  Much interest has been devoted to the shape evolution of neutron-rich Si
isotopes recently both experimentally and theoretically. We provide our study
of $^{28-42}$Si by Skyrme-Hartree-Fock model with BCS approximation for the
pairing channel. We use an empirical pairing parameter deduced from the
experimental binding energy data for each nuclei and each Skyrme
parametrization. The recent highlight of the deformation change from a prolate
shape of $^{38}$Si to an oblate shape of $^{42}$Si is confirmed in the present
model. We also emphasize the role of tensor force on deformations of
neutron-rich $^{30,32}$Si, and discuss its underlying physics.
