In the construction industry, moling is a trenchless method used to lay pipes.
During the moling process, a pneumatically-driven machine – known as a mole – forces its way through the soil along the desired path of the pipe. Moling avoids the need to dig a trench and can be used to lay water pipes, the heating coils of heat pump systems, gas pipes, conduit for electrical wire and some types of drainage.
Impact Moling (or Trenchless Technology) is a way of installing new pipes, cables and ducts without the need for continuous trenches to be dug.
Instead pits are excavated at intervals for the mole to be placed. The mole is then entered into the earth on the horizontal face at the bottom of the pit. Destination pits of similar proportions are also dug, and this is where the mole emerges. The mole itself is a steel cylinder, it works as a pneumatic cylinder with pulsed compressed air causing the head of the mole to repeatedly hammer against the soil in front of the mole. The mole displaces the soil creating a bore for the new services to then be pulled through. This reduces the installation time, disturbance and cost.
Potable water mains are typically not buried as deep in the ground, can be installed on varying grades and operate under pressure. Therefore, simple excavation and replacement can be as cost-effective as trenchless methods, in some cases. However, many choices for trenchless renewal technologies exist today for water mains and more are being developed.