  We study the effect of squark-generation mixing on production and decays of
squarks and gluinos at LHC in the Minimal Supersymmetric Standard Model (MSSM).
We show that the mixing effects can be very large in a significant range of the
squark-generation mixing parameters despite the very strong constraints on
quark-flavour violation (QFV) from experimental data on B mesons. We find that
under favourable conditions the QFV decay branching ratio B(gluino -> c bar{t}
(t bar{c}) neutralino_1) can be as large as about 50%, which may lead to
significant QFV signals at LHC. We also find that the squark generation mixing
can result in a novel multiple-edge (3- or 4-edge) structure in the charm-top
quark invariant mass distribution. Further we show that the two lightest
up-type squarks ~u_{1,2} can have very large branching ratios for the decays
~u_i -> c neutralino_1 and ~u_i -> t neutralino_1 simultaneously due to the
mixing effect, resulting in QFV signals 'pp -> c bar{t} (t bar{c}) +
missing-E_T + X' at a significant rate at LHC. These remarkable signatures
could provide a powerful test of supersymmetric QFV at LHC and could have an
important impact on the search for squarks and gluinos and the determination of
the MSSM parameters at LHC.
