When should I choose pipe ramming as my preferred trenchless method?

Pipe ramming is a trenchless construction technique used to install horizontal underground pipes, ducts, and culverts. This method involves using a ramming tool (which is essentially an enclosed piston) to drive the structure into the ground, from the launch pit to the exit pit, by applying continuous high-frequency percussive blows.

One of the main reasons to consider pipe ramming is when installations are required to occur under existing infrastructure such as roadways, buildings, railways, etc. Pipe ramming can also be used to install utilities under protected natural landscapes such as rivers and forested areas. Conventional open-cut methods of pipeline installation are highly destructive and occupy a large site footprint.

This can lead to inconvenient disruptions, extensive restoration works, and non-compliance with environmental standards in some applications. Pipe ramming allows underground installations to occur with minimal ground disturbance, thus resulting in less impact on the surrounding environment and significantly reduced restoration costs.

Although other trenchless techniques, such as horizontal directional drilling, can be used to perform underground pipe and utility installations, there are situations where pipe ramming methods may be more appropriate. One of the main concerns with trenchless boring methods is soil heaving. The removal of soil during boring relieves the stresses in the soil, resulting in an upward movement in some soil types.

Settlement is also known to occur, since the removal of soil from can also cause layers above bore to move downward due to diminished support and weakened soil structure. These are phenomena mainly present in over-excavations associated with horizontal directional drilling.

In pipe ramming, the limits of the excavation are limited to within the pipe or casing, with the “excavated” soil removed from the casing’s interior after installation. This results in minimal disturbance to surrounding soil and no over-excavations; thus, any settlement likely to occur as a result of ramming is negligible. Additionally, soil heaving is generally not an issue during pipe ramming since very little soil is displaced as the casing is advanced.