[en] Multi-fragments production in intermediate-energy heavy ion collisions is the most important deexcitation process for hot nuclei produced in small impact-parameter collisions (central collisions). The study of the 60 A.MeV Kr+Au system, performed at GANIL with a 4π and low threshold experimental setup including the fragments and light charged particles multidetectors DELF, XYZt, MUR and TONNEAU associated with 6 solid state detectors, has allowed to measure the global characteristics of dissipative reactions leading to a large amount (up to 6) of fragments with charge greater than 5. The events analysis has been performed by using global variables and has shown that there was the formation of a equilibrated composite system when one looked at kinematical observables (velocities) in the center-of-mass frame. The use of two models, one corresponding to multifragmentation, the other to sequential binary fission, has allowed to conclude for the existence of a simultaneous breakup of the composite system (multifragmentation). Last, no effect related to nuclear matter compressibility (compression/expansion stage) has been found for the most important part of the fragments (charge greater than 10). (orig.)