The intermediate pipe jacking method uses the blows of an air hammer to drive the pipe through the earth while parts of the pipe are supported by jacks. The leading edge of the pipe is usually open and is typically closed only when smaller pipes are being installed. The shape allows a small overcut to alleviate friction between pipe and soil, thus relieving strain on the pipe.
This directs the soil into the pipe itself, filling it with the bore’s spoil. Special equipment attached to the pipe prevents the spoil from sticking to the pipe, and the spoil is removed after the section of pipe is in place.
In intermediate pipe jacking, the forward sections of pipe are supported by large, heavy-duty jacks placed under the middle of the pipe in the intermediate area of the pipe, but not at the ends. A specialized air hammer then begins to rain blows on the trailing edge of the pipe, driving it into the earth.
As the trailing edge of the pipe nears the bore, the jacks are lowered and the last section of pipe is attached to the first section (remember, this is a rehab process, not an initial installation).
The subsequent or last (if it's a small repair) section of pipe isn't supported by jacks; rather, after its leading edge is attached to the pipe already in the bore, its trailing edge rests on the cradle in the launching pit. It's driven into the bore while crew members clear the spoil from the forward section of pipe.