Abstract: A reinforced horizontal slab having high bearing strength is created on the surface of the ground by initially forming a plurality of discrete vertically elongated reinforced zones in situ in the ground with their tops adjacent ground level and then covering the ground over and between the zones with a surfacing material constituting a slab that rests on the tops of said zones and on the ground therebetween. Each zone is a downwardly tapered concrete column having at least one vertically oriented reinforcing metal bar embedded therein.

Abstract: A method and equipment for constructing a fluid-impervious underground wall by vertically sinking an elongated web member into the ground where the wall is to be created, the sinking being performed with the aid of vertical vibration of the web member at a frequency that loosens the structure of the soil. The web member thereafter is vertically withdrawn while being vibrated vertically at the same or a higher frequency. As the web member is being sunk, liquid grout is introduced under pressure beneath the downwardly moving lower edge of the web member, such grout being forced into the surrounding soil structure by the tamping effect of said vibrating lower edge.