Pipe Ramming
Pipe Ramming
Whilst basically being the same type of machine, the ramming hammer is used in different way altogether. As opposed to using the impact energy to displace soil directly around the outer shell of the unit, a ramming hammer's energy is used to push a steel pipe section into the ground from a start pit. The pipe installed can be used either as a pipe in itself or as a carrier conduit for separately installed services.
On a typical installation the first section of steel pipe is placed in the start pit on the correct line and level for the installation. The ramming hammer is attached, via a series of size adaption collets, to the rear of this pipe. The hammer is operated and the reciprocating piston drives the pipe section forward directly into the ground. Ground conditions on such a project are vital to the success of such work and should be very well understood before attempting such an installation.
Normally, installations are achieved using an open-ended pipe so that the cutting edge is only that of the pipe (which is often fitted with a cutting edge before commencing the ram). The ground into which the pipe is rammed then forms a plug inside the pipe. When ramming over the required distance is complete this soil is removed using either comapressed air pressure, water jets or scrapers, leaving the pipe in place as required. As with impact molng the ground conditions and unexpected obstacles can cause the pipe to deflect from the required course. So, the system is often used only where precise line and level tolerences are not required. Installations of up to 3,000 mm have been rammed using this technique. Depending on the final use of the pipe, various supporting installation devices have been developed. Details should be obtained from the manufacturers.
Ramming can also be achieved using closed end pipes where ground conditions may not be condusive to open ended techniques.
Another area in which ramming hammers has been utilised successfully is the installation of a 'Pipe Arch'. Pipe Arches are utilised where a series of casing pipe are rammed into the ground, often below road ways or rail tracks, to form a preliminary support mechanism separating the ground inside the arch from that surrounding it. Once the pipe arch is competed, the soils within the pipe arch are excavated within the confines and safety zone created by the arch, minimising the potential for ground movement during excavation and reducing the potential for subsidence at surface and therefore in the infrastructure beneath which the new tunnel will pass.