Theoretical and experimental investigations of the physical principles of multibunch dielectric wakefield accelerator concept based on the wakefield excitation in the dielectric structure by a sequence of relativistic electron bunches are presented. The purpose of the concept is to enhance the wakefield intensity by means of the multibunch coherent excitation and wakefield accumulation in a resonator. The acceleration of bunches is achieved at detuning of bunch repetition frequency relative to the frequency of the excited wakefield. In such a way the sequence of bunches is divided into exciting and accelerated parts due to displacing bunches into accelerating phases of wakefield excited by a previous part of bunches of the same sequence. Besides the change of the permittivity and loss tangent of dielectrics under the irradiation by 100MeV electron beam is studied.