'' sympathetically, in which the
posterior shocks catch up with the preceding shock and have pileup
collisions. We simulate the ``multiple-shock'' by applying a
dynamic Monte Carlo method in present work. In the
``multiple-shock'' scenario, the seed energetic particles produced
by the preceding shock can be injected into the posterior shocks for
cascaded acceleration efficiently. We obtain the detailed SEP energy
spectrum with different behaviors at the related episodes of the
``multiple-shock'' evolution. As results, we find the pileup
collisions of the ``multiple-shock'' dominate multiple``concave''
energy spectral slope in the generated SEP event.