The proposed method involves deploying and activating three ground improvement machines together in a triangular array, rather than a single machine working alone in isolation. The machines are of the type both capable of producing vibratory excitation, and also a pump capable of creating fluid flow, in the ground at depth. Each of the three machines is independently controlled so as to create ground vibrations which are either in, or out, of phase, and at the same time create the hydraulic gradient required to cause fluid flow and seepage forces in the ground within their compass.