29 is opened see fig6 and the module 2 is launched guided by said thrust roller units 32 and pushed by the driving system 53 the driving system 53 comprises a transversal thrust beam 54 see specifically fig1 through 13 which by transversely crossing the basin 1 has its ends inserted between two mutually opposite wings 55 and 56 of two longitudinal double 34 l 34 shaped guide beams 57 and 58 which are provided with equidistant and mutually opposite holes 59 which run throughout the length of the basin 1 each of said ends of the thrust beam 54 is then connected with hydraulic double effect hydraulic thrust cylinders 60 two of which are visible in the figures the pistons 61 of the cylinders 60 are linked with a block 62 equipped with two vertical and mutually opposite hydraulic jacks 63 and 64 see fig1 suitable for inserting the two teeth 65 and 66 into said mutually opposite holes 59 of the wing 55 and the wing 56 of the guide beams 57 and 58 respectively in this way by inserting the teeth 65 and 66 into the holes 59 so as to fix the blocks 62 in position and by extracting the pistons from the hydraulic thrust cylinders 60 the thrust beam 54 and consequently the module 2 are displaced forwards then by disconnecting the blocks 2 and retracting the pistons.