The installation of new, or replacement of existing utility mains and services can create major disruption to the surrounding environment. This disruption can be in the form of road closures, traffic hold up, noise pollution and even effects on the environment associated with the increased use of in-fill materials and land fill requirements. The use of Trenchless/No-Dig/Limited-Dig technology provides utility and construction companies with the means to complete new and replacement works with minimal disturbance to the surrounding ground surface, traffic and the environment.

Impact moling is a technique in which a percussive mole (soil displacement hammer) is launched from an excavation to displace the soil and form a bore.

The new conduit is normally drawn in behind the mole or pulled back into the bore using the hammers reverse action. Pneumatically driven moles, in which the soil is displaced by the action of a percussive piston, have been developed in the range 30 - 180mm diameter for a single operation, with repetitive multiple passes to achieve 200 - 250mm diameter.

Utility companies and their contractors use moles on a daily basis to lay new or replace existing services usually up to about 63mm diameter. However, larger bores are also common laying pipes up to 180mm, with lengths sometimes exceeding 40m.

Piling is a technique by which crimped end tubular steel casings are driven into the ground to form foundations or for underpinning applications. Piles are either top or bottom driven with a pneumatic mole.

Pipe ramming is a simple technique utilising a pneumatic hammer to drive steel casings through the ground from one pit to another. Rams of pipes up to and over 2m diameter and exceeding 70m in length have been achieved.

Pipe Bursting is a method of on-line replacement of fracturable pipe usually from excavations 10-200m apart. Extensive proving work by the gas and water industries has demonstrated the feasibility of upsizing gas mains, water mains and sewers.

An expanding device which, may be either pneumatic or hydraulic, is introduced into the defective pipeline, shattering the pipe and drawing in the new line behind it. Insertion of short lengths may be made from pits but this involves jointing of the pipeline within the pit.

This can be avoided by the use of silt trenches to insert pipe strings. Upsizing from 100mm to 225mm diameter is now well established, and pipes of up to 600mm diameter and greater have been replaced.

Bursting Technique.pdf (0.46Mb) > PDF

Techniques by which continuous or discreet pipes are inserted within existing pipes: examples include the pulling in of long lengths of PE pipes within water mains or the insertion of individual pipes within sewers.

This is generally a low cost technique, which has the disadvantage of reduction of bore.