pipeline 2 but on one side thereof to control the displacement of the vehicle one or more positioning transducers 40 34 are used which are directed towards the outside of the vehicle it is pointed out that loader 80 is articulated about the spindle 82 with respect to the vehicle chassis and that its inclination can be varied by controlling jack 84 to regulate the height of fall of the rocks the other features of the vehicle are identical to those described with regard to fig2 to 4 this variant may be advantageous for placing the vehicle in its initial material unloading position because in this way the vehicle can approach pipeline 2 from the side without having to bestride it however the position regulation is possibly more difficult in the foregoing description it has been assumed that the propulsion means and vehicle chassis are linked however it is readily apparent that it may be advantageous to permit an upward or downward movement of the chassis relative to the propulsion means this makes it possible to adapt the size of the bottom of the hopper relative to the diameter of the pipeline to be covered and also to compensate to a certain extent unevennesses of the ground hereinafter three embodiments of mechanisms permitting this regulation will be described in fig6 each propulsion eans 32 is fixed by an articulated system 100 to the lower end of a post 102 which is made to slide vertically within guides 104 fixed to the chassis 30 of the vehicle these guides 104 are for example.