The soil displacement technique with non-steerable hammers

The soil displacement technique is a method for the trenchless installation of pipes which is usuccessfully used for the last four decades. The soil displacement hammer, driven by compressed air, creates a channel ready for pulling in short or long pipes made of plastic (PE, PVC or PE-X) up to ND 200, but also any type of cable in lengths up to 40 m (depending on the soil quality), either simultaneously or in a second working step. This allows trenchless traffic route crossings as well as the installtion of house service connections for gas water, etc. right on target and completely without trenches 

Conditions of application

The soil to be penetrated must be sufficiently displaceable. The soil displacement hammer is placed on a starting cradle and launched from out of a pit. By means of a telescopic sight, aim is taken and the height and sides of the machine are adjusted. The soil displacement hammer is moved forward by a piston driven with compressed air (normal job site compressor). External friction is required for the forward movement. If this is missing, in loose, soft soils for example, external static support can be added.
 

Two basically different systems are possible:

1. Either the piston applies impact to the casing and drives the complete displacement hammer and the attached pipe string forward with one blow (rigid system) or
2. The piston first strikes the mobile multi-cutter cone and then the casing, which means that the soil displacements hammer moves forward in two steps.

The soil displacement hammers achieve an installation speed of 15 m/h, depending on the soil. The cover should be at least ten times as thick as the diameter of the casing to avoid arching of the surface. The soil displacement machines are equipped with a reversing gear. The Grundomat with its mobile multi-cutter cone is simply reversed with a lever. A plug-on head with integrated transmitter or a built-in transmitter in the hose makes localisation possible, but is not intended for steering. The soil displacement method is described in the German guideline ATV-A 125 and in the GW 304 Pipe Laying as well as in other German standards.

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