  Homologous coronal mass ejections (CMEs) are an interesting phenomenon, and
it is possible to investigate the formation of CMEs by comparing multi-CMEs
under a homologous physical condition. AR 11283 had been present on the solar
surface for several days when a bipole emerged on 2011 September 4. Its
positive polarity collided with the pre-existing negative polarity belonging to
a different bipole, producing recurrent solar activities along the polarity
inversion line (PIL) between the colliding polarities, namely the so-called
collisional PIL (cPIL). Our results show that a large amount of energy and
helicity were built up in the form of magnetic flux ropes (MFRs), with
recurrent release and accumulation processes. These MFRs were built up along
the cPIL. A flux deficit method is adopted and shows that magnetic cancellation
happens along the cPIL due to the collisional shearing scenario proposed by
Chintzoglou et al. The total amount of canceled flux was
$\sim$0.7$\times$10$^{21}$ Mx with an uncertainty of $\sim$13.2$\%$ within the
confidence region of the 30$^\circ$ sun-center distance. The canceled flux
amounts to 24$\%$ of the total unsigned flux of the bipolar magnetic region.
The results show that the magnetic fields beside the cPIL are very sheared, and
the average shear angle is above 70$^\circ$ after the collision. The fast
expansion of the twist kernels of the MFRs and the continuous eruptive
activities are both driven by the collisional shearing process. These results
are important for better understanding the buildup process of the MFRs
associated with homologous solar eruptions.
